Re: [PATCH v2] drm/i915: Use crtc_state->has_psr instead of CAN_PSR for pipe update

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Sun, 2018-07-08 at 18:46 -0700, Tarun Vyas wrote:
> In commit "drm/i915: Wait for PSR exit before checking for vblank
> evasion", the idea was to limit the PSR IDLE checks when PSR is
> actually supported. While CAN_PSR does do that check, it doesn't
> applies on a per-crtc basis. crtc_state->has_psr is a more granular
> check that avoids everything but pipe A, for the PSR IDLE check.
> 
> With this, the PSR IDLE check should be a *no-op* for all but pipe A
> which is what was intended originally.
> 

So, the problem is when we update a non-PSR pipe (B or C) and PSR is
active on another pipe(A, specifically), we end up waiting for the pipe
A MMIO to become idle.

Can you please update the commit message as the commit message makes
the per-pipe check sound like an optimization? 

This also points to a gap in our testing, I don't see a two pipe PSR
related IGT.

> Fixes: a608987970b9 ("drm/i915: Wait for PSR exit before checking for
> vblank evasion")
> 
> v2: Remove unnecessary parantheses, make checkpatch happy.
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Tarun Vyas <tarun.vyas@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_sprite.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_sprite.c
> b/drivers/gpu/drm/i915/intel_sprite.c
> index 4990d6e84ddf..83880e3a5f3d 100644
> --- a/drivers/gpu/drm/i915/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> @@ -118,7 +118,7 @@ void intel_pipe_update_start(const struct
> intel_crtc_state *new_crtc_state)
>  	 * VBL interrupts will start the PSR exit and prevent a PSR
>  	 * re-entry as well.
>  	 */
> -	if (CAN_PSR(dev_priv) && intel_psr_wait_for_idle(dev_priv))
> +	if (new_crtc_state->has_psr &&
> intel_psr_wait_for_idle(dev_priv))
>  		DRM_ERROR("PSR idle timed out, atomic update may
> fail\n");
>  
>  	local_irq_disable();
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