Re: [Intel-gfx] [PATCH] drm/i915: Don't clobber crtc->fb when queue_flip fails

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

ville.syrjala@linux.intel.com writes:

> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Point crtc->fb the the new framebuffer only after we know that the flip
> was succesfully queued.
>
> While at it, move the intel_fb and obj assignments a bit close to where
> they're used.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> It looks like Mika hit this rather easily in his ARB_robustness work.
> Waiting for him to confirm whether this really fixes the pin_count
> underflow bug he's seeing.

Tested-by: Mika Kuoppala <mika.kuoppala@intel.com>

>  drivers/gpu/drm/i915/intel_display.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 0ff10b3..e7684f1 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -7311,9 +7311,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
>  	intel_crtc->unpin_work = work;
>  	spin_unlock_irqrestore(&dev->event_lock, flags);
>  
> -	intel_fb = to_intel_framebuffer(fb);
> -	obj = intel_fb->obj;
> -
>  	if (atomic_read(&intel_crtc->unpin_work_count) >= 2)
>  		flush_workqueue(dev_priv->wq);
>  
> @@ -7321,12 +7318,13 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
>  	if (ret)
>  		goto cleanup;
>  
> +	intel_fb = to_intel_framebuffer(fb);
> +	obj = intel_fb->obj;
> +
>  	/* Reference the objects for the scheduled work. */
>  	drm_gem_object_reference(&work->old_fb_obj->base);
>  	drm_gem_object_reference(&obj->base);
>  
> -	crtc->fb = fb;
> -
>  	work->pending_flip_obj = obj;
>  
>  	work->enable_stall_check = true;
> @@ -7338,6 +7336,8 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
>  	if (ret)
>  		goto cleanup_pending;
>  
> +	crtc->fb = fb;
> +
>  	intel_disable_fbc(dev);
>  	intel_mark_fb_busy(obj);
>  	mutex_unlock(&dev->struct_mutex);
> -- 
> 1.7.12.4
>
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