Re: [PATCH v5 06/11] drm/i915: Enable i915 perf stream for Haswell OA unit

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On 14 September 2016 at 15:19, Robert Bragg <robert@xxxxxxxxxxxxx> wrote:
> Gen graphics hardware can be set up to periodically write snapshots of
> performance counters into a circular buffer via its Observation
> Architecture and this patch exposes that capability to userspace via the
> i915 perf interface.
>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Robert Bragg <robert@xxxxxxxxxxxxx>
> Signed-off-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/i915_drv.h         |  72 ++-
>  drivers/gpu/drm/i915/i915_gem_context.c |  22 +-
>  drivers/gpu/drm/i915/i915_perf.c        | 998 +++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/i915/i915_reg.h         | 338 +++++++++++
>  drivers/gpu/drm/i915/intel_ringbuffer.c |  10 +-
>  include/uapi/drm/i915_drm.h             |  70 ++-
>  6 files changed, 1477 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 5fad018..551f078 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1740,6 +1740,11 @@ struct intel_wm_config {
>         bool sprites_scaled;
>  };
>
> +struct i915_oa_format {
> +       u32 format;
> +       int size;
> +};
> +
>  struct i915_oa_reg {
>         i915_reg_t addr;
>         u32 value;
> @@ -1760,11 +1765,6 @@ struct i915_perf_stream_ops {
>          */
>         void (*disable)(struct i915_perf_stream *stream);
>
> -       /* Return: true if any i915 perf records are ready to read()
> -        * for this stream.
> -        */
> -       bool (*can_read)(struct i915_perf_stream *stream);
> -
>         /* Call poll_wait, passing a wait queue that will be woken
>          * once there is something ready to read() for the stream
>          */
> @@ -1774,9 +1774,7 @@ struct i915_perf_stream_ops {
>
>         /* For handling a blocking read, wait until there is something
>          * to ready to read() for the stream. E.g. wait on the same
> -        * wait queue that would be passed to poll_wait() until
> -        * ->can_read() returns true (if its safe to call ->can_read()
> -        * without the i915 perf lock held).
> +        * wait queue that would be passed to poll_wait().
>          */
>         int (*wait_unlocked)(struct i915_perf_stream *stream);
>
> @@ -1816,11 +1814,28 @@ struct i915_perf_stream {
>         struct list_head link;
>
>         u32 sample_flags;
> +       int sample_size;
>
>         struct i915_gem_context *ctx;
>         bool enabled;
>
> -       struct i915_perf_stream_ops *ops;
> +       const struct i915_perf_stream_ops *ops;
> +};
> +
> +struct i915_oa_ops {
> +       void (*init_oa_buffer)(struct drm_i915_private *dev_priv);
> +       int (*enable_metric_set)(struct drm_i915_private *dev_priv);
> +       void (*disable_metric_set)(struct drm_i915_private *dev_priv);
> +       void (*oa_enable)(struct drm_i915_private *dev_priv);
> +       void (*oa_disable)(struct drm_i915_private *dev_priv);
> +       void (*update_oacontrol)(struct drm_i915_private *dev_priv);
> +       void (*update_hw_ctx_id_locked)(struct drm_i915_private *dev_priv,
> +                                       u32 ctx_id);
> +       int (*read)(struct i915_perf_stream *stream,
> +                   char __user *buf,
> +                   size_t count,
> +                   size_t *offset);
> +       bool (*oa_buffer_is_empty)(struct drm_i915_private *dev_priv);
>  };
>
>  struct drm_i915_private {
> @@ -2125,16 +2140,48 @@ struct drm_i915_private {
>
>         struct {
>                 bool initialized;
> +
>                 struct mutex lock;
>                 struct list_head streams;
>
> +               spinlock_t hook_lock;
> +
>                 struct {
> -                       u32 metrics_set;
> +                       struct i915_perf_stream *exclusive_stream;
> +
> +                       u32 specific_ctx_id;
> +
> +                       struct hrtimer poll_check_timer;
> +                       wait_queue_head_t poll_wq;
> +                       atomic_t pollin;
> +
> +                       bool periodic;
> +                       int period_exponent;
> +                       int timestamp_frequency;
> +
> +                       int tail_margin;
> +
> +                       int metrics_set;
>
>                         const struct i915_oa_reg *mux_regs;
>                         int mux_regs_len;
>                         const struct i915_oa_reg *b_counter_regs;
>                         int b_counter_regs_len;
> +
> +                       struct {
> +                               struct drm_i915_gem_object *obj;
> +                               struct i915_vma *vma;
> +                               u32 gtt_offset;
> +                               u8 *addr;
> +                               int format;
> +                               int format_size;
> +                       } oa_buffer;
> +
> +                       u32 gen7_latched_oastatus1;
> +
> +                       struct i915_oa_ops ops;
> +                       const struct i915_oa_format *oa_formats;
> +                       int n_builtin_sets;
>                 } oa;
>         } perf;
>
> @@ -3499,6 +3546,9 @@ struct drm_i915_gem_object *
>  i915_gem_alloc_context_obj(struct drm_device *dev, size_t size);
>  struct i915_gem_context *
>  i915_gem_context_create_gvt(struct drm_device *dev);
> +int i915_gem_context_pin_legacy_rcs_state(struct drm_i915_private *dev_priv,
> +                                         struct i915_gem_context *ctx,
> +                                         u64 flags);
>
>  static inline struct i915_gem_context *
>  i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
> @@ -3545,6 +3595,8 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev, void *data,
>
>  int i915_perf_open_ioctl(struct drm_device *dev, void *data,
>                          struct drm_file *file);
> +void i915_oa_legacy_context_pin_notify(struct drm_i915_private *dev_priv,
> +                                      struct i915_gem_context *ctx);
>
>  /* i915_gem_evict.c */
>  int __must_check i915_gem_evict_something(struct i915_address_space *vm,
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index df10f4e9..62966e9 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -134,6 +134,25 @@ static int get_context_size(struct drm_i915_private *dev_priv)
>         return ret;
>  }
>
> +int i915_gem_context_pin_legacy_rcs_state(struct drm_i915_private *dev_priv,
> +                                         struct i915_gem_context *ctx,
> +                                         u64 flags)
> +{
> +       int ret;
> +
> +       lockdep_assert_held(&ctx->i915->drm.struct_mutex);
> +
> +       ret = i915_vma_pin(ctx->engine[RCS].state, 0,
> +                          ctx->ggtt_alignment,
> +                          flags);
> +       if (ret)
> +               return ret;
> +
> +       i915_oa_legacy_context_pin_notify(dev_priv, ctx);
> +
> +       return 0;
> +}
> +
>  void i915_gem_context_free(struct kref *ctx_ref)
>  {
>         struct i915_gem_context *ctx = container_of(ctx_ref, typeof(*ctx), ref);
> @@ -770,7 +789,8 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
>         }
>
>         /* Trying to pin first makes error handling easier. */
> -       ret = i915_vma_pin(vma, 0, to->ggtt_alignment, PIN_GLOBAL);
> +       ret = i915_gem_context_pin_legacy_rcs_state(engine->i915, to,
> +                                                   PIN_GLOBAL);
>         if (ret)
>                 return ret;
>
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 87530f5..5305982 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -28,14 +28,860 @@
>  #include <linux/sizes.h>
>
>  #include "i915_drv.h"
> +#include "intel_ringbuffer.h"
> +#include "intel_lrc.h"
Superfluous includes.

> +#include "i915_oa_hsw.h"
> +
> +/* Must be a power of two */
> +#define OA_BUFFER_SIZE         SZ_16M
It's a power of two between 128K and 16M, maybe add a build_bug_on and
build_bug_on_not_power_of_2 to check this?

> +#define OA_TAKEN(tail, head)   ((tail - head) & (OA_BUFFER_SIZE - 1))
> +
> +/* There's a HW race condition between OA unit tail pointer register updates and
> + * writes to memory whereby the tail pointer can sometimes get ahead of what's
> + * been written out to the OA buffer so far.
> + *
> + * Although this can be observed explicitly by checking for a zeroed report-id
> + * field in tail reports, it seems preferable to account for this earlier e.g.
> + * as part of the _oa_buffer_is_empty checks to minimize -EAGAIN polling cycles
> + * in this situation.
> + *
> + * To give time for the most recent reports to land before they may be copied to
> + * userspace, the driver operates as if the tail pointer effectively lags behind
> + * the HW tail pointer by 'tail_margin' bytes. The margin in bytes is calculated
> + * based on this constant in nanoseconds, the current OA sampling exponent
> + * and current report size.
> + *
> + * There is also a fallback check while reading to simply skip over reports with
> + * a zeroed report-id.
> + */
> +#define OA_TAIL_MARGIN_NSEC    100000ULL
Yikes!

> +
> +/* frequency for checking whether the OA unit has written new reports to the
> + * circular OA buffer...
> + */
> +#define POLL_FREQUENCY 200
> +#define POLL_PERIOD (NSEC_PER_SEC / POLL_FREQUENCY)
> +
> +/* The maximum exponent the hardware accepts is 63 (essentially it selects one
> + * of the 64bit timestamp bits to trigger reports from) but there's currently
> + * no known use case for sampling as infrequently as once per 47 thousand years.
> + *
> + * Since the timestamps included in OA reports are only 32bits it seems
> + * reasonable to limit the OA exponent where it's still possible to account for
> + * overflow in OA report timestamps.
> + */
> +#define OA_EXPONENT_MAX 31
> +
> +/* XXX: beware if future OA HW adds new report formats that the current
> + * code assumes all reports have a power-of-two size and ~(size - 1) can
> + * be used as a mask to align the OA tail pointer.
