On Fri, 04 Mar 2022, Matt Roper <matthew.d.roper@xxxxxxxxx> wrote:
> On Fri, Mar 04, 2022 at 12:13:12PM +0200, Jani Nikula wrote:
>> On Thu, 03 Mar 2022, Matt Roper <matthew.d.roper@xxxxxxxxx> wrote:
>> > From: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
>> >
>> > Starting with DG2, preemption can no longer be controlled using userspace
>> > on a per-context basis. Instead, the hardware only allows us to enable or
>> > disable preemption in a global, system-wide basis. Also, we lose the
>> > ability to specify the preemption granularity (such as batch-level vs
>> > command-level vs object-level).
>> >
>> > As a result of this - for debugging purposes, this patch adds debugfs
>> > interface to configure (disable/enable) preemption globally.
>> >
>> > Jira: VLK-27831
>>
>> Please remove internal Jira references.
>>
>> > Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
>> > Cc: Prathap Kumar Valsan <prathap.kumar.valsan@xxxxxxxxx>
>> > Cc: John Harrison <john.c.harrison@xxxxxxxxx>
>> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
>> > Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
>> > Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
>> > ---
>> > drivers/gpu/drm/i915/gt/intel_gt_regs.h | 3 ++
>> > drivers/gpu/drm/i915/gt/intel_workarounds.c | 2 +-
>> > drivers/gpu/drm/i915/i915_debugfs.c | 50 +++++++++++++++++++++
>> > drivers/gpu/drm/i915/i915_drv.h | 3 ++
>> > 4 files changed, 57 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
>> > index 19cd34f24263..21ede1887b9f 100644
>> > --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
>> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
>> > @@ -468,6 +468,9 @@
>> > #define VF_PREEMPTION _MMIO(0x83a4)
>> > #define PREEMPTION_VERTEX_COUNT REG_GENMASK(15, 0)
>> >
>> > +#define GEN12_VFG_PREEMPTION_CHICKEN _MMIO(0x83b4)
>> > +#define GEN12_VFG_PREEMPT_CHICKEN_DISABLE REG_BIT(8)
>> > +
>> > #define GEN8_RC6_CTX_INFO _MMIO(0x8504)
>> >
>> > #define GEN12_SQCM _MMIO(0x8724)
>> > diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
>> > index c014b40d2e9f..18dc82f29776 100644
>> > --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
>> > +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
>> > @@ -2310,7 +2310,7 @@ rcs_engine_wa_init(struct intel_engine_cs *engine, struct i915_wa_list *wal)
>> > FF_DOP_CLOCK_GATE_DISABLE);
>> > }
>> >
>> > - if (IS_GRAPHICS_VER(i915, 9, 12)) {
>> > + if (HAS_PERCTX_PREEMPT_CTRL(i915)) {
>>
>> Adding HAS_PERCTX_PREEMPT_CTRL(i915) and using it is a separate change
>> from the debugfs. Please split it up.
>>
>> > /* FtrPerCtxtPreemptionGranularityControl:skl,bxt,kbl,cfl,cnl,icl,tgl */
>> > wa_masked_en(wal,
>> > GEN7_FF_SLICE_CS_CHICKEN1,
>> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
>> > index 747fe9f41e1f..40e6e17e2950 100644
>> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
>> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
>> > @@ -571,6 +571,55 @@ static int i915_wa_registers(struct seq_file *m, void *unused)
>> > return 0;
>> > }
>> >
>> > +static void i915_global_preemption_config(struct drm_i915_private *i915,
>> > + u32 val)
>> > +{
>> > + const u32 bit = GEN12_VFG_PREEMPT_CHICKEN_DISABLE;
>>
>> We rarely use const for locals, and usually only if the function is big.
>>
>> I'd probably use:
>>
>> u32 tmp = val ?
>> _MASKED_BIT_DISABLE(GEN12_VFG_PREEMPT_CHICKEN_DISABLE) :
>> _MASKED_BIT_ENABLE(GEN12_VFG_PREEMPT_CHICKEN_DISABLE);
>>
>> To have just one intel_uncore_write().
>>
>> > +
>> > + if (val)
>> > + intel_uncore_write(&i915->uncore, GEN12_VFG_PREEMPTION_CHICKEN,
>> > + _MASKED_BIT_DISABLE(bit));
>> > + else
>> > + intel_uncore_write(&i915->uncore, GEN12_VFG_PREEMPTION_CHICKEN,
>> > + _MASKED_BIT_ENABLE(bit));
>>
>> We really shouldn't be adding new direct low-level register access in
>> i915_debugfs.c.
