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From:   Doug Anderson <dianders@chromium.org>
Date:   Thu, 27 May 2021 16:14:17 -0700
Message-ID: <CAD=FV=UQzM=cEsEYbR4QwaovT377dn4vLxqcK7xrLMutZPVDeQ@mail.gmail.com>
Subject: Re: [v1] drm/msm/disp/dpu1: avoid perf update in frame done event
To:     Krishna Manikandan <mkrishn@codeaurora.org>
Cc:     dri-devel <dri-devel@lists.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Rob Clark <robdclark@gmail.com>,
        Sean Paul <seanpaul@chromium.org>,
        Kalyan Thota <kalyan_t@codeaurora.org>,
        Stephen Boyd <swboyd@chromium.org>
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Hi,

On Wed, May 26, 2021 at 10:08 PM Krishna Manikandan
<mkrishn@codeaurora.org> wrote:
>
> Crtc perf update from frame event work can result in
> wrong bandwidth and clock update from dpu if the work
> is scheduled after the swap state has happened.
>
> Avoid such issues by moving perf update to complete
> commit once the frame is accepted by the hardware.
>
> Fixes: a29c8c024165 ("drm/msm/disp/dpu1: fix display underruns during modeset")
> Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

I don't know much about this code or any of the theory behind it, but
I can confirm that this fixes the hang I was seeing with the previous
patch. On sc7180-trogdor-lazor:

Tested-by: Douglas Anderson <dianders@chromium.org>