Re: [PATCH 1/4] drm/i915: Keep plane->state updated on pageflip

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jan 30, 2015 at 04:22:36PM -0800, Matt Roper wrote:
> Until all drivers have transitioned to atomic, the framebuffer
> associated with a plane is tracked in both plane->fb (for legacy) and
> plane->state->fb (for all the new atomic codeflow).  All of our modeset
> and plane updates use drm_plane->update_plane(), so in theory plane->fb
> and plane->state->fb should always stay in sync and point at the same
> thing for i915.  However we forgot about the pageflip ioctl case, which
> currently only updates plane->fb and leaves plane->state->fb at a stale
> value.
> 
> Surprisingly, this doesn't cause any real problems at the moment since
> internally we use the plane->fb pointer in most of the places that
> matter, and on the next .update_plane() call, we use plane->fb to figure
> out which framebuffer to cleanup.  However when we switch to the full
> atomic helpers for update_plane()/disable_plane(), those helpers use
> plane->state->fb to figure out which framebuffer to cleanup, so not
> having updated the plane->state->fb pointer causes things to blow up
> following a pageflip ioctl.
> 
> The fix here is to just make sure we update plane->state->fb at the same
> time we update plane->fb in the pageflip ioctl.
> 
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 3d220a6..08e2bab 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -9801,6 +9801,13 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
>  
>  	crtc->primary->fb = fb;
>  
> +	/* Keep state structure in sync */
> +	if (crtc->primary->state->fb)
> +		drm_framebuffer_unreference(crtc->primary->state->fb);
> +	crtc->primary->state->fb = fb;
> +	if (crtc->primary->state->fb)
> +		drm_framebuffer_reference(crtc->primary->state->fb);

Yeah, I had the same fixup in my own testconversion. So merged this and
the 2nd patch to dinq (for 3.21).

Thanks, Daniel
> +
>  	work->pending_flip_obj = obj;
>  
>  	atomic_inc(&intel_crtc->unpin_work_count);
> -- 
> 1.8.5.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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