linux-kernel - Re: [PATCH] drm/msm/adreno: adreno_gpu: Use suspend() instead of idle() on load error

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Message-ID: <ZCRNFitcrAeH27Pn@hovoldconsulting.com>
Date:   Wed, 29 Mar 2023 16:37:10 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org, marijn.suijten@...ainline.org,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Johan Hovold <johan+linaro@...nel.org>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Nathan Chancellor <nathan@...nel.org>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/adreno: adreno_gpu: Use suspend() instead of
 idle() on load error

On Wed, Mar 29, 2023 at 04:04:44PM +0200, Konrad Dybcio wrote:
> If we fail to initialize the GPU for whatever reason (say we don't
> embed the GPU firmware files in the initrd), the error path involves
> pm_runtime_put_sync() which then calls idle() instead of suspend().
> 
> This is suboptimal, as it means that we're not going through the
> clean shutdown sequence. With at least A619_holi, this makes the GPU
> not wake up until it goes through at least one more start-fail-stop
> cycle. Fix that by using pm_runtime_put_sync_suspend to force a clean
> shutdown.

This does not sound right. If pm_runtime_put_sync() fails to suspend the
device when the usage count drops to zero, then you have a bug somewhere
else.

Also since commit 2c087a336676 ("drm/msm/adreno: Load the firmware
before bringing up the hardware") the firmware is loaded before even
hitting these paths so the above description does not sound right in
that respect either (or is missing some details).

> Test cases:
> 1. firmware baked into kernel
> 2. error loading fw in initrd -> load from rootfs at DE start
> 
> Both succeed on A619_holi (SM6375) and A630 (SDM845).
> 
> Fixes: 0d997f95b70f ("drm/msm/adreno: fix runtime PM imbalance at gpu load")
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>  drivers/gpu/drm/msm/adreno/adreno_device.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
> index f61896629be6..59f3302e8167 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> @@ -477,7 +477,7 @@ struct msm_gpu *adreno_load_gpu(struct drm_device *dev)
>  	return gpu;
>  
>  err_put_rpm:
> -	pm_runtime_put_sync(&pdev->dev);
> +	pm_runtime_put_sync_suspend(&pdev->dev);
>  err_disable_rpm:
>  	pm_runtime_disable(&pdev->dev);

Johan