On Mon, 24 Jan 2022, Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx> wrote:
> All timestamps returned by GuC for GuC PMU busyness are captured from
> GUC PM TIMESTAMP. Since this timestamp does not tick when GuC goes idle,
> kmd uses RING_TIMESTAMP to measure busyness of an engine with an active
> context. In further stress testing, the MMIO read of the RING_TIMESTAMP
> is seen to cause a rare hang. Resolve the issue by using gt specific
> timestamp from PM which is in sync with the GuC PM timestamp.
>
> Fixes: 77cdd054dd2c ("drm/i915/pmu: Connect engine busyness stats from GuC to pmu")
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
> Reviewed-by: Alan Previn <alan.previn.teres.alexis@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/uc/intel_guc.h | 5 ++
> .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 56 ++++++++++++++-----
> drivers/gpu/drm/i915/i915_reg.h | 3 +-
> 3 files changed, 50 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> index d59bbf49d1c2..697d9d66acef 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> @@ -215,6 +215,11 @@ struct intel_guc {
> * context usage for overflows.
> */
> struct delayed_work work;
> +
> + /**
> + * @shift: Right shift value for the gpm timestamp
> + */
> + u32 shift;
> } timestamp;
>
> #ifdef CONFIG_DRM_I915_SELFTEST
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 1331ff91c5b0..66760f5df0c1 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1150,23 +1150,51 @@ static void guc_update_engine_gt_clks(struct intel_engine_cs *engine)
> }
> }
>
> -static void guc_update_pm_timestamp(struct intel_guc *guc,
> - struct intel_engine_cs *engine,
> - ktime_t *now)
> +static u32 gpm_timestamp_shift(struct intel_gt *gt)
> {
> - u32 gt_stamp_now, gt_stamp_hi;
> + intel_wakeref_t wakeref;
> + u32 reg, shift;
> +
> + with_intel_runtime_pm(gt->uncore->rpm, wakeref)
> + reg = intel_uncore_read(gt->uncore, RPM_CONFIG0);
> +
> + shift = (reg & GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_MASK) >>
> + GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_SHIFT;
> +
> + return 3 - shift;
> +}
> +
> +static u64 gpm_timestamp(struct intel_gt *gt)
> +{
> + u32 lo, hi, old_hi, loop = 0;
> +
> + hi = intel_uncore_read(gt->uncore, MISC_STATUS1);
> + do {
> + lo = intel_uncore_read(gt->uncore, MISC_STATUS0);
> + old_hi = hi;
> + hi = intel_uncore_read(gt->uncore, MISC_STATUS1);
> + } while (old_hi != hi && loop++ < 2);
> +
> + return ((u64)hi << 32) | lo;
> +}
See intel_uncore_read64_2x32().
> +
> +static void guc_update_pm_timestamp(struct intel_guc *guc, ktime_t *now)
> +{
> + struct intel_gt *gt = guc_to_gt(guc);
> + u32 gt_stamp_lo, gt_stamp_hi;
> + u64 gpm_ts;
>
> lockdep_assert_held(&guc->timestamp.lock);
>
> gt_stamp_hi = upper_32_bits(guc->timestamp.gt_stamp);
> - gt_stamp_now = intel_uncore_read(engine->uncore,
> - RING_TIMESTAMP(engine->mmio_base));
> + gpm_ts = gpm_timestamp(gt) >> guc->timestamp.shift;
> + gt_stamp_lo = lower_32_bits(gpm_ts);
> *now = ktime_get();
>
> - if (gt_stamp_now < lower_32_bits(guc->timestamp.gt_stamp))
> + if (gt_stamp_lo < lower_32_bits(guc->timestamp.gt_stamp))
> gt_stamp_hi++;
>
> - guc->timestamp.gt_stamp = ((u64)gt_stamp_hi << 32) | gt_stamp_now;
> + guc->timestamp.gt_stamp = ((u64)gt_stamp_hi << 32) | gt_stamp_lo;
> }
>
> /*
> @@ -1210,7 +1238,7 @@ static ktime_t guc_engine_busyness(struct intel_engine_cs *engine, ktime_t *now)
> stats_saved = *stats;
> gt_stamp_saved = guc->timestamp.gt_stamp;
> guc_update_engine_gt_clks(engine);
> - guc_update_pm_timestamp(guc, engine, now);
> + guc_update_pm_timestamp(guc, now);
> intel_gt_pm_put_async(gt);
> if (i915_reset_count(gpu_error) != reset_count) {
> *stats = stats_saved;
> @@ -1242,8 +1270,8 @@ static void __reset_guc_busyness_stats(struct intel_guc *guc)
>
> spin_lock_irqsave(&guc->timestamp.lock, flags);
>
> + guc_update_pm_timestamp(guc, &unused);
> for_each_engine(engine, gt, id) {
> - guc_update_pm_timestamp(guc, engine, &unused);
> guc_update_engine_gt_clks(engine);
> engine->stats.guc.prev_total = 0;
> }
> @@ -1260,10 +1288,11 @@ static void __update_guc_busyness_stats(struct intel_guc *guc)
> ktime_t unused;
>
> spin_lock_irqsave(&guc->timestamp.lock, flags);
> - for_each_engine(engine, gt, id) {
> - guc_update_pm_timestamp(guc, engine, &unused);
> +
> + guc_update_pm_timestamp(guc, &unused);
> + for_each_engine(engine, gt, id)
> guc_update_engine_gt_clks(engine);
> - }
> +
> spin_unlock_irqrestore(&guc->timestamp.lock, flags);
> }
>
> @@ -1757,6 +1786,7 @@ int intel_guc_submission_init(struct intel_guc *guc)
> spin_lock_init(&guc->timestamp.lock);
> INIT_DELAYED_WORK(&guc->timestamp.work, guc_timestamp_ping);
> guc->timestamp.ping_delay = (POLL_TIME_CLKS / gt->clock_frequency + 1) * HZ;
> + guc->timestamp.shift = gpm_timestamp_shift(gt);
>
> return 0;
> }
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 23b7c6930453..655517eb90ab 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1848,7 +1848,8 @@
> #define BLT_HWS_PGA_GEN7 _MMIO(0x04280)
> #define VEBOX_HWS_PGA_GEN7 _MMIO(0x04380)
>
> -#define GUCPMTIMESTAMP _MMIO(0xC3E8)
> +#define MISC_STATUS0 _MMIO(0xA500)
> +#define MISC_STATUS1 _MMIO(0xA504)
>
> #define GEN7_TLB_RD_ADDR _MMIO(0x4700)
--
Jani Nikula, Intel Open Source Graphics Center