> + */
> +static struct i915_oa_format hsw_oa_formats[I915_OA_FORMAT_MAX] = {
> +       [I915_OA_FORMAT_A13]        = { 0, 64 },
> +       [I915_OA_FORMAT_A29]        = { 1, 128 },
> +       [I915_OA_FORMAT_A13_B8_C8]  = { 2, 128 },
> +       /* A29_B8_C8 Disallowed as 192 bytes doesn't factor into buffer size */
> +       [I915_OA_FORMAT_B4_C8]      = { 4, 64 },
> +       [I915_OA_FORMAT_A45_B8_C8]  = { 5, 256 },
> +       [I915_OA_FORMAT_B4_C8_A16]  = { 6, 128 },
> +       [I915_OA_FORMAT_C4_B8]      = { 7, 64 },
> +};
> +
> +#define SAMPLE_OA_REPORT      (1<<0)
>
>  struct perf_open_properties {
>         u32 sample_flags;
>
>         u64 single_context:1;
>         u64 ctx_handle;
> +
> +       /* OA sampling state */
> +       int metrics_set;
> +       int oa_format;
> +       bool oa_periodic;
> +       int oa_period_exponent;
>  };
>
> +/* NB: This is either called via fops or the poll check hrtimer (atomic ctx)
> + *
> + * It's safe to read OA config state here unlocked, assuming that this is only
> + * called while the stream is enabled, while the global OA configuration can't
> + * be modified.
> + *
> + * Note: we don't lock around the head/tail reads even though there's the slim
> + * possibility of read() fop errors forcing a re-init of the OA buffer
> + * pointers.  A race here could result in a false positive !empty status which
> + * is acceptable.
> + */
> +static bool gen7_oa_buffer_is_empty_fop_unlocked(struct drm_i915_private *dev_priv)
> +{
> +       int report_size = dev_priv->perf.oa.oa_buffer.format_size;
> +       u32 oastatus2 = I915_READ(GEN7_OASTATUS2);
> +       u32 oastatus1 = I915_READ(GEN7_OASTATUS1);
> +       u32 head = oastatus2 & GEN7_OASTATUS2_HEAD_MASK;
> +       u32 tail = oastatus1 & GEN7_OASTATUS1_TAIL_MASK;
> +
> +       return OA_TAKEN(tail, head) <
> +               dev_priv->perf.oa.tail_margin + report_size;
> +}
> +
> +/**
> + * Appends a status record to a userspace read() buffer.
> + */
> +static int append_oa_status(struct i915_perf_stream *stream,
> +                           char __user *buf,
> +                           size_t count,
> +                           size_t *offset,
> +                           enum drm_i915_perf_record_type type)
> +{
> +       struct drm_i915_perf_record_header header = { type, 0, sizeof(header) };
> +
> +       if ((count - *offset) < header.size)
> +               return -ENOSPC;
> +
> +       if (copy_to_user(buf + *offset, &header, sizeof(header)))
> +               return -EFAULT;
> +
> +       (*offset) += header.size;
> +
> +       return 0;
> +}
> +
> +/**
> + * Copies single OA report into userspace read() buffer.
> + */
> +static int append_oa_sample(struct i915_perf_stream *stream,
> +                           char __user *buf,
> +                           size_t count,
> +                           size_t *offset,
> +                           const u8 *report)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +       int report_size = dev_priv->perf.oa.oa_buffer.format_size;
> +       struct drm_i915_perf_record_header header;
> +       u32 sample_flags = stream->sample_flags;
> +
> +       header.type = DRM_I915_PERF_RECORD_SAMPLE;
> +       header.pad = 0;
> +       header.size = stream->sample_size;
> +
> +       if ((count - *offset) < header.size)
> +               return -ENOSPC;
> +
> +       buf += *offset;
> +       if (copy_to_user(buf, &header, sizeof(header)))
> +               return -EFAULT;
> +       buf += sizeof(header);
> +
> +       if (sample_flags & SAMPLE_OA_REPORT) {
> +               if (copy_to_user(buf, report, report_size))
> +                       return -EFAULT;
> +       }
> +
> +       (*offset) += header.size;
> +
> +       return 0;
> +}
> +
> +/**
> + * Copies all buffered OA reports into userspace read() buffer.
> + * @head_ptr: (inout): the head pointer before and after appending
> + *
> + * Returns 0 on success, negative error code on failure.
> + *
> + * Notably any error condition resulting in a short read (-ENOSPC or
> + * -EFAULT) will be returned even though one or more records may
> + * have been successfully copied. In this case it's up to the caller
> + * to decide if the error should be squashed before returning to
> + * userspace.
> + */
> +static int gen7_append_oa_reports(struct i915_perf_stream *stream,
> +                                 char __user *buf,
> +                                 size_t count,
> +                                 size_t *offset,
> +                                 u32 *head_ptr,
> +                                 u32 tail)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +       int report_size = dev_priv->perf.oa.oa_buffer.format_size;
> +       u8 *oa_buf_base = dev_priv->perf.oa.oa_buffer.addr;
> +       int tail_margin = dev_priv->perf.oa.tail_margin;
> +       u32 mask = (OA_BUFFER_SIZE - 1);
> +       u32 head;
> +       u32 taken;
> +       int ret = 0;
> +
> +       BUG_ON(!stream->enabled);
> +
> +       head = *head_ptr - dev_priv->perf.oa.oa_buffer.gtt_offset;
> +       tail -= dev_priv->perf.oa.oa_buffer.gtt_offset;
> +
> +       /* The OA unit is expected to wrap the tail pointer according to the OA
> +        * buffer size and since we should never write a misaligned head
> +        * pointer we don't expect to read one back either...
> +        */
> +       if (tail > OA_BUFFER_SIZE || head > OA_BUFFER_SIZE ||
> +           head % report_size) {
> +               DRM_ERROR("Inconsistent OA buffer pointer (head = %u, tail = %u): force restart",
> +                         head, tail);
> +               dev_priv->perf.oa.ops.oa_disable(dev_priv);
> +               dev_priv->perf.oa.ops.oa_enable(dev_priv);
> +               *head_ptr = I915_READ(GEN7_OASTATUS2) &
> +                       GEN7_OASTATUS2_HEAD_MASK;
> +               return -EIO;
> +       }
> +
> +
> +       /* The tail pointer increases in 64 byte increments, not in report_size
> +        * steps...
> +        */
> +       tail &= ~(report_size - 1);
> +
> +       /* Move the tail pointer back by the current tail_margin to account for
> +        * the possibility that the latest reports may not have really landed
> +        * in memory yet...
> +        */
> +
> +       if (OA_TAKEN(tail, head) < report_size + tail_margin)
> +               return -EAGAIN;
> +
> +       tail -= tail_margin;
> +       tail &= mask;
> +
> +       for (/* none */;
> +            (taken = OA_TAKEN(tail, head));
> +            head = (head + report_size) & mask) {
> +               u8 *report = oa_buf_base + head;
> +               u32 *report32 = (void *)report;
> +
> +               /* All the report sizes factor neatly into the buffer
> +                * size so we never expect to see a report split
> +                * between the beginning and end of the buffer.
> +                *
> +                * Given the initial alignment check a misalignment
> +                * here would imply a driver bug that would result
> +                * in an overrun.
> +                */
> +               BUG_ON((OA_BUFFER_SIZE - head) < report_size);
> +
> +               /* The report-ID field for periodic samples includes
> +                * some undocumented flags related to what triggered
> +                * the report and is never expected to be zero so we
> +                * can check that the report isn't invalid before
> +                * copying it to userspace...
> +                */
> +               if (report32[0] == 0) {
> +                       DRM_ERROR("Skipping spurious, invalid OA report\n");
> +                       continue;
> +               }
> +
> +               ret = append_oa_sample(stream, buf, count, offset, report);
> +               if (ret)
> +                       break;
> +
> +               /* The above report-id field sanity check is based on
> +                * the assumption that the OA buffer is initially
> +                * zeroed and we reset the field after copying so the
> +                * check is still meaningful once old reports start
> +                * being overwritten.
> +                */
> +               report32[0] = 0;
> +       }
> +
> +       *head_ptr = dev_priv->perf.oa.oa_buffer.gtt_offset + head;
> +
> +       return ret;
> +}
> +
> +static int gen7_oa_read(struct i915_perf_stream *stream,
> +                       char __user *buf,
> +                       size_t count,
> +                       size_t *offset)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +       int report_size = dev_priv->perf.oa.oa_buffer.format_size;
> +       u32 oastatus2;
> +       u32 oastatus1;
> +       u32 head;
> +       u32 tail;
> +       int ret;
> +
> +       BUG_ON(!dev_priv->perf.oa.oa_buffer.addr);
> +
> +       oastatus2 = I915_READ(GEN7_OASTATUS2);
> +       oastatus1 = I915_READ(GEN7_OASTATUS1);
> +
> +       head = oastatus2 & GEN7_OASTATUS2_HEAD_MASK;
> +       tail = oastatus1 & GEN7_OASTATUS1_TAIL_MASK;
> +
> +       /* XXX: On Haswell we don't have a safe way to clear oastatus1
> +        * bits while the OA unit is enabled (while the tail pointer
> +        * may be updated asynchronously) so we ignore status bits
> +        * that have already been reported to userspace.
> +        */
> +       oastatus1 &= ~dev_priv->perf.oa.gen7_latched_oastatus1;
> +
> +       /* We treat OABUFFER_OVERFLOW as a significant error:
> +        *
> +        * - The status can be interpreted to mean that the buffer is
> +        *   currently full (with a higher precedence than OA_TAKEN()
> +        *   which will start to report a near-empty buffer after an
> +        *   overflow) but it's awkward that we can't clear the status
> +        *   on Haswell, so without a reset we won't be able to catch
> +        *   the state again.
> +        *
> +        * - Since it also implies the HW has started overwriting old
> +        *   reports it may also affect our sanity checks for invalid
> +        *   reports when copying to userspace that assume new reports
> +        *   are being written to cleared memory.
> +        *
> +        * - In the future we may want to introduce a flight recorder
> +        *   mode where the driver will automatically maintain a safe
> +        *   guard band between head/tail, avoiding this overflow
> +        *   condition, but we avoid the added driver complexity for
> +        *   now.
