linux-kernel - Re: [2/2] drm/msm: Add support for GPU cooling

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Date:   Fri, 9 Oct 2020 11:36:40 -0700
From:   mka@...omium.org
To:     Akhil P Oommen <akhilpo@...eaurora.org>
Cc:     freedreno@...ts.freedesktop.org, robh@...nel.org,
        robdclark@...il.com, linux-arm-msm@...r.kernel.org,
        dri-devel@...edesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [2/2] drm/msm: Add support for GPU cooling

Hi Akhil,

On Thu, Oct 08, 2020 at 10:39:07PM +0530, Akhil P Oommen wrote:
> Register GPU as a devfreq cooling device so that it can be passively
> cooled by the thermal framework.
> 
> Signed-off-by: Akhil P Oommen <akhilpo@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/msm_gpu.c | 13 ++++++++++++-
>  drivers/gpu/drm/msm/msm_gpu.h |  2 ++
>  2 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index 55d1648..93ffd66 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -14,6 +14,7 @@
>  #include <generated/utsrelease.h>
>  #include <linux/string_helpers.h>
>  #include <linux/devfreq.h>
> +#include <linux/devfreq_cooling.h>
>  #include <linux/devcoredump.h>
>  #include <linux/sched/task.h>
>  
> @@ -107,9 +108,18 @@ static void msm_devfreq_init(struct msm_gpu *gpu)
>  	if (IS_ERR(gpu->devfreq.devfreq)) {
>  		DRM_DEV_ERROR(&gpu->pdev->dev, "Couldn't initialize GPU devfreq\n");
>  		gpu->devfreq.devfreq = NULL;
> +		return;
>  	}
>  
>  	devfreq_suspend_device(gpu->devfreq.devfreq);
> +
> +	gpu->cooling = of_devfreq_cooling_register(gpu->pdev->dev.of_node,
> +			gpu->devfreq.devfreq);
> +	if (IS_ERR(gpu->cooling)) {
> +		DRM_DEV_ERROR(&gpu->pdev->dev,
> +				"Couldn't register GPU cooling device\n");
> +		gpu->cooling = NULL;
> +	}
>  }
>  
>  static int enable_pwrrail(struct msm_gpu *gpu)
> @@ -926,7 +936,6 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>  
>  	msm_devfreq_init(gpu);
>  
> -
>  	gpu->aspace = gpu->funcs->create_address_space(gpu, pdev);
>  
>  	if (gpu->aspace == NULL)
> @@ -1005,4 +1014,6 @@ void msm_gpu_cleanup(struct msm_gpu *gpu)
>  		gpu->aspace->mmu->funcs->detach(gpu->aspace->mmu);
>  		msm_gem_address_space_put(gpu->aspace);
>  	}
> +
> +	devfreq_cooling_unregister(gpu->cooling);

Resources should be released in reverse order, otherwise the cooling device
could use resources that have already been freed.