[Intel-gfx] [PATCH] drm/i915/pmu: Atomically acquire the gt_pm wakeref

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-08-01 15:21:17)
> 
> On 01/08/2019 13:20, Chris Wilson wrote:
> > Currently, we only sample if the intel_gt is awake, but we acquire our
> > own runtime_pm wakeref. Since intel_gt has transitioned to tracking its
> > own wakeref, we can atomically test and acquire that wakeref instead.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> > No automagic drop!
> > ---
> >   drivers/gpu/drm/i915/gt/intel_gt_pm.h |  8 +++++++-
> >   drivers/gpu/drm/i915/i915_pmu.c       | 23 ++++++++---------------
> >   2 files changed, 15 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > index ba960e1fc209..016298483de7 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > @@ -9,7 +9,8 @@
> >   
> >   #include <linux/types.h>
> >   
> > -struct intel_gt;
> > +#include "intel_gt_types.h"
> > +#include "intel_wakeref.h"
> >   
> >   enum {
> >       INTEL_GT_UNPARK,
> > @@ -19,6 +20,11 @@ enum {
> >   void intel_gt_pm_get(struct intel_gt *gt);
> >   void intel_gt_pm_put(struct intel_gt *gt);
> >   
> > +static inline bool intel_gt_pm_get_if_awake(struct intel_gt *gt)
> > +{
> > +     return intel_wakeref_get_if_active(&gt->wakeref);
> > +}
> > +
> >   void intel_gt_pm_init_early(struct intel_gt *gt);
> >   
> >   void intel_gt_sanitize(struct intel_gt *gt, bool force);
> > diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> > index eff86483bec0..e71192804996 100644
> > --- a/drivers/gpu/drm/i915/i915_pmu.c
> > +++ b/drivers/gpu/drm/i915/i915_pmu.c
> > @@ -8,6 +8,7 @@
> >   #include <linux/pm_runtime.h>
> >   
> >   #include "gt/intel_engine.h"
> > +#include "gt/intel_gt_pm.h"
> >   
> >   #include "i915_drv.h"
> >   #include "i915_pmu.h"
> > @@ -161,16 +162,12 @@ engines_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
> >   {
> >       struct intel_engine_cs *engine;
> >       enum intel_engine_id id;
> > -     intel_wakeref_t wakeref;
> >       unsigned long flags;
> >   
> >       if ((dev_priv->pmu.enable & ENGINE_SAMPLE_MASK) == 0)
> >               return;
> >   
> > -     wakeref = 0;
> > -     if (READ_ONCE(dev_priv->gt.awake))
> > -             wakeref = intel_runtime_pm_get_if_in_use(&dev_priv->runtime_pm);
> > -     if (!wakeref)
> > +     if (!intel_gt_pm_get_if_awake(&dev_priv->gt))
> >               return;
> >   
> >       spin_lock_irqsave(&dev_priv->uncore.lock, flags);
> > @@ -205,7 +202,7 @@ engines_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
> >       }
> >       spin_unlock_irqrestore(&dev_priv->uncore.lock, flags);
> >   
> > -     intel_runtime_pm_put(&dev_priv->runtime_pm, wakeref);
> > +     intel_gt_pm_put(&dev_priv->gt);
> >   }
> >   
> >   static void
> > @@ -222,15 +219,11 @@ frequency_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
> >               u32 val;
> >   
> >               val = dev_priv->gt_pm.rps.cur_freq;
> > -             if (dev_priv->gt.awake) {
> > -                     intel_wakeref_t wakeref;
> > -
> > -                     with_intel_runtime_pm_if_in_use(&dev_priv->runtime_pm,
> > -                                                     wakeref) {
> > -                             val = intel_uncore_read_notrace(&dev_priv->uncore,
> > -                                                             GEN6_RPSTAT1);
> > -                             val = intel_get_cagf(dev_priv, val);
> > -                     }
> > +             if (intel_gt_pm_get_if_awake(&dev_priv->gt)) {
> > +                     val = intel_uncore_read_notrace(&dev_priv->uncore,
> > +                                                     GEN6_RPSTAT1);
> > +                     val = intel_get_cagf(dev_priv, val);
> > +                     intel_gt_pm_put(&dev_priv->gt);
> >               }
> >   
> >               add_sample_mult(&dev_priv->pmu.sample[__I915_SAMPLE_FREQ_ACT],
> > 
> 
> I guess I'll be rebasing mine, at some point. :)

I anticipated you merging it at some point.

Had a thought, and we don't need gt_pm for the engine sampling, but
rather intel_engine_pm_get_if_awake.
-Chris