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

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Date:   Mon, 4 Nov 2019 16:19:07 -0800
From:   Rob Clark <robdclark@...il.com>
To:     Brian Masney <masneyb@...tation.org>
Cc:     Rob Clark <robdclark@...omium.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Sean Paul <sean@...rly.run>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [Freedreno] drm/msm: 'pp done time out' errors after async commit changes

On Mon, Nov 4, 2019 at 4:01 PM Brian Masney <masneyb@...tation.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