> +        */
> +       if (unlikely(oastatus1 & GEN7_OASTATUS1_OABUFFER_OVERFLOW)) {
> +               ret = append_oa_status(stream, buf, count, offset,
> +                                      DRM_I915_PERF_RECORD_OA_BUFFER_LOST);
> +               if (ret)
> +                       return ret;
> +
> +               DRM_ERROR("OA buffer overflow: force restart");
> +
> +               dev_priv->perf.oa.ops.oa_disable(dev_priv);
> +               dev_priv->perf.oa.ops.oa_enable(dev_priv);
> +
> +               oastatus2 = I915_READ(GEN7_OASTATUS2);
> +               oastatus1 = I915_READ(GEN7_OASTATUS1);
> +
> +               head = oastatus2 & GEN7_OASTATUS2_HEAD_MASK;
> +               tail = oastatus1 & GEN7_OASTATUS1_TAIL_MASK;
> +       }
> +
> +       if (unlikely(oastatus1 & GEN7_OASTATUS1_REPORT_LOST)) {
> +               ret = append_oa_status(stream, buf, count, offset,
> +                                      DRM_I915_PERF_RECORD_OA_REPORT_LOST);
> +               if (ret)
> +                       return ret;
> +               dev_priv->perf.oa.gen7_latched_oastatus1 |=
> +                       GEN7_OASTATUS1_REPORT_LOST;
> +       }
> +
> +       ret = gen7_append_oa_reports(stream, buf, count, offset,
> +                                    &head, tail);
> +
> +       /* All the report sizes are a power of two and the
> +        * head should always be incremented by some multiple
> +        * of the report size.
> +        *
> +        * A warning here, but notably if we later read back a
> +        * misaligned pointer we will treat that as a bug since
> +        * it could lead to a buffer overrun.
> +        */
> +       WARN_ONCE(head & (report_size - 1),
> +                 "i915: Writing misaligned OA head pointer");
> +
> +       /* Note: we update the head pointer here even if an error
> +        * was returned since the error may represent a short read
> +        * where some some reports were successfully copied.
> +        */
> +       I915_WRITE(GEN7_OASTATUS2,
> +                  ((head & GEN7_OASTATUS2_HEAD_MASK) |
> +                   OA_MEM_SELECT_GGTT));
> +
> +       return ret;
> +}
> +
> +static int i915_oa_wait_unlocked(struct i915_perf_stream *stream)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +
> +       /* We would wait indefinitly if periodic sampling is not enabled */
> +       if (!dev_priv->perf.oa.periodic)
> +               return -EIO;
> +
> +       /* Note: the oa_buffer_is_empty() condition is ok to run unlocked as it
> +        * just performs mmio reads of the OA buffer head + tail pointers and
> +        * it's assumed we're handling some operation that implies the stream
> +        * can't be destroyed until completion (such as a read()) that ensures
> +        * the device + OA buffer can't disappear
> +        */
> +       return wait_event_interruptible(dev_priv->perf.oa.poll_wq,
> +                                       !dev_priv->perf.oa.ops.oa_buffer_is_empty(dev_priv));
> +}
> +
> +static void i915_oa_poll_wait(struct i915_perf_stream *stream,
> +                             struct file *file,
> +                             poll_table *wait)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +
> +       poll_wait(file, &dev_priv->perf.oa.poll_wq, wait);
> +}
> +
> +static int i915_oa_read(struct i915_perf_stream *stream,
> +                       char __user *buf,
> +                       size_t count,
> +                       size_t *offset)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +
> +       return dev_priv->perf.oa.ops.read(stream, buf, count, offset);
> +}
> +
> +static void
> +free_oa_buffer(struct drm_i915_private *i915)
> +{
> +       mutex_lock(&i915->drm.struct_mutex);
> +
> +       i915_gem_object_unpin_map(i915->perf.oa.oa_buffer.obj);
> +       __i915_vma_unpin(i915->perf.oa.oa_buffer.vma);
> +       i915_gem_object_put(i915->perf.oa.oa_buffer.obj);
> +
> +       i915->perf.oa.oa_buffer.obj = NULL;
> +       i915->perf.oa.oa_buffer.gtt_offset = 0;
> +       i915->perf.oa.oa_buffer.addr = NULL;
> +
> +       mutex_unlock(&i915->drm.struct_mutex);
> +}
> +
> +static void i915_oa_stream_destroy(struct i915_perf_stream *stream)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +
> +       BUG_ON(stream != dev_priv->perf.oa.exclusive_stream);
> +
> +       dev_priv->perf.oa.ops.disable_metric_set(dev_priv);
> +
> +       free_oa_buffer(dev_priv);
> +
> +       intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
> +       intel_runtime_pm_put(dev_priv);
> +
> +       dev_priv->perf.oa.exclusive_stream = NULL;
> +}
> +
> +static void gen7_init_oa_buffer(struct drm_i915_private *dev_priv)
> +{
> +       /* Pre-DevBDW: OABUFFER must be set with counters off,
> +        * before OASTATUS1, but after OASTATUS2
> +        */
> +       I915_WRITE(GEN7_OASTATUS2, dev_priv->perf.oa.oa_buffer.gtt_offset |
> +                  OA_MEM_SELECT_GGTT); /* head */
> +       I915_WRITE(GEN7_OABUFFER, dev_priv->perf.oa.oa_buffer.gtt_offset);
> +       I915_WRITE(GEN7_OASTATUS1, dev_priv->perf.oa.oa_buffer.gtt_offset |
> +                  OABUFFER_SIZE_16M); /* tail */
> +
> +       /* On Haswell we have to track which OASTATUS1 flags we've
> +        * already seen since they can't be cleared while periodic
> +        * sampling is enabled.
> +        */
> +       dev_priv->perf.oa.gen7_latched_oastatus1 = 0;
> +
> +       /* NB: although the OA buffer will initially be allocated
> +        * zeroed via shmfs (and so this memset is redundant when
> +        * first allocating), we may re-init the OA buffer, either
> +        * when re-enabling a stream or in error/reset paths.
> +        *
> +        * The reason we clear the buffer for each re-init is for the
> +        * sanity check in gen7_append_oa_reports() that looks at the
> +        * report-id field to make sure it's non-zero which relies on
> +        * the assumption that new reports are being written to zeroed
> +        * memory...
> +        */
> +       memset(dev_priv->perf.oa.oa_buffer.addr, 0, SZ_16M);
OA_BUFFER_SIZE

> +
> +       /* Maybe make ->pollin per-stream state if we support multiple
> +        * concurrent streams in the future. */
> +       atomic_set(&dev_priv->perf.oa.pollin, false);
> +}
> +
> +static int alloc_oa_buffer(struct drm_i915_private *dev_priv)
> +{
> +       struct drm_i915_gem_object *bo;
> +       enum i915_map_type map;
> +       struct i915_vma *vma;
> +       int ret;
> +
> +       BUG_ON(dev_priv->perf.oa.oa_buffer.obj);
> +
> +       ret = i915_mutex_lock_interruptible(&dev_priv->drm);
> +       if (ret)
> +               return ret;
> +
> +       bo = i915_gem_object_create(&dev_priv->drm, OA_BUFFER_SIZE);
> +       if (IS_ERR(bo)) {
> +               DRM_ERROR("Failed to allocate OA buffer\n");
> +               ret = PTR_ERR(bo);
> +               goto unlock;
> +       }
> +       dev_priv->perf.oa.oa_buffer.obj = bo;
> +
> +       ret = i915_gem_object_set_cache_level(bo, I915_CACHE_LLC);
> +       if (ret)
> +               goto err_unref;
> +
> +       /* PreHSW required 512K alignment, HSW requires 16M */
> +       vma = i915_gem_object_ggtt_pin(bo, NULL, 0, SZ_16M, PIN_MAPPABLE);
> +       if (IS_ERR(vma)) {
> +               ret = PTR_ERR(vma);
> +               goto err_unref;
> +       }
> +       dev_priv->perf.oa.oa_buffer.vma = vma;
> +
> +       map = HAS_LLC(dev_priv) ? I915_MAP_WB : I915_MAP_WC;
> +
> +       dev_priv->perf.oa.oa_buffer.gtt_offset = i915_ggtt_offset(vma);
> +       dev_priv->perf.oa.oa_buffer.addr = i915_gem_object_pin_map(bo, map);
> +       if (dev_priv->perf.oa.oa_buffer.addr == NULL)
i915_gem_object_pin_map can't return NULL.

> +               goto err_unpin;
> +
> +       dev_priv->perf.oa.ops.init_oa_buffer(dev_priv);
> +
> +       DRM_DEBUG_DRIVER("OA Buffer initialized, gtt offset = 0x%x, vaddr = %p",
> +                        dev_priv->perf.oa.oa_buffer.gtt_offset,
> +                        dev_priv->perf.oa.oa_buffer.addr);
> +
> +       goto unlock;
> +
> +err_unpin:
> +       __i915_vma_unpin(vma);
> +
> +err_unref:
> +       i915_gem_object_put(bo);
> +
> +       dev_priv->perf.oa.oa_buffer.gtt_offset = 0;
> +       dev_priv->perf.oa.oa_buffer.addr = NULL;
> +       dev_priv->perf.oa.oa_buffer.vma = NULL;
> +       dev_priv->perf.oa.oa_buffer.obj = NULL;
> +
> +unlock:
> +       mutex_unlock(&dev_priv->drm.struct_mutex);
> +       return ret;
> +}
> +
> +static void config_oa_regs(struct drm_i915_private *dev_priv,
> +                          const struct i915_oa_reg *regs,
> +                          int n_regs)
> +{
> +       int i;
> +
> +       for (i = 0; i < n_regs; i++) {
> +               const struct i915_oa_reg *reg = regs + i;
> +
> +               I915_WRITE(reg->addr, reg->value);
> +       }
> +}
> +
> +static int hsw_enable_metric_set(struct drm_i915_private *dev_priv)
> +{
> +       int ret = i915_oa_select_metric_set_hsw(dev_priv);
> +
> +       if (ret)
> +               return ret;
> +
> +       I915_WRITE(GDT_CHICKEN_BITS, (I915_READ(GDT_CHICKEN_BITS) |
> +                                     GT_NOA_ENABLE));
> +
> +       /* PRM:
> +        *
> +        * OA unit is using “crclk” for its functionality. When trunk
> +        * level clock gating takes place, OA clock would be gated,
> +        * unable to count the events from non-render clock domain.
> +        * Render clock gating must be disabled when OA is enabled to
> +        * count the events from non-render domain. Unit level clock
> +        * gating for RCS should also be disabled.
