[PATCH v2 10/10] drm/fb-helper: Acquire modeset lock around shadow-buffer flushing

[Sam Ravnborg]

On Fri, Nov 20, 2020 at 11:25:45AM +0100, Thomas Zimmermann wrote:
> Flushing the fbdev's shadow buffer requires vmap'ing the BO memory, which
> in turn requires pinning the BO. While being pinned, the BO cannot be moved
> into VRAM for scanout. Consequently, a concurrent modeset operation that
> involves the fbdev framebuffer would likely fail.
> 
> Resolve this problem be acquiring the modeset lock of the planes that use
> the fbdev framebuffer. On non-atomic drivers, also acquire the mode-config
> lock. This serializes the flushing of the framebuffer with concurrent
> modeset operations.
> 
> v2:
> 	* only acquire struct drm_fb_helper.lock in damage blitter (Daniel,
> 	  Christian)
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Acked-by: Sam Ravnborg <sam at ravnborg.org>