[Intel-gfx] [PATCH] drm/i915: Stop needlessly acquiring wakeref for debugfs/drop_caches_set

[Caz Yokoyama]

The part of i915_drop_caches_set() is
Reviewed-by: Yokoyama, Caz <caz.yokoyama at intel.com>

While I don't know whether we don't really need wakeref, calling
intel_runtime_pm_get() makes GPU active state from suspended state for
example. It makes i915_pm_rpm at gem-execbuf-stress-extra-wait test
difficult to make it faster. Thank you.
-caz

On Tue, 2019-03-12 at 15:25 +0000, Chris Wilson wrote:
> We only need to acquire a wakeref for ourselves for a few operations,
> as
> most either already acquire their own wakeref or imply a wakeref. In
> particular, it is i915_gem_set_wedged() that needed us to present it
> with a wakeref, which is incongruous with its "use anywhere" ability.
> 
> Suggested-by: Yokoyama, Caz <caz.yokoyama at intel.com>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Yokoyama, Caz <caz.yokoyama at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c | 12 ++++--------
>  drivers/gpu/drm/i915/i915_reset.c   |  4 +++-
>  2 files changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
> b/drivers/gpu/drm/i915/i915_debugfs.c
> index 6a90558de213..08683dca7775 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -3888,12 +3888,9 @@ static int
>  i915_drop_caches_set(void *data, u64 val)
>  {
>  	struct drm_i915_private *i915 = data;
> -	intel_wakeref_t wakeref;
> -	int ret = 0;
>  
>  	DRM_DEBUG("Dropping caches: 0x%08llx [0x%08llx]\n",
>  		  val, val & DROP_ALL);
> -	wakeref = intel_runtime_pm_get(i915);
>  
>  	if (val & DROP_RESET_ACTIVE &&
>  	    wait_for(intel_engines_are_idle(i915),
> I915_IDLE_ENGINES_TIMEOUT))
> @@ -3902,9 +3899,11 @@ i915_drop_caches_set(void *data, u64 val)
>  	/* No need to check and wait for gpu resets, only libdrm auto-
> restarts
>  	 * on ioctls on -EAGAIN. */
>  	if (val & (DROP_ACTIVE | DROP_RETIRE | DROP_RESET_SEQNO)) {
> +		int ret;
> +
>  		ret = mutex_lock_interruptible(&i915-
> >drm.struct_mutex);
>  		if (ret)
> -			goto out;
> +			return ret;
>  
>  		if (val & DROP_ACTIVE)
>  			ret = i915_gem_wait_for_idle(i915,
> @@ -3943,10 +3942,7 @@ i915_drop_caches_set(void *data, u64 val)
>  	if (val & DROP_FREED)
>  		i915_gem_drain_freed_objects(i915);
>  
> -out:
> -	intel_runtime_pm_put(i915, wakeref);
> -
> -	return ret;
> +	return 0;
>  }
>  
>  DEFINE_SIMPLE_ATTRIBUTE(i915_drop_caches_fops,
> diff --git a/drivers/gpu/drm/i915/i915_reset.c
> b/drivers/gpu/drm/i915/i915_reset.c
> index 3c08e08837d0..955c22b8dfc7 100644
> --- a/drivers/gpu/drm/i915/i915_reset.c
> +++ b/drivers/gpu/drm/i915/i915_reset.c
> @@ -861,9 +861,11 @@ static void __i915_gem_set_wedged(struct
> drm_i915_private *i915)
>  void i915_gem_set_wedged(struct drm_i915_private *i915)
>  {
>  	struct i915_gpu_error *error = &i915->gpu_error;
> +	intel_wakeref_t wakeref;
>  
>  	mutex_lock(&error->wedge_mutex);
> -	__i915_gem_set_wedged(i915);
> +	with_intel_runtime_pm(i915, wakeref)
> +		__i915_gem_set_wedged(i915);
>  	mutex_unlock(&error->wedge_mutex);
>  }
>