> +        */
> +       I915_WRITE(GEN7_MISCCPCTL, (I915_READ(GEN7_MISCCPCTL) &
> +                                   ~GEN7_DOP_CLOCK_GATE_ENABLE));
> +       I915_WRITE(GEN6_UCGCTL1, (I915_READ(GEN6_UCGCTL1) |
> +                                 GEN6_CSUNIT_CLOCK_GATE_DISABLE));
> +
> +       config_oa_regs(dev_priv, dev_priv->perf.oa.mux_regs,
> +                      dev_priv->perf.oa.mux_regs_len);
> +
> +       /* It apparently takes a fairly long time for a new MUX
> +        * configuration to be be applied after these register writes.
> +        * This delay duration was derived empirically based on the
> +        * render_basic config but hopefully it covers the maximum
> +        * configuration latency.
> +        *
> +        * As a fallback, the checks in _append_oa_reports() to skip
> +        * invalid OA reports do also seem to work to discard reports
> +        * generated before this config has completed - albeit not
> +        * silently.
> +        *
> +        * Unfortunately this is essentially a magic number, since we
> +        * don't currently know of a reliable mechanism for predicting
> +        * how long the MUX config will take to apply and besides
> +        * seeing invalid reports we don't know of a reliable way to
> +        * explicitly check that the MUX config has landed.
> +        *
> +        * It's even possible we've miss characterized the underlying
> +        * problem - it just seems like the simplest explanation why
> +        * a delay at this location would mitigate any invalid reports.
> +        */
> +       usleep_range(15000, 20000);
> +
> +       config_oa_regs(dev_priv, dev_priv->perf.oa.b_counter_regs,
> +                      dev_priv->perf.oa.b_counter_regs_len);
> +
> +       return 0;
> +}
> +
> +static void hsw_disable_metric_set(struct drm_i915_private *dev_priv)
> +{
> +       I915_WRITE(GEN6_UCGCTL1, (I915_READ(GEN6_UCGCTL1) &
> +                                 ~GEN6_CSUNIT_CLOCK_GATE_DISABLE));
> +       I915_WRITE(GEN7_MISCCPCTL, (I915_READ(GEN7_MISCCPCTL) |
> +                                   GEN7_DOP_CLOCK_GATE_ENABLE));
> +
> +       I915_WRITE(GDT_CHICKEN_BITS, (I915_READ(GDT_CHICKEN_BITS) &
> +                                     ~GT_NOA_ENABLE));
> +}
> +
> +static void gen7_update_oacontrol_locked(struct drm_i915_private *dev_priv)
> +{
> +       assert_spin_locked(&dev_priv->perf.hook_lock);
> +
> +       if (dev_priv->perf.oa.exclusive_stream->enabled) {
> +               unsigned long ctx_id = 0;
> +
> +               if (dev_priv->perf.oa.exclusive_stream->ctx)
> +                       ctx_id = dev_priv->perf.oa.specific_ctx_id;
> +
> +               if (dev_priv->perf.oa.exclusive_stream->ctx == NULL || ctx_id) {
gem context state pinned at ggtt offset zero is unlikely but still
possible, as pointed
out by Chris.

> +                       bool periodic = dev_priv->perf.oa.periodic;
> +                       u32 period_exponent = dev_priv->perf.oa.period_exponent;
> +                       u32 report_format = dev_priv->perf.oa.oa_buffer.format;
> +
> +                       I915_WRITE(GEN7_OACONTROL,
> +                                  (ctx_id & GEN7_OACONTROL_CTX_MASK) |
> +                                  (period_exponent <<
> +                                   GEN7_OACONTROL_TIMER_PERIOD_SHIFT) |
> +                                  (periodic ?
> +                                   GEN7_OACONTROL_TIMER_ENABLE : 0) |
> +                                  (report_format <<
> +                                   GEN7_OACONTROL_FORMAT_SHIFT) |
> +                                  (ctx_id ?
> +                                   GEN7_OACONTROL_PER_CTX_ENABLE : 0) |
> +                                  GEN7_OACONTROL_ENABLE);
> +                       return;
> +               }
> +       }
> +
> +       I915_WRITE(GEN7_OACONTROL, 0);
> +}
> +
> +static void gen7_oa_enable(struct drm_i915_private *dev_priv)
> +{
> +       unsigned long flags;
> +
> +       /* Reset buf pointers so we don't forward reports from before now.
> +        *
> +        * Think carefully if considering trying to avoid this, since it
> +        * also ensures status flags and the buffer itself are cleared
> +        * in error paths, and we have checks for invalid reports based
> +        * on the assumption that certain fields are written to zeroed
> +        * memory which this helps maintains.
> +        */
> +       gen7_init_oa_buffer(dev_priv);
> +
> +       spin_lock_irqsave(&dev_priv->perf.hook_lock, flags);
> +       gen7_update_oacontrol_locked(dev_priv);
> +       spin_unlock_irqrestore(&dev_priv->perf.hook_lock, flags);
> +}
> +
> +static void i915_oa_stream_enable(struct i915_perf_stream *stream)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +
> +       dev_priv->perf.oa.ops.oa_enable(dev_priv);
> +
> +       if (dev_priv->perf.oa.periodic)
> +               hrtimer_start(&dev_priv->perf.oa.poll_check_timer,
> +                             ns_to_ktime(POLL_PERIOD),
> +                             HRTIMER_MODE_REL_PINNED);
> +}
> +
> +static void gen7_oa_disable(struct drm_i915_private *dev_priv)
> +{
> +       I915_WRITE(GEN7_OACONTROL, 0);
> +}
> +
> +static void i915_oa_stream_disable(struct i915_perf_stream *stream)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +
> +       dev_priv->perf.oa.ops.oa_disable(dev_priv);
> +
> +       if (dev_priv->perf.oa.periodic)
> +               hrtimer_cancel(&dev_priv->perf.oa.poll_check_timer);
> +}
> +
> +static u64 oa_exponent_to_ns(struct drm_i915_private *dev_priv, int exponent)
> +{
> +       return 1000000000ULL * (2ULL << exponent) /
> +               dev_priv->perf.oa.timestamp_frequency;
> +}
> +
> +static const struct i915_perf_stream_ops i915_oa_stream_ops = {
> +       .destroy = i915_oa_stream_destroy,
> +       .enable = i915_oa_stream_enable,
> +       .disable = i915_oa_stream_disable,
> +       .wait_unlocked = i915_oa_wait_unlocked,
> +       .poll_wait = i915_oa_poll_wait,
> +       .read = i915_oa_read,
> +};
> +
> +static int i915_oa_stream_init(struct i915_perf_stream *stream,
> +                              struct drm_i915_perf_open_param *param,
> +                              struct perf_open_properties *props)
> +{
> +       struct drm_i915_private *dev_priv = stream->dev_priv;
> +       int format_size;
> +       int ret;
> +
> +       if (!(props->sample_flags & SAMPLE_OA_REPORT)) {
> +               DRM_ERROR("Only OA report sampling supported\n");
> +               return -EINVAL;
> +       }
> +
> +       if (!dev_priv->perf.oa.ops.init_oa_buffer) {
> +               DRM_ERROR("OA unit not supported\n");
> +               return -ENODEV;
> +       }
> +
> +       /* To avoid the complexity of having to accurately filter
> +        * counter reports and marshal to the appropriate client
> +        * we currently only allow exclusive access
> +        */
> +       if (dev_priv->perf.oa.exclusive_stream) {
> +               DRM_ERROR("OA unit already in use\n");
> +               return -EBUSY;
> +       }
> +
> +       if (!props->metrics_set) {
> +               DRM_ERROR("OA metric set not specified\n");
> +               return -EINVAL;
> +       }
> +
> +       if (!props->oa_format) {
> +               DRM_ERROR("OA report format not specified\n");
> +               return -EINVAL;
> +       }
> +
> +       stream->sample_size = sizeof(struct drm_i915_perf_record_header);
> +
> +       format_size = dev_priv->perf.oa.oa_formats[props->oa_format].size;
> +
> +       stream->sample_flags |= SAMPLE_OA_REPORT;
> +       stream->sample_size += format_size;
> +
> +       dev_priv->perf.oa.oa_buffer.format_size = format_size;
> +       BUG_ON(dev_priv->perf.oa.oa_buffer.format_size == 0);
> +
> +       dev_priv->perf.oa.oa_buffer.format =
> +               dev_priv->perf.oa.oa_formats[props->oa_format].format;
> +
> +       dev_priv->perf.oa.metrics_set = props->metrics_set;
> +
> +       dev_priv->perf.oa.periodic = props->oa_periodic;
> +       if (dev_priv->perf.oa.periodic) {
> +               u64 period_ns = oa_exponent_to_ns(dev_priv,
> +                                                 props->oa_period_exponent);
> +
> +               dev_priv->perf.oa.period_exponent = props->oa_period_exponent;
> +
> +               /* See comment for OA_TAIL_MARGIN_NSEC for details
> +                * about this tail_margin...
> +                */
> +               dev_priv->perf.oa.tail_margin =
> +                       ((OA_TAIL_MARGIN_NSEC / period_ns) + 1) * format_size;
> +       }
> +
> +       ret = alloc_oa_buffer(dev_priv);
> +       if (ret)
> +               return ret;
> +
> +       /* PRM - observability performance counters:
> +        *
> +        *   OACONTROL, performance counter enable, note:
> +        *
> +        *   "When this bit is set, in order to have coherent counts,
> +        *   RC6 power state and trunk clock gating must be disabled.
> +        *   This can be achieved by programming MMIO registers as
> +        *   0xA094=0 and 0xA090[31]=1"
> +        *
> +        *   In our case we are expecting that taking pm + FORCEWAKE
> +        *   references will effectively disable RC6.
> +        */
> +       intel_runtime_pm_get(dev_priv);
> +       intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
> +
> +       ret = dev_priv->perf.oa.ops.enable_metric_set(dev_priv);
> +       if (ret) {
> +               intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
> +               intel_runtime_pm_put(dev_priv);
> +               free_oa_buffer(dev_priv);
> +               return ret;
> +       }
> +
> +       stream->ops = &i915_oa_stream_ops;
> +
> +       /* On Haswell we have to track which OASTATUS1 flags we've already
> +        * seen since they can't be cleared while periodic sampling is enabled.
> +        */
> +       dev_priv->perf.oa.gen7_latched_oastatus1 = 0;
We already did this step.

