[PATCH] drm/imx: move arming of the vblank event to atomic_flush

[Philipp Zabel]

On Thu, 2018-03-15 at 10:11 +0100, Lucas Stach wrote:
> Right now the vblank event completion is racing with the atomic update,
> which is especially bad when the PRE is in use, as one of the hardware
> issue workaround might extend the atomic commit for quite some time.
> 
> If the vblank IRQ happens to trigger during that time, we will prematurely
> signal the atomic commit completion to userspace, which causes tearing
> when userspace re-uses a framebuffer we haven't managed to flip away from
> yet.
> 
> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>

This trades the tiny (on i.MX6Q) or not so tiny (on i.MX6QP) risk of
returning a vblank event completion too early for the tiny risk to miss
a vsync interrupt, and to return a vblank event completion a frame too
late. Applied to imx-drm/fixes.

regards
Philipp