Re: [PATCH] drm/i915: Accurately track when we mark the hardware as idle/busy

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> We currently call intel_mark_idle() too often, as we do so as a
> side-effect of processing the request queue. However, we the calls to
> intel_mark_idle() are expected to be paired with a call to
> intel_mark_busy() (or else we try to idle the hardware by accessing
> registers that are already disabled). Make the idle/busy tracking
> explicit to prevent the multiple calls.
>
> Reported-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      |    8 ++++++++
>  drivers/gpu/drm/i915/i915_gem.c      |    4 +---
>  drivers/gpu/drm/i915/intel_display.c |   11 +++++++++++
>  drivers/gpu/drm/i915/intel_drv.h     |    2 +-
>  4 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 00222cc..8441c8a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1134,6 +1134,14 @@ struct i915_gem_mm {
>  	 */
>  	bool interruptible;
>  
> +	/**
> +	 * Is the GPU currently considered idle, or busy executing userspace
> +	 * requests?  Whilst idle, we attempt to power down the hardware and
> +	 * display clocks. In order to reduce the effect on performance, there
> +	 * is a slight delay before we do so.
> +	 */
> +	bool busy;
> +
>  	/** Bit 6 swizzling required for X tiling */
>  	uint32_t bit_6_swizzle_x;
>  	/** Bit 6 swizzling required for Y tiling */
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 9a40ef5..4525dd7 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2315,7 +2315,6 @@ int __i915_add_request(struct intel_ring_buffer *ring,
>  		i915_gem_context_reference(request->ctx);
>  
>  	request->emitted_jiffies = jiffies;
> -	was_empty = list_empty(&ring->request_list);
>  	list_add_tail(&request->list, &ring->request_list);
>  	request->file_priv = NULL;
>  
> @@ -2336,12 +2335,11 @@ int __i915_add_request(struct intel_ring_buffer *ring,
>  	if (!dev_priv->ums.mm_suspended) {
>  		i915_queue_hangcheck(ring->dev);
>  
> -		if (was_empty) {
> +		if (intel_mark_busy(dev_priv->dev)) {
>  			cancel_delayed_work_sync(&dev_priv->mm.idle_work);
>  			queue_delayed_work(dev_priv->wq,
>  					   &dev_priv->mm.retire_work,
>  					   round_jiffies_up_relative(HZ));
> -			intel_mark_busy(dev_priv->dev);
>  		}
>  	}
>  
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index e127b23..bfd6396 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -8220,8 +8220,14 @@ void intel_mark_busy(

bool intel_mark_busy(struct drm_device *dev)

-Mika

>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  
> +	if (dev_priv->mm.busy)
> +		return false;
> +
>  	hsw_package_c8_gpu_busy(dev_priv);
>  	i915_update_gfx_val(dev_priv);
> +	dev_priv->mm.busy = true;
> +
> +	return true;
>  }
>  
>  void intel_mark_idle(struct drm_device *dev)
> @@ -8229,6 +8235,11 @@ void intel_mark_idle(struct drm_device *dev)
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_crtc *crtc;
>  
> +	if (!dev_priv->mm.busy)
> +		return;
> +
> +	dev_priv->mm.busy = false;
> +
>  	hsw_package_c8_gpu_idle(dev_priv);
>  
>  	if (!i915.powersave)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index e5e1a5c..4c329e0 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -656,7 +656,7 @@ void intel_ddi_get_config(struct intel_encoder *encoder,
>  const char *intel_output_name(int output);
>  bool intel_has_pending_fb_unpin(struct drm_device *dev);
>  int intel_pch_rawclk(struct drm_device *dev);
> -void intel_mark_busy(struct drm_device *dev);
> +bool intel_mark_busy(struct drm_device *dev);
>  void intel_mark_fb_busy(struct drm_i915_gem_object *obj,
>  			struct intel_ring_buffer *ring);
>  void intel_mark_idle(struct drm_device *dev);
> -- 
> 1.7.9.5
>
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