linux-kernel - Re: [PATCH 1/2] adreno: Shutdown the GPU properly

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Date:   Sat, 12 Nov 2022 10:44:33 -0800
From:   Rob Clark <robdclark@...il.com>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, Rob Clark <robdclark@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Ross Zwisler <zwisler@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        dri-devel@...ts.freedesktop.org, Emma Anholt <emma@...olt.net>,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Sean Paul <sean@...rly.run>,
        Vladimir Lypak <vladimir.lypak@...il.com>
Subject: Re: [PATCH 1/2] adreno: Shutdown the GPU properly

On Fri, Nov 11, 2022 at 1:08 PM Joel Fernandes <joel@...lfernandes.org> wrote:
>
>
>
> > On Nov 11, 2022, at 2:50 PM, Joel Fernandes (Google) <joel@...lfernandes.org> wrote:
> >
> > During kexec on ARM device, we notice that device_shutdown() only calls
> > pm_runtime_force_suspend() while shutting down the GPU. This means the GPU
> > kthread is still running and further, there maybe active submits.
> >
> > This causes all kinds of issues during a kexec reboot:
> >
> > Warning from shutdown path:
> >
> > [  292.509662] WARNING: CPU: 0 PID: 6304 at [...] adreno_runtime_suspend+0x3c/0x44
> > [  292.509863] Hardware name: Google Lazor (rev3 - 8) with LTE (DT)
> > [  292.509872] pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [  292.509881] pc : adreno_runtime_suspend+0x3c/0x44
> > [  292.509891] lr : pm_generic_runtime_suspend+0x30/0x44
> > [  292.509905] sp : ffffffc014473bf0
> > [...]
> > [  292.510043] Call trace:
> > [  292.510051]  adreno_runtime_suspend+0x3c/0x44
> > [  292.510061]  pm_generic_runtime_suspend+0x30/0x44
> > [  292.510071]  pm_runtime_force_suspend+0x54/0xc8
> > [  292.510081]  adreno_shutdown+0x1c/0x28
> > [  292.510090]  platform_shutdown+0x2c/0x38
> > [  292.510104]  device_shutdown+0x158/0x210
> > [  292.510119]  kernel_restart_prepare+0x40/0x4c
> >
> > And here from GPU kthread, an SError OOPs:
> >
> > [  192.648789]  el1h_64_error+0x7c/0x80
> > [  192.648812]  el1_interrupt+0x20/0x58
> > [  192.648833]  el1h_64_irq_handler+0x18/0x24
> > [  192.648854]  el1h_64_irq+0x7c/0x80
> > [  192.648873]  local_daif_inherit+0x10/0x18
> > [  192.648900]  el1h_64_sync_handler+0x48/0xb4
> > [  192.648921]  el1h_64_sync+0x7c/0x80
> > [  192.648941]  a6xx_gmu_set_oob+0xbc/0x1fc
> > [  192.648968]  a6xx_hw_init+0x44/0xe38
> > [  192.648991]  msm_gpu_hw_init+0x48/0x80
> > [  192.649013]  msm_gpu_submit+0x5c/0x1a8
> > [  192.649034]  msm_job_run+0xb0/0x11c
> > [  192.649058]  drm_sched_main+0x170/0x434
> > [  192.649086]  kthread+0x134/0x300
> > [  192.649114]  ret_from_fork+0x10/0x20
> >
> > Fix by calling adreno_system_suspend() in the device_shutdown() path.
> >
> > Cc: Rob Clark <robdclark@...omium.org>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Ricardo Ribalda <ribalda@...omium.org>
> > Cc: Ross Zwisler <zwisler@...nel.org>
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> > ---
> > drivers/gpu/drm/msm/adreno/adreno_device.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
> > index 24b489b6129a..f0cff62812c3 100644
> > --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> > +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> > @@ -607,9 +607,12 @@ static int adreno_remove(struct platform_device *pdev)
> >    return 0;
> > }
> >
> > +static int adreno_system_suspend(struct device *dev);
> > static void adreno_shutdown(struct platform_device *pdev)
> > {
> > -    pm_runtime_force_suspend(&pdev->dev);
> > +    struct msm_gpu *gpu = dev_to_gpu(&pdev->dev);
> > +
>
> This local variable definition should go to patch 2/2. Will fix in v2.
>
> Thanks,
>
>  - Joel
>
>
> > +    WARN_ON_ONCE(adreno_system_suspend(&pdev->dev));

I think maybe adreno_unbind() needs the same treatment?  Any path
where we yank out the power cord without ensuring the scheduler is
parked means we'd be racing with jobs in the scheduler queue.  Ie.
userspace could queue a job before it is frozen, but the drm/scheduler
kthread hasn't yet called the msm_job_run() callback (which does
various touching of the now powered off hw).  So I think we need to
ensure that the scheduler is parked in all paths that call
pm_runtime_force_suspend() (as that bypasses the runpm reference that
would otherwise unsure the hw is powered before msm_job_run pokes at
registers)

BR,
-R

> > }
> >
> > static const struct of_device_id dt_match[] = {
> > --
> > 2.38.1.493.g58b659f92b-goog
> >