[PATCH] drm/amdgpu/vcn1: add cancel_delayed_work_sync before power gate

[Christian König]

Am 18.05.21 um 17:59 schrieb James Zhu:
>
> On 2021-05-18 11:54 a.m., Christian König wrote:
>>
>>
>> Am 18.05.21 um 17:45 schrieb James Zhu:
>>>
>>> On 2021-05-18 11:23 a.m., Christian König wrote:
>>>> Am 18.05.21 um 17:11 schrieb James Zhu:
>>>>> Add cancel_delayed_work_sync before set power gating state
>>>>> to avoid race condition issue when power gating.
>>>>>
>>>>> Signed-off-by: James Zhu <James.Zhu at amd.com>
>>>>> ---
>>>>>   drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c | 19 ++++++++++++++++++-
>>>>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c 
>>>>> b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
>>>>> index 0c1beef..6c5c083 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
>>>>> @@ -230,10 +230,27 @@ static int vcn_v1_0_hw_init(void *handle)
>>>>>   static int vcn_v1_0_hw_fini(void *handle)
>>>>>   {
>>>>>       struct amdgpu_device *adev = (struct amdgpu_device *)handle;
>>>>> +    struct amdgpu_ring *ring;
>>>>> +    int i;
>>>>> +
>>>>> +    ring = &adev->vcn.inst->ring_dec;
>>>>> +    ring->sched.ready = false;
>>>>> +
>>>>> +    for (i = 0; i < adev->vcn.num_enc_rings; ++i) {
>>>>> +        ring = &adev->vcn.inst->ring_enc[i];
>>>>> +        ring->sched.ready = false;
>>>>> +    }
>>>>> +
>>>>> +    ring = &adev->jpeg.inst->ring_dec;
>>>>> +    ring->sched.ready = false;
>>>>
>>>> Thinking more about that this is a really big NAK. The scheduler 
>>>> threads must to stay ready during a reset.
>>>>
>>>> This is controlled by the upper layer and shouldn't be messed with 
>>>> in the hardware specific backend at all.
>>>
>>>> [JZ] I ported this from current vcn3 hw_fini. Just want to make 
>>>> sure that no more new jobs will be scheduled after suspend process 
>>>> starts.
>>> It may a redundancy, since scheduler maybe already suspend. I can 
>>> remove those if you are sure no side effect,
>>
>> Well, we *must* remove those. This flag controls if the hardware 
>> engine can be used for command submission and is only be set to 
>> true/false during initial driver load.
>>
>> If you change it to false during hw_fini the engine won't work 
>> correctly any more after GPU reset or resume.
> [JZ] If I recalled correctly tat hw_init will be called every time 
> after GPU reset or suspend/resume,

Yes that's correct.

But before that and during GPU reset the ready flag is then false for a 
short period of time which would result in userspace applications 
crashing when they try to submit something.

The flag essentially says that userspace can submit jobs to the 
scheduler. Processing of those jobs is of course only started after the 
hardware is re-initialized, but pushing jobs down the pipe is still 
perfectly valid in that situation.

Christian.

>>
>> If you have any idea how to document that fact then please speak up, 
>> cause we had this problem a couple of times now.
>>
>> Just send out a patch fixing various other occasions of that.
>>
>> Regards,
>> Christian.
>>
>>>
>>>> I've removed all of those a couple of years ago.
>>>>
>>>> Regards,
>>>> Christian.
>>>>
>>>>> +
>>>>> + cancel_delayed_work_sync(&adev->vcn.idle_work);
>>>>>         if ((adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG) ||
>>>>> -        RREG32_SOC15(VCN, 0, mmUVD_STATUS))
>>>>> +        (adev->vcn.cur_state != AMD_PG_STATE_GATE &&
>>>>> +         RREG32_SOC15(VCN, 0, mmUVD_STATUS))) {
>>>>>           vcn_v1_0_set_powergating_state(adev, AMD_PG_STATE_GATE);
>>>>> +    }
>>>>>         return 0;
>>>>>   }
>>>>
>>