[PATCH v4 2/2] drm/amd: Add Suspend/Hibernate notification callback support

[Mario Limonciello]

>>> Based on https://gitlab.freedesktop.org/drm/amd/-/issues/3781
>>>
>>> What if this callback takes care only of suspend case and leaves the
>>> hibernate case to dpm_prepare callback?
>>
>> Then hibernate would fail under memory pressure.
>>
>> My take is this failure with hibernate is a userspace problem (whether
>> userspace decides to freeze the tasks or not).  I think it's better that
>> we /try/ to do the eviction and notify them if userspace should be changed.
>>
> 
> Hmm, the logic is kind of inconsistent now.
> 
> For dGPUs, evict is required for s0ix, s3, s4 and attempted twice.
> For APUs, evict is required for s4, but attempted only once.

Well the logic was inconsistent before already.

But FWIW it will still be attempted a second time for APUs.
The call sequence is:

1) PM notifier
amdgpu_device_pm_notifier()
->amdgpu_device_evict_resources()

Eviction for dGPU and APU in S4.

2) Prepare callback
amdgpu_pmops_prepare()
->amdgpu_device_prepare()
->->amdgpu_device_evict_resources()

Eviction for dGPU only.

3) Suspend callback
amdgpu_pmops_freeze()
->amdgpu_device_suspend()
->->amdgpu_device_evict_resources()

Eviction for dGPU and APU in S4.

So yes it's incongruent that prepare() doesn't include APU S4, but the 
problem is you won't know at prepare() time whether it's S4 AFAICT.

Or is there way to tell at prepare() for S4?

> 
> Thanks,
> Lijo
> 
>>>
>>> Thanks,
>>> Lijo
>>>> +    case PM_SUSPEND_PREPARE:
>>>> +        r = amdgpu_device_evict_resources(adev);
>>>> +        adev->in_s4 = false;
>>>> +        /*
>>>> +         * This is considered non-fatal at thie time because
>>>> +         * amdgpu_device_prepare() will also evict resources.
>>>> +         * See https://gitlab.freedesktop.org/drm/amd/-/issues/3781
>>>> +         */
>>>> +        if (r)
>>>> +            drm_warn(adev_to_drm(adev), "Failed to evict resources,
>>>> freeze active processes if problems occur\n");
>>>> +        break;
>>>> +    }
>>>> +
>>>> +    return NOTIFY_DONE;
>>>> +}
>>>> +
>>>>    /**
>>>>     * amdgpu_device_prepare - prepare for device suspend
>>>>     *
>>>
>>
>