linux-kernel - Re: [PATCH] drm/msm/gpu: Drop qos request if devm_devfreq_add

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Date:   Mon, 1 Aug 2022 10:38:41 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
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>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/gpu: Drop qos request if devm_devfreq_add_device()
 fails

On Fri, Jul 8, 2022 at 9:24 AM Bjorn Andersson
<bjorn.andersson@...aro.org> wrote:
>
> In the event that devm_devfreq_add_device() fails the device's qos freq
> list is left referencing df->idle_freq and df->boost_freq. Attempting to
> initialize devfreq again after a probe deferral will then cause invalid
> memory accesses in dev_pm_qos_add_request().
>
> Fix this by dropping the requests in the error path.
>
> Fixes: 7c0ffcd40b16 ("drm/msm/gpu: Respect PM QoS constraints")
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>

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

> ---
>  drivers/gpu/drm/msm/msm_gpu_devfreq.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> index c2ea978c8921..21e271a318ee 100644
> --- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> +++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> @@ -198,6 +198,8 @@ void msm_devfreq_init(struct msm_gpu *gpu)
>
>         if (IS_ERR(df->devfreq)) {
>                 DRM_DEV_ERROR(&gpu->pdev->dev, "Couldn't initialize GPU devfreq\n");
> +               dev_pm_qos_remove_request(&df->idle_freq);
> +               dev_pm_qos_remove_request(&df->boost_freq);
>                 df->devfreq = NULL;
>                 return;
>         }
> --
> 2.35.1
>