amdgpu driver halted on suspend of shutdown

[李真能]

So, Can I remove suspend process in amdgpu_pci_shutdown if  I don't  use 
amdgpu driver in vm?

Thank you so much foryour reply!

在 2021/9/30 上午5:12, Alex Deucher 写道:
> On Wed, Sep 29, 2021 at 3:25 AM 李真能 <lizhenneng at kylinos.cn> wrote:
>> Hello:
>>
>>           When I do loop  auto test of reboot, I found  kernel may halt
>> on memcpy_fromio of amdgpu's amdgpu_uvd_suspend, so I remove suspend
>> process in amdgpu_pci_shutdown, and it will fix this bug.
>>
>> I have 3 questions to ask:
>>
>> 1. In amdgpu_pci_shutdown, the comment explains why we must execute
>> suspend,  so I know VM will call amdgpu driver in which situations, as I
>> know, VM's graphics card is a virtual card;
>>
>> 2. I see a path that is commited by Alex Deucher, the commit message is
>> as follows:
>>
>> drm/amdgpu: just suspend the hw on pci shutdown
>>
>> We can't just reuse pci_remove as there may be userspace still
>>       doing things.
>>
>> My question is:In which situations, there may be  userspace till doing
>> things.
>>
>> 3. Why amdgpu driver is halted on memcpy_fromio of amdgpu_uvd_suspend, I
>> haven't launch any video app during reboot test, is it the bug of pci bus?
>>
>> Test environment:
>>
>> CPU: arm64
> I suspect the problem is something ARM specific.  IIRC, we added the
> memcpy_fromio() to work around a limitation in ARM related to CPU
> mappings of PCI BAR memory.  The whole point of the PCI shutdown
> callback is to put the device into a quiescent state (e.g., stop all
> DMAs and asynchronous engines, etc.).  Some of that tear down requires
> access to PCI BARs.
>
> Alex
>
>
>> Graphics card: r7340(amdgpu), rx550
>>
>> OS: ubuntu 2004
>>
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