[Intel-gfx] [RFC] drm/i915: don't wait_for_vblank if the CRTC is disabled

[Matt Roper]

On Wed, Mar 18, 2015 at 04:15:07PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> 
> Otherwise we'll get a WARN from drm_wait_one_vblank() saying that
> vblanks are not available (since they were already disabled in
> crtc_disable()).
> 
> This is certainly a regresison, but QA couldn't bisect it due to
> other regressions breaking the bisect.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89550
> Testcase: igt/pm_rpm/legacy-planes
> Testcase: igt/pm_rpm/legacy-planes-dpms
> Testcase: igt/pm_rpm/universal-planes
> Testcase: igt/pm_rpm/universal-planes-dpms
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> 
> I'm not really sure if this is the best way to fix the regression. Ville and/or
> Matt should provide some comments here.
> 

This will definitely fix the problem (we shouldn't be waiting for vblank
with a disabled CRTC!), but I think the true bug in our code is that our
sprite commit function is setting some bits that should have been set
back in the 'check' phase under the 'if (intel_crtc->active)' branch.

I'll supply a patch shortly that I think should fix how we got into this
situation in the first place.  The whole 'wait_for_vblank' flag is
something we should be able to get rid of completely once I finish the
atomic watermark work.


Matt

> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index f1c0295..f2f7e81 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12193,7 +12193,7 @@ static void intel_finish_crtc_commit(struct drm_crtc *crtc)
>  
>  	intel_runtime_pm_put(dev_priv);
>  
> -	if (intel_crtc->atomic.wait_vblank)
> +	if (intel_crtc->active && intel_crtc->atomic.wait_vblank)
>  		intel_wait_for_vblank(dev, intel_crtc->pipe);
>  
>  	intel_frontbuffer_flip(dev, intel_crtc->atomic.fb_bits);
> -- 
> 2.1.4
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795