[PATCH 2/2] drm/amdgpu: enable DPM_FLAG_MAY_SKIP_RESUME and DPM_FLAG_SMART_SUSPEND flags

[Bhardwaj, Rajneesh]

On 2/4/2021 10:14 AM, Felix Kuehling wrote:
> Am 2021-02-04 um 9:37 a.m. schrieb Alex Deucher:
>> On Wed, Feb 3, 2021 at 2:56 AM Lazar, Lijo <Lijo.Lazar at amd.com> wrote:
>>> [AMD Public Use]
>>>
>>>
>>> -----Original Message-----
>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Alex Deucher
>>> Sent: Tuesday, February 2, 2021 10:48 PM
>>> To: amd-gfx at lists.freedesktop.org
>>> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>
>>> Subject: [PATCH 2/2] drm/amdgpu: enable DPM_FLAG_MAY_SKIP_RESUME and DPM_FLAG_SMART_SUSPEND flags
>>>
>>> Once the device has runtime suspended, we don't need to power it back up again for system suspend.  Likewise for resume, we don't to power up the device again on resume only to power it back off again via runtime pm because it's still idle.
>>>
>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 6 ++++++
>>>   1 file changed, 6 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>> index b4780182f990..b78847fa769b 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>> @@ -206,6 +206,12 @@ int amdgpu_driver_load_kms(struct amdgpu_device *adev, unsigned long flags)
>>>                  if (amdgpu_device_supports_atpx(dev) &&
>>>                      !amdgpu_is_atpx_hybrid())
>>>                          dev_pm_set_driver_flags(dev->dev, DPM_FLAG_NO_DIRECT_COMPLETE);
>>> +               /* we want direct complete for BOCO */
>>> +               if ((amdgpu_device_supports_atpx(dev) &&
>>> +                   amdgpu_is_atpx_hybrid()) ||
>>> +                   amdgpu_device_supports_boco(dev))
>>> +                       dev_pm_set_driver_flags(dev->dev, DPM_FLAG_SMART_SUSPEND |
>>> +                                               DPM_FLAG_MAY_SKIP_RESUME);
>>>
>>> Device runtime suspend callback does -
>>>          amdgpu_device_suspend(drm_dev, false)
>>>
>>> System suspend callback does -
>>>          amdgpu_device_suspend(drm_dev, true)
>>>
>>> One of the effects of this flag is for KFD to decide whether to evict all processes. It is done during system suspend but not during runtime device suspend. Will that have an impact if  the system suspend routine is skipped in this way?
>> + Rajneesh
>>
>> Can you comment on this?  Idea of this patch is to not wake the device
>> for system suspend and resume if it's already in runtime suspend.

KFD doesn't allow amdgpu driver to runtime suspend the device as long as 
the per process device data is valid. This patch only enables direct 
complete path for already runtime suspended amdgpu device so its 
implicit that kfd had no active process. While we may be OK to not 
explicitly cancel scheduled work or suspend all kfd processes (since gpu 
is already runtime suspended) we still leave KFD unlocked for a system 
wide suspend via direct complete path.  I think we should still be ok 
with this since locking is only used for making sure that kfd is not 
open during a gpu reset.

Also i suggest using DPM_FLAG_SMART_PREPARE as well, since we are 
relying on prepare for skipping late/noirq phase during system suspend.


Acked-by: Rajneesh Bhardwaj <rajneesh.bhardwaj at amd.com>


> KFD only allows runtime suspend when there are no processes using the
> GPU. Therefore it should be safe (in theory) to skip process eviction if
> you're already in runtime suspend. Just make sure all the suspend/resume
> calls into KFD are paired up correctly. If you skip suspend but then
> later call resume anyway, it will likely cause problems.
>
> For testing this, I'd suggest running some KFD application (e.g. kfdtest
> or an OpenCL app with ROCm-based OpenCL) before suspend, then suspend,
> then run the app again after resume to make sure KFD is still good.
>
> Regards,
>    Felix
>
>
>> Alex
>>
>>> Thanks,
>>> Lijo
>>>
>>>                  pm_runtime_use_autosuspend(dev->dev);
>>>                  pm_runtime_set_autosuspend_delay(dev->dev, 5000);
>>>                  pm_runtime_allow(dev->dev);
>>> --
>>> 2.29.2
>>>
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>>> amd-gfx mailing list
>>> amd-gfx at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
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