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Subject: Re: [2/2] drm/msm: Add support for GPU cooling
To:     mka@chromium.org
Cc:     freedreno@lists.freedesktop.org, robh@kernel.org,
        robdclark@gmail.com, linux-arm-msm@vger.kernel.org,
        dri-devel@freedesktop.org, linux-kernel@vger.kernel.org
References: <1602176947-17385-2-git-send-email-akhilpo@codeaurora.org>
 <20201009183640.GB1292413@google.com>
From:   Akhil P Oommen <akhilpo@codeaurora.org>
Message-ID: <cab2105e-7a8c-988f-dcc1-056692a94e8b@codeaurora.org>
Date:   Mon, 12 Oct 2020 19:03:51 +0530
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On 10/10/2020 12:06 AM, mka@chromium.org wrote:
> 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@codeaurora.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.
> Why do you think this is not the correct order? If you are thinking 
about devfreq struct, it is managed device resource.

-Akhil