linux-kernel - Re: [PATCH] drm/msm: Fix double pm_runtime

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Date:   Mon, 6 Jun 2022 14:23:34 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm: Fix double pm_runtime_disable() call

On Mon, Jun 6, 2022 at 2:13 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
>
> Following commit 17e822f7591f ("drm/msm: fix unbalanced
> pm_runtime_enable in adreno_gpu_{init, cleanup}"), any call to
> adreno_unbind() will disable runtime PM twice, as indicated by the call
> trees below:
>
>   adreno_unbind()
>    -> pm_runtime_force_suspend()
>    -> pm_runtime_disable()
>
>   adreno_unbind()
>    -> gpu->funcs->destroy() [= aNxx_destroy()]
>    -> adreno_gpu_cleanup()
>    -> pm_runtime_disable()
>
> Note that pm_runtime_force_suspend() is called right before
> gpu->funcs->destroy() and both functions are called unconditionally.
>
> With recent addition of the eDP AUX bus code, this problem manifests
> itself when the eDP panel cannot be found yet and probing is deferred.
> On the first probe attempt, we disable runtime PM twice as described
> above. This then causes any later probe attempt to fail with
>
>   [drm:adreno_load_gpu [msm]] *ERROR* Couldn't power up the GPU: -13
>
> preventing the driver from loading.
>
> As there seem to be scenarios where the aNxx_destroy() functions are not
> called from adreno_unbind(), simply removing pm_runtime_disable() from
> inside adreno_unbind() does not seem to be the proper fix. This is what
> commit 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in
> adreno_gpu_{init, cleanup}") intended to fix. Therefore, instead check
> whether runtime PM is still enabled, and only disable it in that case.
>
> Fixes: 17e822f7591f ("drm/msm: fix unbalanced pm_runtime_enable in adreno_gpu_{init, cleanup}")
> Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>

Reviewed-by: Rob Clark <robdclark@...il.com>

> ---
>  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index 4e665c806a14..f944b69e2a25 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -1057,7 +1057,8 @@ void adreno_gpu_cleanup(struct adreno_gpu *adreno_gpu)
>         for (i = 0; i < ARRAY_SIZE(adreno_gpu->info->fw); i++)
>                 release_firmware(adreno_gpu->fw[i]);
>
> -       pm_runtime_disable(&priv->gpu_pdev->dev);
> +       if (pm_runtime_enabled(&priv->gpu_pdev->dev))
> +               pm_runtime_disable(&priv->gpu_pdev->dev);
>
>         msm_gpu_cleanup(&adreno_gpu->base);
>  }
> --
> 2.36.1
>