linux-kernel - Re: [PATCH] drm/msm/a6xx: fix bogus hwcg register updates

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Message-ID: <gofqva7heojs5d7hi2naihqlpkfttjocdazdg4yjqrkeqew5tw@bp57c7rvycpa>
Date: Fri, 23 Jan 2026 22:01:40 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Rob Clark <rob.clark@....qualcomm.com>,
        Neil Armstrong <neil.armstrong@...aro.org>
Cc: Johan Hovold <johan@...nel.org>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Akhil P Oommen <akhilpo@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Bjorn Andersson <andersson@...nel.org>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Subject: Re: [PATCH] drm/msm/a6xx: fix bogus hwcg register updates

On Thu, Jan 22, 2026 at 06:48:58AM -0800, Rob Clark wrote:
> On Thu, Jan 22, 2026 at 1:41 AM Johan Hovold <johan@...nel.org> wrote:
> >
> > [ +CC: Dave and Simona ]
> >
> > On Wed, Jan 21, 2026 at 08:59:51AM -0800, Rob Clark wrote:
> > > On Wed, Jan 21, 2026 at 7:17 AM Johan Hovold <johan@...nel.org> wrote:
> > > >
> > > > On Wed, Jan 14, 2026 at 09:56:12AM +0100, Johan Hovold wrote:
> > > > > On Sun, Dec 21, 2025 at 05:45:52PM +0100, Johan Hovold wrote:
> > > > > > The hw clock gating register sequence consists of register value pairs
> > > > > > that are written to the GPU during initialisation.
> > > > > >
> > > > > > The a690 hwcg sequence has two GMU registers in it that used to amount
> > > > > > to random writes in the GPU mapping, but since commit 188db3d7fe66
> > > > > > ("drm/msm/a6xx: Rebase GMU register offsets") they trigger a fault as
> > > > > > the updated offsets now lie outside the mapping. This in turn breaks
> > > > > > boot of machines like the Lenovo ThinkPad X13s.
> > > > > >
> > > > > > Note that the updates of these GMU registers is already taken care of
> > > > > > properly since commit 40c297eb245b ("drm/msm/a6xx: Set GMU CGC
> > > > > > properties on a6xx too"), but for some reason these two entries were
> > > > > > left in the table.
> > > > > >
> > > > > > Fixes: 5e7665b5e484 ("drm/msm/adreno: Add Adreno A690 support")
> > > > > > Cc: stable@...r.kernel.org  # 6.5
> > > > > > Cc: Bjorn Andersson <andersson@...nel.org>
> > > > > > Cc: Konrad Dybcio <konradybcio@...nel.org>
> > > > > > Signed-off-by: Johan Hovold <johan@...nel.org>
> > > > > > ---
> > > > >
> > > > > This one does not seem to have been applied yet despite fixing a
> > > > > critical regression in 6.19-rc1. I guess I could have highlighted that
> > > > > further by also including:
> > > > >
> > > > > Fixes: 188db3d7fe66 ("drm/msm/a6xx: Rebase GMU register offsets")
> > > > >
> > > > > I realise some delays are expected around Christmas, but can you please
> > > > > try to get this fix to Linus now that everyone should be back again?
> > > >
> > > > I haven't received any reply so was going to send another reminder, but
> > > > I noticed now that this patch was merged to the msm-next branch last
> > > > week.
> > > >
> > > > Since it fixes a regression in 6.19-rc1 it needs to go to Linus this
> > > > cycle and I would have assumed it should have be merged to msm-fixes.
> > > >
> > > > (MSM) DRM works in mysterious ways, so can someone please confirm that
> > > > this regression fix is heading into mainline for 6.19-final?
> > >
> > > Sorry, mesa 26.0 branchpoint this week so I've not had much time for
> > > kernel for last few weeks and didn't have time for a 2nd msm-fixes PR.
> > > But with fixes/cc tags it should be picked into 6.19.y
> >
> > I'm afraid that's not good enough as this is a *regression* breaking the
> > display completely on machines like the X13s.
> >
> > Regression fixes should go to mainline this cycle since we don't
> > knowingly break users' setups (and force them to debug/bisect when they
> > update to 6.19 while the fix has been available since before Christmas).
> >
> > Can't you just send a PR with this single fix? Otherwise, perhaps Dave
> > or Simona can pick up the fix directly?
> 
> Maybe someone can cherry-pick to drm-misc-fixes?

I know that there is some process for cherry-picking into
drm-misc-fixes, but I think the end result was frowned upon. Neil?

-- 
With best wishes
Dmitry