> +
> +       dev_priv->perf.oa.exclusive_stream = stream;
> +
> +       return 0;
> +}
> +
> +static void gen7_update_hw_ctx_id_locked(struct drm_i915_private *dev_priv,
> +                                        u32 ctx_id)
> +{
> +       assert_spin_locked(&dev_priv->perf.hook_lock);
> +
> +       dev_priv->perf.oa.specific_ctx_id = ctx_id;
> +       gen7_update_oacontrol_locked(dev_priv);
> +}
> +
> +static void
> +i915_oa_legacy_context_pin_notify_locked(struct drm_i915_private *dev_priv,
> +                                        struct i915_gem_context *ctx)
> +{
> +       assert_spin_locked(&dev_priv->perf.hook_lock);
> +
> +       BUG_ON(i915.enable_execlists);
> +
> +       if (dev_priv->perf.oa.ops.update_hw_ctx_id_locked == NULL)
For consistency, if (!dev_priv->perf.oa.ops.update_hw_ctx_id_locked)

> +               return;
> +
> +       if (dev_priv->perf.oa.exclusive_stream &&
> +           dev_priv->perf.oa.exclusive_stream->ctx == ctx) {
> +               struct i915_vma *vma = ctx->engine[RCS].state;
> +               u32 ctx_id = i915_ggtt_offset(vma);
> +
> +               dev_priv->perf.oa.ops.update_hw_ctx_id_locked(dev_priv, ctx_id);
> +       }
> +}
> +
> +void i915_oa_legacy_context_pin_notify(struct drm_i915_private *dev_priv,
> +                                      struct i915_gem_context *ctx)
> +{
> +       unsigned long flags;
> +
> +       if (!dev_priv->perf.initialized)
> +               return;
> +
> +       spin_lock_irqsave(&dev_priv->perf.hook_lock, flags);
> +       i915_oa_legacy_context_pin_notify_locked(dev_priv, ctx);
> +       spin_unlock_irqrestore(&dev_priv->perf.hook_lock, flags);
> +}
> +
>  static ssize_t i915_perf_read_locked(struct i915_perf_stream *stream,
>                                      struct file *file,
>                                      char __user *buf,
> @@ -79,8 +925,20 @@ static ssize_t i915_perf_read(struct file *file,
>         struct drm_i915_private *dev_priv = stream->dev_priv;
>         ssize_t ret;
>
> +       /* To ensure it's handled consistently we simply treat all reads of a
> +        * disabled stream as an error. In particular it might otherwise lead
> +        * to a deadlock for blocking file descriptors...
> +        */
> +       if (!stream->enabled)
> +               return -EIO;
> +
>         if (!(file->f_flags & O_NONBLOCK)) {
> -               /* Allow false positives from stream->ops->wait_unlocked.
> +               /* There's the small chance of false positives from
> +                * stream->ops->wait_unlocked.
> +                *
> +                * E.g. with single context filtering since we only wait until
> +                * oabuffer has >= 1 report we don't immediately know whether
> +                * any reports really belong to the current context
>                  */
>                 do {
>                         ret = stream->ops->wait_unlocked(stream);
> @@ -98,21 +956,50 @@ static ssize_t i915_perf_read(struct file *file,
>                 mutex_unlock(&dev_priv->perf.lock);
>         }
>
> +       if (ret >= 0) {
> +               /* Maybe make ->pollin per-stream state if we support multiple
> +                * concurrent streams in the future. */
> +               atomic_set(&dev_priv->perf.oa.pollin, false);
> +       }
> +
>         return ret;
>  }
>
> -static unsigned int i915_perf_poll_locked(struct i915_perf_stream *stream,
> +static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer)
> +{
> +       struct drm_i915_private *dev_priv =
> +               container_of(hrtimer, typeof(*dev_priv),
> +                            perf.oa.poll_check_timer);
> +
> +       if (!dev_priv->perf.oa.ops.oa_buffer_is_empty(dev_priv)) {
> +               atomic_set(&dev_priv->perf.oa.pollin, true);
> +               wake_up(&dev_priv->perf.oa.poll_wq);
> +       }
> +
> +       hrtimer_forward_now(hrtimer, ns_to_ktime(POLL_PERIOD));
> +
> +       return HRTIMER_RESTART;
> +}
> +
> +static unsigned int i915_perf_poll_locked(struct drm_i915_private *dev_priv,
> +                                         struct i915_perf_stream *stream,
>                                           struct file *file,
>                                           poll_table *wait)
>  {
> -       unsigned int streams = 0;
> +       unsigned int events = 0;
>
>         stream->ops->poll_wait(stream, file, wait);
>
> -       if (stream->ops->can_read(stream))
> -               streams |= POLLIN;
> +       /* Note: we don't explicitly check whether there's something to read
> +        * here since this path may be very hot depending on what else
> +        * userspace is polling, or on the timeout in use. We rely solely on
> +        * the hrtimer/oa_poll_check_timer_cb to notify us when there are
> +        * samples to read.
> +        */
> +       if (atomic_read(&dev_priv->perf.oa.pollin))
> +               events |= POLLIN;
>
> -       return streams;
> +       return events;
>  }
>
>  static unsigned int i915_perf_poll(struct file *file, poll_table *wait)
> @@ -122,7 +1009,7 @@ static unsigned int i915_perf_poll(struct file *file, poll_table *wait)
>         int ret;
>
>         mutex_lock(&dev_priv->perf.lock);
> -       ret = i915_perf_poll_locked(stream, file, wait);
> +       ret = i915_perf_poll_locked(dev_priv, stream, file, wait);
>         mutex_unlock(&dev_priv->perf.lock);
>
>         return ret;
> @@ -286,18 +1173,18 @@ int i915_perf_open_ioctl_locked(struct drm_device *dev,
>                 goto err_ctx;
>         }
>
> -       stream->sample_flags = props->sample_flags;
>         stream->dev_priv = dev_priv;
>         stream->ctx = specific_ctx;
>
> -       /*
> -        * TODO: support sampling something
> -        *
> -        * For now this is as far as we can go.
> +       ret = i915_oa_stream_init(stream, param, props);
> +       if (ret)
> +               goto err_alloc;
> +
> +       /* we avoid simply assigning stream->sample_flags = props->sample_flags
> +        * to have _stream_init check the combination of sample flags more
> +        * thoroughly, but still this is the expected result at this point.
>          */
> -       DRM_ERROR("Unsupported i915 perf stream configuration\n");
> -       ret = -EINVAL;
> -       goto err_alloc;
> +       BUG_ON(stream->sample_flags != props->sample_flags);
>
>         list_add(&stream->link, &dev_priv->perf.streams);
>
> @@ -382,7 +1269,56 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
>                         props->single_context = 1;
>                         props->ctx_handle = value;
>                         break;
> -
> +               case DRM_I915_PERF_PROP_SAMPLE_OA:
> +                       props->sample_flags |= SAMPLE_OA_REPORT;
> +                       break;
> +               case DRM_I915_PERF_PROP_OA_METRICS_SET:
> +                       if (value == 0 ||
> +                           value > dev_priv->perf.oa.n_builtin_sets) {
> +                               DRM_ERROR("Unknown OA metric set ID");
> +                               return -EINVAL;
> +                       }
> +                       props->metrics_set = value;
> +                       break;
> +               case DRM_I915_PERF_PROP_OA_FORMAT:
> +                       if (value == 0 || value >= I915_OA_FORMAT_MAX) {
> +                               DRM_ERROR("Invalid OA report format\n");
> +                               return -EINVAL;
> +                       }
> +                       if (!dev_priv->perf.oa.oa_formats[value].size) {
> +                               DRM_ERROR("Invalid OA report format\n");
> +                               return -EINVAL;
> +                       }
> +                       props->oa_format = value;
> +                       break;
> +               case DRM_I915_PERF_PROP_OA_EXPONENT:
> +                       if (value > OA_EXPONENT_MAX) {
> +                               DRM_ERROR("OA timer exponent too high (> %u)\n",
> +                                         OA_EXPONENT_MAX);
> +                               return -EINVAL;
> +                       }
> +
> +                       /* NB: The exponent represents a period as follows:
> +                        *
> +                        *   80ns * 2^(period_exponent + 1)
> +                        *
> +                        * Theoretically we can program the OA unit to sample
> +                        * every 160ns but don't allow that by default unless
> +                        * root.
> +                        *
> +                        * Referring to perf's
> +                        * kernel.perf_event_max_sample_rate for a precedent
> +                        * (100000 by default); with an OA exponent of 6 we get
> +                        * a period of 10.240 microseconds -just under 100000Hz
> +                        */
> +                       if (value < 6 && !capable(CAP_SYS_ADMIN)) {
> +                               DRM_ERROR("Sampling period too high without root privileges\n");
> +                               return -EACCES;
> +                       }
> +
> +                       props->oa_periodic = true;
> +                       props->oa_period_exponent = value;
> +                       break;
>                 case DRM_I915_PERF_PROP_MAX:
>                         BUG();
>                 }
> @@ -431,8 +1367,35 @@ int i915_perf_open_ioctl(struct drm_device *dev, void *data,
>
>  void i915_perf_init(struct drm_i915_private *dev_priv)
>  {
> +       if (!IS_HASWELL(dev_priv))
> +               return;
> +
> +       hrtimer_init(&dev_priv->perf.oa.poll_check_timer,
> +                    CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +       dev_priv->perf.oa.poll_check_timer.function = oa_poll_check_timer_cb;
> +       init_waitqueue_head(&dev_priv->perf.oa.poll_wq);
> +
>         INIT_LIST_HEAD(&dev_priv->perf.streams);
>         mutex_init(&dev_priv->perf.lock);
> +       spin_lock_init(&dev_priv->perf.hook_lock);
> +
> +       dev_priv->perf.oa.ops.init_oa_buffer = gen7_init_oa_buffer;
> +       dev_priv->perf.oa.ops.enable_metric_set = hsw_enable_metric_set;
> +       dev_priv->perf.oa.ops.disable_metric_set = hsw_disable_metric_set;
> +       dev_priv->perf.oa.ops.oa_enable = gen7_oa_enable;
> +       dev_priv->perf.oa.ops.oa_disable = gen7_oa_disable;
> +       dev_priv->perf.oa.ops.update_hw_ctx_id_locked =
> +               gen7_update_hw_ctx_id_locked;
> +       dev_priv->perf.oa.ops.read = gen7_oa_read;
> +       dev_priv->perf.oa.ops.oa_buffer_is_empty =
> +               gen7_oa_buffer_is_empty_fop_unlocked;
> +
> +       dev_priv->perf.oa.timestamp_frequency = 12500000;
Slightly magical.

