[PATCH] drm/amdgpu: take runtime pm reference when we attach a buffer

[Shashank Sharma]

On 10/12/20 3:58 pm, Christian König wrote:
> Am 10.12.20 um 05:49 schrieb Shashank Sharma:
>> On 09/12/20 11:00 pm, Alex Deucher wrote:
>>> On Fri, Dec 4, 2020 at 3:41 PM Alex Deucher <alexdeucher at gmail.com> wrote:
>>>> And drop it when we detach.  If the shared buffer is in vram,
>>>> we need to make sure we don't put the device into runtime
>>>> suspend.
>>>>
>>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>>> Ping?  Any thoughts on this?  We really only need this for p2p since
>>> device memory in involved, but I'm not sure of the best way to handle
>>> that.
>>>
>>> Alex
>>>
>>>
>>>> ---
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 16 ++++++++++++++--
>>>>   1 file changed, 14 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>>>> index 5b465ab774d1..f63f182f37f9 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>>>> @@ -40,6 +40,7 @@
>>>>   #include <linux/dma-buf.h>
>>>>   #include <linux/dma-fence-array.h>
>>>>   #include <linux/pci-p2pdma.h>
>>>> +#include <linux/pm_runtime.h>
>>>>
>>>>   /**
>>>>    * amdgpu_gem_prime_vmap - &dma_buf_ops.vmap implementation
>>>> @@ -187,9 +188,13 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
>>>>          if (attach->dev->driver == adev->dev->driver)
>>>>                  return 0;
>>>>
>>>> +       r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
>>>> +       if (r < 0)
>>>> +               goto out;
>>>> +
>> I am a bit skeptical if we should fail the BO reserve if we don't get the sync ? I was hoping to continue with it, with a warning maybe, so that it doesn't block the existing functionality ?
> I'm not sure why pm_runtime_get_sync() could fail, but not attaching the 
> DMA-buf is certainly the best we could do here in that moment.

Ah, I see. Just curious about, before this patch, when we tried to reserve the BO, without the PM sync, how was that doing OK ?

- Shashank

> Otherwise we could end up in accessing the PCIe BAR with power disabled 
> and that's indeed kind of bad.
>
> Christian.
>
>>>>          r = amdgpu_bo_reserve(bo, false);
>>>>          if (unlikely(r != 0))
>>>> -               return r;
>>>> +               goto out;
>>>>
>>>>          /*
>>>>           * We only create shared fences for internal use, but importers
>>>> @@ -201,11 +206,15 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
>>>>           */
>>>>          r = __dma_resv_make_exclusive(bo->tbo.base.resv);
>>>>          if (r)
>>>> -               return r;
>>>> +               goto out;
>>>>
>>>>          bo->prime_shared_count++;
>>>>          amdgpu_bo_unreserve(bo);
>>>>          return 0;
>>>> +
>>>> +out:
>>>> +       pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
>> Why not just pm_runtime_put_sync ? Why autosuspend ?
>>
>> - Shashank
>>
>>>> +       return r;
>>>>   }
>>>>
>>>>   /**
>>>> @@ -225,6 +234,9 @@ static void amdgpu_dma_buf_detach(struct dma_buf *dmabuf,
>>>>
>>>>          if (attach->dev->driver != adev->dev->driver && bo->prime_shared_count)
>>>>                  bo->prime_shared_count--;
>>>> +
>>>> +       pm_runtime_mark_last_busy(adev_to_drm(adev)->dev);
>>>> +       pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
>>>>   }
>>>>
>>>>   /**
>>>> --
>>>> 2.25.4
>>>>
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