linux-kernel - Re: [PATCH v2 1/2] drm/msm/dpu1: don't choke on disabling the writeback connector

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Message-ID: <f0d1da69-d52a-484e-8255-b9639c358a71@lausen.nl>
Date: Wed, 7 Aug 2024 11:41:18 -0400
From: Leonard Lausen <leonard@...sen.nl>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Rob Clark <robdclark@...il.com>, Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 Jeykumar Sankaran <jsanka@...eaurora.org>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] drm/msm/dpu1: don't choke on disabling the
 writeback connector

On 8/7/24 06:44, Dmitry Baryshkov wrote:> Could you please clarify, I was under the impression that currently whole suspend/resume is broken, so it's more than a dmesg message.

71174f362d67 specifically, or v6.9 more broadly regress in that we get "[dpu
error]connector not connected 3" and "[drm:drm_mode_config_helper_resume]
*ERROR* Failed to resume (-22)" if suspending and resuming the system while
external display is connected over USB-C DP. Suspend and resume itself
still works, and the external display also works after the resume, albeit
perhaps with a small delay due to the dpu error. This is also mentioned in
the issue description of https://gitlab.freedesktop.org/drm/msm/-/issues/57.
So while suspend/resume isn't fully broken, the error is still unexpected and
I thus bisected and identified 71174f362d67 as the first commit to trigger it.
While your patch avoids the dpu/drm error, it triggers issue with the CRTC state,
breaking the CRTC functionality after resume.

Might we be facing a race condition here, which is accidentally exposed by
71174f362d67 but requires a separate fix?