[PATCH 2/2] drm/amdgpu: stop/resume fb access when gpu reset

[Alex Deucher]

On Tue, Jun 21, 2016 at 9:21 AM, Deucher, Alexander
<Alexander.Deucher at amd.com> wrote:
>> -----Original Message-----
>> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf
>> Of Chunming Zhou
>> Sent: Tuesday, June 21, 2016 4:12 AM
>> To: amd-gfx at lists.freedesktop.org
>> Cc: Zhou, David(ChunMing)
>> Subject: [PATCH 2/2] drm/amdgpu: stop/resume fb access when gpu reset
>>
>> Change-Id: I86b5c2b8c78a17ef43ade2a97ef8a33853650be0
>> Signed-off-by: Chunming Zhou <David1.Zhou at amd.com>
>> ---
>>  drivers/gpu/drm/amd/amdgpu/cik.c | 9 +++++++++
>>  drivers/gpu/drm/amd/amdgpu/vi.c  | 8 +++++++-
>>  2 files changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/cik.c
>> b/drivers/gpu/drm/amd/amdgpu/cik.c
>> index 40f4fda..716efa8 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/cik.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/cik.c
>> @@ -1213,10 +1213,19 @@ static void
>> cik_set_bios_scratch_engine_hung(struct amdgpu_device *adev, bool hu
>>  static int cik_asic_reset(struct amdgpu_device *adev)
>>  {
>>       int r;
>> +     struct amdgpu_mode_mc_save save;
>> +
>>       cik_set_bios_scratch_engine_hung(adev, true);
>> +     /* Disable fb access */
>> +     if (adev->mode_info.num_crtc)
>> +             amdgpu_display_stop_mc_access(adev, &save);
>
> You don't need to check if there are crtcs or not before stopping the mc.  The stop_mc_access and resume_mc_access callbacks will handle that automatically.  Also on chips with no DCE hardware, you still want to stop the mc.  Same for vi.c.

Nevermind, I was thinking of the actual gmc stop/resume mc functions.
So the code here with the num_crtc check is correct with respect to
disabling mc access in the dce block.  However, why do we need this?
The mc_stop sort of makes sense, but resuming after the reset doesn't
since the gpu state is reset after the reset so what's the point?
Wouldn't this already be taken care of by the ip specific suspend and
resume functions (e.g., gmc resume)?

Alex

>
> Alex
>
>>
>>       r = cik_gpu_pci_config_reset(adev);
>>
>> +     /* resume fb access */
>> +     if (adev->mode_info.num_crtc)
>> +             amdgpu_display_resume_mc_access(adev, &save);
>> +
>>       cik_set_bios_scratch_engine_hung(adev, false);
>>
>>       return r;
>> diff --git a/drivers/gpu/drm/amd/amdgpu/vi.c
>> b/drivers/gpu/drm/amd/amdgpu/vi.c
>> index 1ac0c91..497b817 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/vi.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/vi.c
>> @@ -633,10 +633,16 @@ static void vi_set_bios_scratch_engine_hung(struct
>> amdgpu_device *adev, bool hun
>>  static int vi_asic_reset(struct amdgpu_device *adev)
>>  {
>>       int r;
>> +     struct amdgpu_mode_mc_save save;
>>
>>       vi_set_bios_scratch_engine_hung(adev, true);
>> -
>> +     /* Disable fb access */
>> +     if (adev->mode_info.num_crtc)
>> +             amdgpu_display_stop_mc_access(adev, &save);
>>       r = vi_gpu_pci_config_reset(adev);
>> +     /* resume fb access */
>> +     if (adev->mode_info.num_crtc)
>> +             amdgpu_display_resume_mc_access(adev, &save);
>>
>>       vi_set_bios_scratch_engine_hung(adev, false);
>>
>> --
>> 1.9.1
>>
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