linux-kernel - Re: [PATCH] drm/msm/gpu: Fix crash on devices without devfreq support

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Date:   Wed, 23 Feb 2022 06:11:28 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...omium.org>,
        Linux Kernel Functional Testing <lkft@...aro.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/gpu: Fix crash on devices without devfreq support

On 19/02/2022 21:33, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> Avoid going down devfreq paths on devices where devfreq is not
> initialized.
> 
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> Reported-by: Anders Roxell <anders.roxell@...aro.org>
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
>   drivers/gpu/drm/msm/msm_gpu_devfreq.c | 31 +++++++++++++++++++++------
>   1 file changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> index 9bf319be11f6..26a3669a97b3 100644
> --- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> +++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> @@ -83,12 +83,17 @@ static struct devfreq_dev_profile msm_devfreq_profile = {
>   static void msm_devfreq_boost_work(struct kthread_work *work);
>   static void msm_devfreq_idle_work(struct kthread_work *work);
>   
> +static bool has_devfreq(struct msm_gpu *gpu)
> +{
> +	return !!gpu->funcs->gpu_busy;

I see that devfreq init will be skipped if gpu_busy is NULL.
Can we use gpu->devfreq instead of this condition?

I noticed that you have replaced some of gpu->devfreq checks with 
has_devreq() calls. Is there any difference?

> +}
> +
>   void msm_devfreq_init(struct msm_gpu *gpu)
>   {
>   	struct msm_gpu_devfreq *df = &gpu->devfreq;
>   
>   	/* We need target support to do devfreq */
> -	if (!gpu->funcs->gpu_busy)
> +	if (!has_devfreq(gpu))
>   		return;
>   
>   	dev_pm_qos_add_request(&gpu->pdev->dev, &df->idle_freq,
> @@ -149,6 +154,9 @@ void msm_devfreq_cleanup(struct msm_gpu *gpu)
>   {
>   	struct msm_gpu_devfreq *df = &gpu->devfreq;
>   
> +	if (!has_devfreq(gpu))
> +		return;
> +
>   	devfreq_cooling_unregister(gpu->cooling);
>   	dev_pm_qos_remove_request(&df->boost_freq);
>   	dev_pm_qos_remove_request(&df->idle_freq);
> @@ -156,16 +164,24 @@ void msm_devfreq_cleanup(struct msm_gpu *gpu)
>   
>   void msm_devfreq_resume(struct msm_gpu *gpu)
>   {
> -	gpu->devfreq.busy_cycles = 0;
> -	gpu->devfreq.time = ktime_get();
> +	struct msm_gpu_devfreq *df = &gpu->devfreq;
>   
> -	devfreq_resume_device(gpu->devfreq.devfreq);
> +	if (!has_devfreq(gpu))
> +		return;
> +
> +	df->busy_cycles = 0;
> +	df->time = ktime_get();
> +
> +	devfreq_resume_device(df->devfreq);
>   }
>   
>   void msm_devfreq_suspend(struct msm_gpu *gpu)
>   {
>   	struct msm_gpu_devfreq *df = &gpu->devfreq;
>   
> +	if (!has_devfreq(gpu))
> +		return;
> +
>   	devfreq_suspend_device(df->devfreq);
>   
>   	cancel_idle_work(df);
> @@ -185,6 +201,9 @@ void msm_devfreq_boost(struct msm_gpu *gpu, unsigned factor)
>   	struct msm_gpu_devfreq *df = &gpu->devfreq;
>   	uint64_t freq;
>   
> +	if (!has_devfreq(gpu))
> +		return;
> +
>   	freq = get_freq(gpu);
>   	freq *= factor;
>   
> @@ -207,7 +226,7 @@ void msm_devfreq_active(struct msm_gpu *gpu)
>   	struct devfreq_dev_status status;
>   	unsigned int idle_time;
>   
> -	if (!df->devfreq)
> +	if (!has_devfreq(gpu))
>   		return;
>   
>   	/*
> @@ -253,7 +272,7 @@ void msm_devfreq_idle(struct msm_gpu *gpu)
>   {
>   	struct msm_gpu_devfreq *df = &gpu->devfreq;
>   
> -	if (!df->devfreq)
> +	if (!has_devfreq(gpu))
>   		return;
>   
>   	msm_hrtimer_queue_work(&df->idle_work, ms_to_ktime(1),


-- 
With best wishes
Dmitry