> +
> +       dev_priv->perf.oa.oa_formats = hsw_oa_formats;
> +
> +       dev_priv->perf.oa.n_builtin_sets =
> +               i915_oa_n_builtin_metric_sets_hsw;
>
>         dev_priv->perf.initialized = true;
>  }
> @@ -442,7 +1405,6 @@ void i915_perf_fini(struct drm_i915_private *dev_priv)
>         if (!dev_priv->perf.initialized)
>                 return;
>
> -       /* Currently nothing to clean up */
> -
> +       memset(&dev_priv->perf.oa.ops, 0, sizeof(dev_priv->perf.oa.ops));
>         dev_priv->perf.initialized = false;
>  }
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 90756b2..a0ccc09 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -617,6 +617,343 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
>  #define HSW_CS_GPR_UDW(n)               _MMIO(0x2600 + (n) * 8 + 4)
>
>  #define GEN7_OACONTROL _MMIO(0x2360)
> +#define  GEN7_OACONTROL_CTX_MASK           0xFFFFF000
> +#define  GEN7_OACONTROL_TIMER_PERIOD_MASK   0x3F
> +#define  GEN7_OACONTROL_TIMER_PERIOD_SHIFT  6
> +#define  GEN7_OACONTROL_TIMER_ENABLE       (1<<5)
> +#define  GEN7_OACONTROL_FORMAT_A13         (0<<2)
> +#define  GEN7_OACONTROL_FORMAT_A29         (1<<2)
> +#define  GEN7_OACONTROL_FORMAT_A13_B8_C8    (2<<2)
> +#define  GEN7_OACONTROL_FORMAT_A29_B8_C8    (3<<2)
> +#define  GEN7_OACONTROL_FORMAT_B4_C8       (4<<2)
> +#define  GEN7_OACONTROL_FORMAT_A45_B8_C8    (5<<2)
> +#define  GEN7_OACONTROL_FORMAT_B4_C8_A16    (6<<2)
> +#define  GEN7_OACONTROL_FORMAT_C4_B8       (7<<2)
> +#define  GEN7_OACONTROL_FORMAT_SHIFT       2
> +#define  GEN7_OACONTROL_PER_CTX_ENABLE     (1<<1)
> +#define  GEN7_OACONTROL_ENABLE             (1<<0)
> +
> +#define GEN8_OACTXID _MMIO(0x2364)
> +
> +#define GEN8_OACONTROL _MMIO(0x2B00)
> +#define  GEN8_OA_REPORT_FORMAT_A12         (0<<2)
> +#define  GEN8_OA_REPORT_FORMAT_A12_B8_C8    (2<<2)
> +#define  GEN8_OA_REPORT_FORMAT_A36_B8_C8    (5<<2)
> +#define  GEN8_OA_REPORT_FORMAT_C4_B8       (7<<2)
> +#define  GEN8_OA_REPORT_FORMAT_SHIFT       2
> +#define  GEN8_OA_SPECIFIC_CONTEXT_ENABLE    (1<<1)
> +#define  GEN8_OA_COUNTER_ENABLE             (1<<0)
> +
> +#define GEN8_OACTXCONTROL _MMIO(0x2360)
> +#define  GEN8_OA_TIMER_PERIOD_MASK         0x3F
> +#define  GEN8_OA_TIMER_PERIOD_SHIFT        2
> +#define  GEN8_OA_TIMER_ENABLE              (1<<1)
> +#define  GEN8_OA_COUNTER_RESUME                    (1<<0)
> +
> +#define GEN7_OABUFFER _MMIO(0x23B0) /* R/W */
> +#define  GEN7_OABUFFER_OVERRUN_DISABLE     (1<<3)
> +#define  GEN7_OABUFFER_EDGE_TRIGGER        (1<<2)
> +#define  GEN7_OABUFFER_STOP_RESUME_ENABLE   (1<<1)
> +#define  GEN7_OABUFFER_RESUME              (1<<0)
> +
> +#define GEN8_OABUFFER _MMIO(0x2b14)
> +
> +#define GEN7_OASTATUS1 _MMIO(0x2364)
> +#define  GEN7_OASTATUS1_TAIL_MASK          0xffffffc0
> +#define  GEN7_OASTATUS1_COUNTER_OVERFLOW    (1<<2)
> +#define  GEN7_OASTATUS1_OABUFFER_OVERFLOW   (1<<1)
> +#define  GEN7_OASTATUS1_REPORT_LOST        (1<<0)
> +
> +#define GEN7_OASTATUS2 _MMIO(0x2368)
> +#define GEN7_OASTATUS2_HEAD_MASK    0xffffffc0
> +
> +#define GEN8_OASTATUS _MMIO(0x2b08)
> +#define  GEN8_OASTATUS_OVERRUN_STATUS      (1<<3)
> +#define  GEN8_OASTATUS_COUNTER_OVERFLOW     (1<<2)
> +#define  GEN8_OASTATUS_OABUFFER_OVERFLOW    (1<<1)
> +#define  GEN8_OASTATUS_REPORT_LOST         (1<<0)
> +
> +#define GEN8_OAHEADPTR _MMIO(0x2B0C)
> +#define GEN8_OATAILPTR _MMIO(0x2B10)
> +
> +#define OABUFFER_SIZE_128K  (0<<3)
> +#define OABUFFER_SIZE_256K  (1<<3)
> +#define OABUFFER_SIZE_512K  (2<<3)
> +#define OABUFFER_SIZE_1M    (3<<3)
> +#define OABUFFER_SIZE_2M    (4<<3)
> +#define OABUFFER_SIZE_4M    (5<<3)
> +#define OABUFFER_SIZE_8M    (6<<3)
> +#define OABUFFER_SIZE_16M   (7<<3)
> +
> +#define OA_MEM_SELECT_GGTT  (1<<0)
> +
> +#define EU_PERF_CNTL0      _MMIO(0xe458)
> +
> +#define GDT_CHICKEN_BITS    _MMIO(0x9840)
> +#define GT_NOA_ENABLE      0x00000080
> +
> +/*
> + * OA Boolean state
> + */
> +
> +#define OAREPORTTRIG1 _MMIO(0x2740)
> +#define OAREPORTTRIG1_THRESHOLD_MASK 0xffff
> +#define OAREPORTTRIG1_EDGE_LEVEL_TRIGER_SELECT_MASK 0xffff0000 /* 0=level */
> +
> +#define OAREPORTTRIG2 _MMIO(0x2744)
> +#define OAREPORTTRIG2_INVERT_A_0  (1<<0)
> +#define OAREPORTTRIG2_INVERT_A_1  (1<<1)
> +#define OAREPORTTRIG2_INVERT_A_2  (1<<2)
> +#define OAREPORTTRIG2_INVERT_A_3  (1<<3)
> +#define OAREPORTTRIG2_INVERT_A_4  (1<<4)
> +#define OAREPORTTRIG2_INVERT_A_5  (1<<5)
> +#define OAREPORTTRIG2_INVERT_A_6  (1<<6)
> +#define OAREPORTTRIG2_INVERT_A_7  (1<<7)
> +#define OAREPORTTRIG2_INVERT_A_8  (1<<8)
> +#define OAREPORTTRIG2_INVERT_A_9  (1<<9)
> +#define OAREPORTTRIG2_INVERT_A_10 (1<<10)
> +#define OAREPORTTRIG2_INVERT_A_11 (1<<11)
> +#define OAREPORTTRIG2_INVERT_A_12 (1<<12)
> +#define OAREPORTTRIG2_INVERT_A_13 (1<<13)
> +#define OAREPORTTRIG2_INVERT_A_14 (1<<14)
> +#define OAREPORTTRIG2_INVERT_A_15 (1<<15)
> +#define OAREPORTTRIG2_INVERT_B_0  (1<<16)
> +#define OAREPORTTRIG2_INVERT_B_1  (1<<17)
> +#define OAREPORTTRIG2_INVERT_B_2  (1<<18)
> +#define OAREPORTTRIG2_INVERT_B_3  (1<<19)
> +#define OAREPORTTRIG2_INVERT_C_0  (1<<20)
> +#define OAREPORTTRIG2_INVERT_C_1  (1<<21)
> +#define OAREPORTTRIG2_INVERT_D_0  (1<<22)
> +#define OAREPORTTRIG2_THRESHOLD_ENABLE     (1<<23)
> +#define OAREPORTTRIG2_REPORT_TRIGGER_ENABLE (1<<31)
> +
> +#define OAREPORTTRIG3 _MMIO(0x2748)
> +#define OAREPORTTRIG3_NOA_SELECT_MASK      0xf
> +#define OAREPORTTRIG3_NOA_SELECT_8_SHIFT    0
> +#define OAREPORTTRIG3_NOA_SELECT_9_SHIFT    4
> +#define OAREPORTTRIG3_NOA_SELECT_10_SHIFT   8
> +#define OAREPORTTRIG3_NOA_SELECT_11_SHIFT   12
> +#define OAREPORTTRIG3_NOA_SELECT_12_SHIFT   16
> +#define OAREPORTTRIG3_NOA_SELECT_13_SHIFT   20
> +#define OAREPORTTRIG3_NOA_SELECT_14_SHIFT   24
> +#define OAREPORTTRIG3_NOA_SELECT_15_SHIFT   28
> +
> +#define OAREPORTTRIG4 _MMIO(0x274c)
> +#define OAREPORTTRIG4_NOA_SELECT_MASK      0xf
> +#define OAREPORTTRIG4_NOA_SELECT_0_SHIFT    0
> +#define OAREPORTTRIG4_NOA_SELECT_1_SHIFT    4
> +#define OAREPORTTRIG4_NOA_SELECT_2_SHIFT    8
> +#define OAREPORTTRIG4_NOA_SELECT_3_SHIFT    12
> +#define OAREPORTTRIG4_NOA_SELECT_4_SHIFT    16
> +#define OAREPORTTRIG4_NOA_SELECT_5_SHIFT    20
> +#define OAREPORTTRIG4_NOA_SELECT_6_SHIFT    24
> +#define OAREPORTTRIG4_NOA_SELECT_7_SHIFT    28
> +
> +#define OAREPORTTRIG5 _MMIO(0x2750)
> +#define OAREPORTTRIG5_THRESHOLD_MASK 0xffff
> +#define OAREPORTTRIG5_EDGE_LEVEL_TRIGER_SELECT_MASK 0xffff0000 /* 0=level */
> +
> +#define OAREPORTTRIG6 _MMIO(0x2754)
> +#define OAREPORTTRIG6_INVERT_A_0  (1<<0)
> +#define OAREPORTTRIG6_INVERT_A_1  (1<<1)
> +#define OAREPORTTRIG6_INVERT_A_2  (1<<2)
> +#define OAREPORTTRIG6_INVERT_A_3  (1<<3)
> +#define OAREPORTTRIG6_INVERT_A_4  (1<<4)
> +#define OAREPORTTRIG6_INVERT_A_5  (1<<5)