>>
>> Please define an interface for this and add the functionality to a
>> suitable place, and then call the functions from here.
>>
>> > +}
>> > +
>> > +static int i915_global_preempt_support_get(void *data, u64 *val)
>> > +{
>> > + struct drm_i915_private *i915 = data;
>> > + intel_wakeref_t wakeref;
>> > + u32 curr_status = 0;
>> > +
>> > + if (HAS_PERCTX_PREEMPT_CTRL(i915) || GRAPHICS_VER(i915) < 11)
>> > + return -EINVAL;
>> > +
>> > + with_intel_runtime_pm(&i915->runtime_pm, wakeref)
>> > + curr_status = intel_uncore_read(&i915->uncore,
>> > + GEN12_VFG_PREEMPTION_CHICKEN);
>> > + *val = (curr_status & GEN12_VFG_PREEMPT_CHICKEN_DISABLE) ? 0 : 1;
>> > +
>> > + return 0;
>> > +}
>> > +
>> > +static int i915_global_preempt_support_set(void *data, u64 val)
>> > +{
>> > + struct drm_i915_private *i915 = data;
>> > + intel_wakeref_t wakeref;
>> > +
>> > + if (HAS_PERCTX_PREEMPT_CTRL(i915) || GRAPHICS_VER(i915) < 11)
>> > + return -EINVAL;
>> > +
>> > + with_intel_runtime_pm(&i915->runtime_pm, wakeref)
>> > + i915_global_preemption_config(i915, val);
>> > +
>> > + return 0;
>> > +}
>> > +
>> > +DEFINE_SIMPLE_ATTRIBUTE(i915_global_preempt_support_fops,
>> > + i915_global_preempt_support_get,
>> > + i915_global_preempt_support_set,
>> > + "%lld\n");
>>
>> DEFINE_DEBUGFS_ATTRIBUTE.
>
> If I'm understanding the history correctly, I think
> DEFINE_DEBUGFS_ATTRIBUTE is only supposed to be used if you're also
> using debugfs_create_file_unsafe() for registration; if you're still
> using debugfs_create_file(), then DEFINE_SIMPLE_ATTRIBUTE is preferred
> to avoid the extra overhead of redundant protection.
>
> Arguably we should shift over to debugfs_create_file_unsafe() +
> DEFINE_DEBUGFS_ATTRIBUTE, but that's probably something we should do
> driver-wide in a separate series since we're not doing that for any of
> our debugfs today.
I'll take your word for it, did not have the time to dig into it.
Thanks,
Jani.
>
> One other change we should make here is to move this into the GT debugfs
> area, rather than having it at the i915 level. I'll make that change in
> the next version.
>
>
> Matt
>
>>
>> > +
>> > static int i915_wedged_get(void *data, u64 *val)
>> > {
>> > struct drm_i915_private *i915 = data;
>> > @@ -765,6 +814,7 @@ static const struct i915_debugfs_files {
>> > const struct file_operations *fops;
>> > } i915_debugfs_files[] = {
>> > {"i915_perf_noa_delay", &i915_perf_noa_delay_fops},
>> > + {"i915_global_preempt_support", &i915_global_preempt_support_fops},
>> > {"i915_wedged", &i915_wedged_fops},
>> > {"i915_gem_drop_caches", &i915_drop_caches_fops},
>> > #if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
>> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> > index 457bc1993d19..8c3f69c87d36 100644
>> > --- a/drivers/gpu/drm/i915/i915_drv.h
>> > +++ b/drivers/gpu/drm/i915/i915_drv.h
>> > @@ -1407,6 +1407,9 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
>> > #define HAS_GUC_DEPRIVILEGE(dev_priv) \
>> > (INTEL_INFO(dev_priv)->has_guc_deprivilege)
>> >
>> > +#define HAS_PERCTX_PREEMPT_CTRL(i915) \
>> > + ((GRAPHICS_VER(i915) >= 9) && GRAPHICS_VER_FULL(i915) < IP_VER(12, 55))
>> > +
>> > static inline bool run_as_guest(void)
>> > {
>> > return !hypervisor_is_type(X86_HYPER_NATIVE);
>>
>> --
>> Jani Nikula, Intel Open Source Graphics Center
--
Jani Nikula, Intel Open Source Graphics Center
