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

[Tarun Vyas]

On Mon, Jul 09, 2018 at 11:30:00AM -0700, Dhinakaran Pandiyan wrote:
> 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.
>
That's right. On my KBL chromebook that's running the drm-tip, when I plug-in an external display, so pipe B,
I see "[drm:intel_pipe_update_start] *ERROR* PSR idle timed out, atomic update may fail on pipe B", Iadded the pipe
name in the DRM_ERROR, may be I should make that change in the v3 of this patch along with updating the commit message.

But, yea, this proves that with the CAN_PSR check, the non-PSR pipes (B/C) wait on pipe-A to exit PSR which doesn't have
any reason to do so at that moment, hence the error.

I'll make the commit message changes and add the pipe name in the DRM_ERROR as well ?
> > 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 at intel.com>
> > Signed-off-by: Tarun Vyas <tarun.vyas at 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();