> +#define OAREPORTTRIG6_INVERT_A_6  (1<<6)
> +#define OAREPORTTRIG6_INVERT_A_7  (1<<7)
> +#define OAREPORTTRIG6_INVERT_A_8  (1<<8)
> +#define OAREPORTTRIG6_INVERT_A_9  (1<<9)
> +#define OAREPORTTRIG6_INVERT_A_10 (1<<10)
> +#define OAREPORTTRIG6_INVERT_A_11 (1<<11)
> +#define OAREPORTTRIG6_INVERT_A_12 (1<<12)
> +#define OAREPORTTRIG6_INVERT_A_13 (1<<13)
> +#define OAREPORTTRIG6_INVERT_A_14 (1<<14)
> +#define OAREPORTTRIG6_INVERT_A_15 (1<<15)
> +#define OAREPORTTRIG6_INVERT_B_0  (1<<16)
> +#define OAREPORTTRIG6_INVERT_B_1  (1<<17)
> +#define OAREPORTTRIG6_INVERT_B_2  (1<<18)
> +#define OAREPORTTRIG6_INVERT_B_3  (1<<19)
> +#define OAREPORTTRIG6_INVERT_C_0  (1<<20)
> +#define OAREPORTTRIG6_INVERT_C_1  (1<<21)
> +#define OAREPORTTRIG6_INVERT_D_0  (1<<22)
> +#define OAREPORTTRIG6_THRESHOLD_ENABLE     (1<<23)
> +#define OAREPORTTRIG6_REPORT_TRIGGER_ENABLE (1<<31)
> +
> +#define OAREPORTTRIG7 _MMIO(0x2758)
> +#define OAREPORTTRIG7_NOA_SELECT_MASK      0xf
> +#define OAREPORTTRIG7_NOA_SELECT_8_SHIFT    0
> +#define OAREPORTTRIG7_NOA_SELECT_9_SHIFT    4
> +#define OAREPORTTRIG7_NOA_SELECT_10_SHIFT   8
> +#define OAREPORTTRIG7_NOA_SELECT_11_SHIFT   12
> +#define OAREPORTTRIG7_NOA_SELECT_12_SHIFT   16
> +#define OAREPORTTRIG7_NOA_SELECT_13_SHIFT   20
> +#define OAREPORTTRIG7_NOA_SELECT_14_SHIFT   24
> +#define OAREPORTTRIG7_NOA_SELECT_15_SHIFT   28
> +
> +#define OAREPORTTRIG8 _MMIO(0x275c)
> +#define OAREPORTTRIG8_NOA_SELECT_MASK      0xf
> +#define OAREPORTTRIG8_NOA_SELECT_0_SHIFT    0
> +#define OAREPORTTRIG8_NOA_SELECT_1_SHIFT    4
> +#define OAREPORTTRIG8_NOA_SELECT_2_SHIFT    8
> +#define OAREPORTTRIG8_NOA_SELECT_3_SHIFT    12
> +#define OAREPORTTRIG8_NOA_SELECT_4_SHIFT    16
> +#define OAREPORTTRIG8_NOA_SELECT_5_SHIFT    20
> +#define OAREPORTTRIG8_NOA_SELECT_6_SHIFT    24
> +#define OAREPORTTRIG8_NOA_SELECT_7_SHIFT    28
> +
> +#define OASTARTTRIG1 _MMIO(0x2710)
> +#define OASTARTTRIG1_THRESHOLD_COUNT_MASK_MBZ 0xffff0000
> +#define OASTARTTRIG1_THRESHOLD_MASK          0xffff
> +
> +#define OASTARTTRIG2 _MMIO(0x2714)
> +#define OASTARTTRIG2_INVERT_A_0 (1<<0)
> +#define OASTARTTRIG2_INVERT_A_1 (1<<1)
> +#define OASTARTTRIG2_INVERT_A_2 (1<<2)
> +#define OASTARTTRIG2_INVERT_A_3 (1<<3)
> +#define OASTARTTRIG2_INVERT_A_4 (1<<4)
> +#define OASTARTTRIG2_INVERT_A_5 (1<<5)
> +#define OASTARTTRIG2_INVERT_A_6 (1<<6)
> +#define OASTARTTRIG2_INVERT_A_7 (1<<7)
> +#define OASTARTTRIG2_INVERT_A_8 (1<<8)
> +#define OASTARTTRIG2_INVERT_A_9 (1<<9)
> +#define OASTARTTRIG2_INVERT_A_10 (1<<10)
> +#define OASTARTTRIG2_INVERT_A_11 (1<<11)
> +#define OASTARTTRIG2_INVERT_A_12 (1<<12)
> +#define OASTARTTRIG2_INVERT_A_13 (1<<13)
> +#define OASTARTTRIG2_INVERT_A_14 (1<<14)
> +#define OASTARTTRIG2_INVERT_A_15 (1<<15)
> +#define OASTARTTRIG2_INVERT_B_0 (1<<16)
> +#define OASTARTTRIG2_INVERT_B_1 (1<<17)
> +#define OASTARTTRIG2_INVERT_B_2 (1<<18)
> +#define OASTARTTRIG2_INVERT_B_3 (1<<19)
> +#define OASTARTTRIG2_INVERT_C_0 (1<<20)
> +#define OASTARTTRIG2_INVERT_C_1 (1<<21)
> +#define OASTARTTRIG2_INVERT_D_0 (1<<22)
> +#define OASTARTTRIG2_THRESHOLD_ENABLE      (1<<23)
> +#define OASTARTTRIG2_START_TRIG_FLAG_MBZ    (1<<24)
> +#define OASTARTTRIG2_EVENT_SELECT_0  (1<<28)
> +#define OASTARTTRIG2_EVENT_SELECT_1  (1<<29)
> +#define OASTARTTRIG2_EVENT_SELECT_2  (1<<30)
> +#define OASTARTTRIG2_EVENT_SELECT_3  (1<<31)
> +
> +#define OASTARTTRIG3 _MMIO(0x2718)
> +#define OASTARTTRIG3_NOA_SELECT_MASK      0xf
> +#define OASTARTTRIG3_NOA_SELECT_8_SHIFT    0
> +#define OASTARTTRIG3_NOA_SELECT_9_SHIFT    4
> +#define OASTARTTRIG3_NOA_SELECT_10_SHIFT   8
> +#define OASTARTTRIG3_NOA_SELECT_11_SHIFT   12
> +#define OASTARTTRIG3_NOA_SELECT_12_SHIFT   16
> +#define OASTARTTRIG3_NOA_SELECT_13_SHIFT   20
> +#define OASTARTTRIG3_NOA_SELECT_14_SHIFT   24
> +#define OASTARTTRIG3_NOA_SELECT_15_SHIFT   28
> +
> +#define OASTARTTRIG4 _MMIO(0x271c)
> +#define OASTARTTRIG4_NOA_SELECT_MASK       0xf
> +#define OASTARTTRIG4_NOA_SELECT_0_SHIFT    0
> +#define OASTARTTRIG4_NOA_SELECT_1_SHIFT    4
> +#define OASTARTTRIG4_NOA_SELECT_2_SHIFT    8
> +#define OASTARTTRIG4_NOA_SELECT_3_SHIFT    12
> +#define OASTARTTRIG4_NOA_SELECT_4_SHIFT    16
> +#define OASTARTTRIG4_NOA_SELECT_5_SHIFT    20
> +#define OASTARTTRIG4_NOA_SELECT_6_SHIFT    24
> +#define OASTARTTRIG4_NOA_SELECT_7_SHIFT    28
> +
> +#define OASTARTTRIG5 _MMIO(0x2720)
> +#define OASTARTTRIG5_THRESHOLD_COUNT_MASK_MBZ 0xffff0000
> +#define OASTARTTRIG5_THRESHOLD_MASK          0xffff
> +
> +#define OASTARTTRIG6 _MMIO(0x2724)
> +#define OASTARTTRIG6_INVERT_A_0 (1<<0)
> +#define OASTARTTRIG6_INVERT_A_1 (1<<1)
> +#define OASTARTTRIG6_INVERT_A_2 (1<<2)
> +#define OASTARTTRIG6_INVERT_A_3 (1<<3)
> +#define OASTARTTRIG6_INVERT_A_4 (1<<4)
> +#define OASTARTTRIG6_INVERT_A_5 (1<<5)
> +#define OASTARTTRIG6_INVERT_A_6 (1<<6)
> +#define OASTARTTRIG6_INVERT_A_7 (1<<7)
> +#define OASTARTTRIG6_INVERT_A_8 (1<<8)
> +#define OASTARTTRIG6_INVERT_A_9 (1<<9)
> +#define OASTARTTRIG6_INVERT_A_10 (1<<10)
> +#define OASTARTTRIG6_INVERT_A_11 (1<<11)
> +#define OASTARTTRIG6_INVERT_A_12 (1<<12)
> +#define OASTARTTRIG6_INVERT_A_13 (1<<13)
> +#define OASTARTTRIG6_INVERT_A_14 (1<<14)
> +#define OASTARTTRIG6_INVERT_A_15 (1<<15)
> +#define OASTARTTRIG6_INVERT_B_0 (1<<16)
> +#define OASTARTTRIG6_INVERT_B_1 (1<<17)
> +#define OASTARTTRIG6_INVERT_B_2 (1<<18)
> +#define OASTARTTRIG6_INVERT_B_3 (1<<19)
> +#define OASTARTTRIG6_INVERT_C_0 (1<<20)
> +#define OASTARTTRIG6_INVERT_C_1 (1<<21)
> +#define OASTARTTRIG6_INVERT_D_0 (1<<22)
> +#define OASTARTTRIG6_THRESHOLD_ENABLE      (1<<23)
> +#define OASTARTTRIG6_START_TRIG_FLAG_MBZ    (1<<24)
> +#define OASTARTTRIG6_EVENT_SELECT_4  (1<<28)
> +#define OASTARTTRIG6_EVENT_SELECT_5  (1<<29)
> +#define OASTARTTRIG6_EVENT_SELECT_6  (1<<30)
> +#define OASTARTTRIG6_EVENT_SELECT_7  (1<<31)
> +
> +#define OASTARTTRIG7 _MMIO(0x2728)
> +#define OASTARTTRIG7_NOA_SELECT_MASK      0xf
> +#define OASTARTTRIG7_NOA_SELECT_8_SHIFT    0
> +#define OASTARTTRIG7_NOA_SELECT_9_SHIFT    4
> +#define OASTARTTRIG7_NOA_SELECT_10_SHIFT   8
> +#define OASTARTTRIG7_NOA_SELECT_11_SHIFT   12
> +#define OASTARTTRIG7_NOA_SELECT_12_SHIFT   16
> +#define OASTARTTRIG7_NOA_SELECT_13_SHIFT   20
> +#define OASTARTTRIG7_NOA_SELECT_14_SHIFT   24
> +#define OASTARTTRIG7_NOA_SELECT_15_SHIFT   28
> +
> +#define OASTARTTRIG8 _MMIO(0x272c)
> +#define OASTARTTRIG8_NOA_SELECT_MASK      0xf
> +#define OASTARTTRIG8_NOA_SELECT_0_SHIFT    0
> +#define OASTARTTRIG8_NOA_SELECT_1_SHIFT    4
> +#define OASTARTTRIG8_NOA_SELECT_2_SHIFT    8
> +#define OASTARTTRIG8_NOA_SELECT_3_SHIFT    12
> +#define OASTARTTRIG8_NOA_SELECT_4_SHIFT    16
> +#define OASTARTTRIG8_NOA_SELECT_5_SHIFT    20
