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

[Akhil P Oommen]

On 10/10/2020 12:06 AM, mka@xxxxxxxxxxxx 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@xxxxxxxxxxxxxx>
> > ---
> >   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