[Intel-gfx] [PATCH] drm/i915: VLV/CHV PSR: Increase wait delay time before active PSR.

[Daniel Vetter]

On Wed, Nov 19, 2014 at 07:38:51AM -0800, Rodrigo Vivi wrote:
> Since active function on VLV immediately activate PSR let's give more
> time for idleness.
> 
> v2: Rebase over intel_psr.c and fix typo.
> v3: s/psr/PSR on comment (by Durgadoss)
> 
> Reviewed-by: Durgadoss R <durgadoss.r at intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_psr.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> index dd0e6e0..57bf6d4 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -597,6 +597,11 @@ void intel_psr_flush(struct drm_device *dev,
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_crtc *crtc;
>  	enum pipe pipe;
> +	/* On HSW/BDW Hardware controls idle_frames to go to PSR entry state
> +	 * However on VLV we go to PSR active state with PSR work. So let's
> +	 * wait more time and let the user experience smooth enough.
> +	 */
> +	int delay = msecs_to_jiffies(HAS_DDI(dev) ? 100 : 5000);

I'd like to know how we arrived at this number? And the justification imo
doesn't make a lot of sense, whether it's hw or sw entering psr state
doesn't take a lot of cpu cycles. Two things:

- Should we compute this delay according to the minimal psr exit frames we
  already get from vbt and use for hsw/bdw?
- Do we need to adjust igt testcases to wait longer with this 5s delay?

I'll punt on this patch for now until this is resolved.
-Daniel

>  
>  	mutex_lock(&dev_priv->psr.lock);
>  	if (!dev_priv->psr.enabled) {
> @@ -631,7 +636,7 @@ void intel_psr_flush(struct drm_device *dev,
>  
>  	if (!dev_priv->psr.active && !dev_priv->psr.busy_frontbuffer_bits)
>  		schedule_delayed_work(&dev_priv->psr.work,
> -				      msecs_to_jiffies(100));
> +				      msecs_to_jiffies(delay));
>  	mutex_unlock(&dev_priv->psr.lock);
>  }
>  
> -- 
> 1.9.3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch