[Freedreno] drm/msm: 'pp done time out' errors after async commit changes

[Rob Clark]

On Mon, Nov 4, 2019 at 4:01 PM Brian Masney <masneyb at onstation.org> wrote:
>
> Hey Rob,
>
> Since commit 2d99ced787e3 ("drm/msm: async commit support"), the frame
> buffer console on my Nexus 5 began throwing these errors:
>
> msm fd900000.mdss: pp done time out, lm=0
>
> The display still works.
>
> I see that mdp5_flush_commit() was introduced in commit 9f6b65642bd2
> ("drm/msm: add kms->flush_commit()") with a TODO comment and the commit
> description mentions flushing registers. I assume that this is the
> proper fix. If so, can you point me to where these registers are
> defined and I can work on the mdp5 implementation.

See mdp5_ctl_commit(), which writes the CTL_FLUSH registers.. the idea
would be to defer writing CTL_FLUSH[ctl_id] = flush_mask until
kms->flush() (which happens from a timer shortly before vblank).

But I think the async flush case should not come up with fbcon?  It
was really added to cope with hwcursor updates (and userspace that
assumes it can do an unlimited # of cursor updates per frame).. the
intention was that nothing should change in the sequence for mdp5 (but
I guess that was not the case).

BR,
-R