Re: [PATCH] drm/msm: Fix double pm_runtime_disable() call

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Mon 06 Jun 14:13 PDT 2022, Maximilian Luz 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}")

Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>

> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.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
>