[PATCH] drm/amdgpu:No action needs when VCN PG state is unchanged

[James Zhu]

On 2018-09-11 11:17 AM, Christian König wrote:
> Am 11.09.2018 um 17:06 schrieb James Zhu:
>>
>>
>>
>> On 2018-09-11 10:44 AM, Alex Deucher wrote:
>>> On Mon, Sep 10, 2018 at 4:34 PM James Zhu<jzhums at gmail.com>  wrote:
>>>> Signed-off-by: James Zhu<James.Zhu at amd.com>
>>>>
>>>> When VCN PG state is unchanged, it is unnecessary to reset
>>>> power gate state again.
>>> Don't you need to initialize and store the PG state somewhere?  You
>>> are just using a local variable here.
>>>
>>> Alex
>>>
>> Hi Alex,
>>
>> I used */static/* for this local state variable(*cur_state*) with 
>> initialization state AMD_PG_STATE_GATE.
>
> That won't work correctly. A "static" variable is global, but the 
> power state is per device.
>
> Regards,
> Christian.
>
This "static" variable under local scope is mainly for VCN used only. It 
only tracks VCN's PG state.
(currently VCN only have one hardware instance)

Best Regards!
James Zhu
>> this variable's scope is only inside this function, but it's 
>> initialization is done
>> once at compile time and it's lifetime will last until the driver exit.
>>
>> Since it is only used inside this function, I didn't put it into 
>> struct amdgpu_vcn.
>>
>> Best Regards!
>> James Zhu
>>>> ---
>>>>   drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c | 13 +++++++++++--
>>>>   1 file changed, 11 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
>>>> index 2664bb2..86d98d2 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
>>>> @@ -1633,12 +1633,21 @@ static int vcn_v1_0_set_powergating_state(void *handle,
>>>>           * revisit this when there is a cleaner line between
>>>>           * the smc and the hw blocks
>>>>           */
>>>> +       int ret;
>>>> +       static enum amd_powergating_state cur_state = AMD_PG_STATE_GATE;
>>>>          struct amdgpu_device *adev = (struct amdgpu_device *)handle;
>>>>
>>>> +       if (state == cur_state)
>>>> +               return 0;
>>>> +
>>>>          if (state == AMD_PG_STATE_GATE)
>>>> -               return vcn_v1_0_stop(adev);
>>>> +               ret = vcn_v1_0_stop(adev);
>>>>          else
>>>> -               return vcn_v1_0_start(adev);
>>>> +               ret = vcn_v1_0_start(adev);
>>>> +
>>>> +       if (!ret)
>>>> +               cur_state = state;
>>>> +       return ret;
>>>>   }
>>>>
>>>>   static const struct amd_ip_funcs vcn_v1_0_ip_funcs = {
>>>> --
>>>> 2.7.4
>>>>
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>>
>>
>>
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