[Intel-gfx] [PATCH 4/5] drm/i915: Invalidate frontbuffer bits on FBDEV sync

[Daniel Vetter]

On Thu, Jun 18, 2015 at 11:43:25AM -0700, Rodrigo Vivi wrote:
> @@ -259,6 +269,15 @@ void intel_frontbuffer_flip_complete(struct drm_device *dev,
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  
>  	mutex_lock(&dev_priv->fb_tracking.lock);
> +
> +	/*
> +	 * Let's assume that if this asynchronous flip happened
> +	 * FBDEV might not be in use anymore.
> +	 * If this is not the case fb_sync will happen on next
> +	 * frontbuffer touch and invalidate bits again
> +	 */
> +	dev_priv->fb_tracking.fbdev_running = false;

This pretty much destroys frontbuffer tracking for everyone if they boot
up with fbdev.

Since this seems to be epic fun indeed I think what we need to do is:
- Fill out the ->dirty callback.
- Extend the drm fbdev helpers to call ->dirty at all suitable places if
  needed.
 
For an example of how to do this all see udl/udl_fb.c. Imo a good patch
would be to replace all the udl special casing with the new fbdev helpers,
just as a demonstration patch. i915 isn't the only driver where every
frontbuffer change must involve some manual driver action, there's no
reason we need to roll our own solution.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch