On Mon, Oct 12, 2020 at 07:03:51PM +0530, Akhil P Oommen wrote:
> On 10/10/2020 12:06 AM, m...@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 <akhi...@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.
I did not check specifically if changing the frequency really uses any of the
resources that are released previously, In any case it's not a good idea to
allow other parts of the kernel to use a half initialized/torn down device.
Even if it isn't a problem today someone could change the driver to use any
of these resources (or add a new one) in a frequency change, without even
thinking about the cooling device, just (rightfully) asuming that things are
set up and torn down in a sane order.
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