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

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@suse.de

Acked-by: Sam Ravnborg sam@ravnborg.org