Re: [PATCH] drm/i915/pmu: Atomically acquire the gt_pm wakeref

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> ---
> 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. :)

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

Regards,

Tvrtko
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