> +#define OASTARTTRIG8_NOA_SELECT_6_SHIFT    24
> +#define OASTARTTRIG8_NOA_SELECT_7_SHIFT    28
> +
> +/* CECX_0 */
> +#define OACEC_COMPARE_LESS_OR_EQUAL    6
> +#define OACEC_COMPARE_NOT_EQUAL                5
> +#define OACEC_COMPARE_LESS_THAN                4
> +#define OACEC_COMPARE_GREATER_OR_EQUAL 3
> +#define OACEC_COMPARE_EQUAL            2
> +#define OACEC_COMPARE_GREATER_THAN     1
> +#define OACEC_COMPARE_ANY_EQUAL                0
> +
> +#define OACEC_COMPARE_VALUE_MASK    0xffff
> +#define OACEC_COMPARE_VALUE_SHIFT   3
> +
> +#define OACEC_SELECT_NOA       (0<<19)
> +#define OACEC_SELECT_PREV      (1<<19)
> +#define OACEC_SELECT_BOOLEAN   (2<<19)
> +
> +/* CECX_1 */
> +#define OACEC_MASK_MASK                    0xffff
> +#define OACEC_CONSIDERATIONS_MASK   0xffff
> +#define OACEC_CONSIDERATIONS_SHIFT  16
> +
> +#define OACEC0_0 _MMIO(0x2770)
> +#define OACEC0_1 _MMIO(0x2774)
> +#define OACEC1_0 _MMIO(0x2778)
> +#define OACEC1_1 _MMIO(0x277c)
> +#define OACEC2_0 _MMIO(0x2780)
> +#define OACEC2_1 _MMIO(0x2784)
> +#define OACEC3_0 _MMIO(0x2788)
> +#define OACEC3_1 _MMIO(0x278c)
> +#define OACEC4_0 _MMIO(0x2790)
> +#define OACEC4_1 _MMIO(0x2794)
> +#define OACEC5_0 _MMIO(0x2798)
> +#define OACEC5_1 _MMIO(0x279c)
> +#define OACEC6_0 _MMIO(0x27a0)
> +#define OACEC6_1 _MMIO(0x27a4)
> +#define OACEC7_0 _MMIO(0x27a8)
> +#define OACEC7_1 _MMIO(0x27ac)
> +
>
>  #define _GEN7_PIPEA_DE_LOAD_SL 0x70068
>  #define _GEN7_PIPEB_DE_LOAD_SL 0x71068
> @@ -6977,6 +7314,7 @@ enum {
>  # define GEN6_RCCUNIT_CLOCK_GATE_DISABLE               (1 << 11)
>
>  #define GEN6_UCGCTL3                           _MMIO(0x9408)
> +# define GEN6_OACSUNIT_CLOCK_GATE_DISABLE              (1 << 20)
>
>  #define GEN7_UCGCTL4                           _MMIO(0x940c)
>  #define  GEN7_L3BANK2X_CLOCK_GATE_DISABLE      (1<<25)
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 7a74750..22d5ff1 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -2043,8 +2043,14 @@ static int intel_ring_context_pin(struct i915_gem_context *ctx,
>                 if (ret)
>                         goto error;
>
> -               ret = i915_vma_pin(ce->state, 0, ctx->ggtt_alignment,
> -                                  PIN_GLOBAL | PIN_HIGH);
> +               if (engine->id == RCS) {
> +                       u64 vma_flags = PIN_GLOBAL | PIN_HIGH;
Maybe move this up a level and reuse for both paths.

> +                       ret = i915_gem_context_pin_legacy_rcs_state(engine->i915,
> +                                                                   ctx,
> +                                                                   vma_flags);
> +               } else
> +                       ret = i915_vma_pin(ce->state, 0, ctx->ggtt_alignment,
> +                                          PIN_GLOBAL | PIN_HIGH);
>                 if (ret)
>                         goto error;
>         }
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 7777678..5ad3747 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1224,6 +1224,18 @@ struct drm_i915_gem_context_param {
>         __u64 value;
>  };
>
> +enum drm_i915_oa_format {
> +       I915_OA_FORMAT_A13 = 1,
> +       I915_OA_FORMAT_A29,
> +       I915_OA_FORMAT_A13_B8_C8,
> +       I915_OA_FORMAT_B4_C8,
> +       I915_OA_FORMAT_A45_B8_C8,
> +       I915_OA_FORMAT_B4_C8_A16,
> +       I915_OA_FORMAT_C4_B8,
> +
> +       I915_OA_FORMAT_MAX          /* non-ABI */
> +};
> +
>  enum drm_i915_perf_property_id {
>         /**
>          * Open the stream for a specific context handle (as used with
> @@ -1232,6 +1244,32 @@ enum drm_i915_perf_property_id {
>          */
>         DRM_I915_PERF_PROP_CTX_HANDLE = 1,
>
> +       /**
> +        * A value of 1 requests the inclusion of raw OA unit reports as
> +        * part of stream samples.
> +        */
> +       DRM_I915_PERF_PROP_SAMPLE_OA,
> +
> +       /**
> +        * The value specifies which set of OA unit metrics should be
> +        * be configured, defining the contents of any OA unit reports.
> +        */
> +       DRM_I915_PERF_PROP_OA_METRICS_SET,
> +
> +       /**
> +        * The value specifies the size and layout of OA unit reports.
> +        */
> +       DRM_I915_PERF_PROP_OA_FORMAT,
> +
> +       /**
> +        * Specifying this property implicitly requests periodic OA unit
> +        * sampling and (at least on Haswell) the sampling frequency is derived
> +        * from this exponent as follows:
> +        *
> +        *   80ns * 2^(period_exponent + 1)
> +        */
> +       DRM_I915_PERF_PROP_OA_EXPONENT,
> +
>         DRM_I915_PERF_PROP_MAX /* non-ABI */
>  };
>
> @@ -1251,7 +1289,22 @@ struct drm_i915_perf_open_param {
>         __u64 __user properties_ptr;
>  };
>
> +/**
> + * Enable data capture for a stream that was either opened in a disabled state
> + * via I915_PERF_FLAG_DIABLED or was later disabled via I915_PERF_IOCTL_DISABLE.
> + *
> + * It is intended to be cheaper to disable and enable a stream than it may be
> + * to close and re-open a stream with the same configuration.
> + *
> + * It's undefined whether any pending data for the stream will be lost.
> + */
>  #define I915_PERF_IOCTL_ENABLE _IO('i', 0x0)
> +
> +/**
> + * Disable data capture for a stream.
> + *
> + * It is an error to try and read a stream that is disabled.
> + */
>  #define I915_PERF_IOCTL_DISABLE        _IO('i', 0x1)
>
>  /**
> @@ -1275,17 +1328,30 @@ enum drm_i915_perf_record_type {
>          * every sample.
>          *
>          * The order of these sample properties given by userspace has no
> -        * affect on the ordering of data within a sample. The order will be
> +        * affect on the ordering of data within a sample. The order is
>          * documented here.
>          *
>          * struct {
>          *     struct drm_i915_perf_record_header header;
>          *
> -        *     TODO: itemize extensible sample data here
> +        *     { u32 oa_report[]; } && DRM_I915_PERF_PROP_SAMPLE_OA
>          * };
>          */
>         DRM_I915_PERF_RECORD_SAMPLE = 1,
>
> +       /*
> +        * Indicates that one or more OA reports were not written by the
> +        * hardware. This can happen for example if an MI_REPORT_PERF_COUNT
> +        * command collides with periodic sampling - which would be more likely
> +        * at higher sampling frequencies.
> +        */
> +       DRM_I915_PERF_RECORD_OA_REPORT_LOST = 2,
> +
> +       /**
> +        * An error occurred that resulted in all pending OA reports being lost.
> +        */
> +       DRM_I915_PERF_RECORD_OA_BUFFER_LOST = 3,
> +
>         DRM_I915_PERF_RECORD_MAX /* non-ABI */
>  };
>
> --
> 2.9.2
>
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