Re: [PATCH v2 3/3] drm/amdgpu: Warn about disabled DPM

["Christian König" <christian.koenig@amd.com>]

Am 22.06.20 um 19:25 schrieb Paul Menzel:
> Dear Christian,
>
>
> Am 22.06.20 um 15:39 schrieb Christian König:
>> Am 19.06.20 um 20:50 schrieb Paul Menzel:
>>> Currently, besides there is no explicit message, that DPM is disabled.
>>> The user would need to know, that the missing success line indicates
>>> that.
>>>
>>>      [drm] amdgpu: dpm initialized
>>>
>>> So, add an explicit message, and make it log level warning, as 
>>> disabling
>>> dpm is not the default, and device performance will most likely suffer.
>>>
>>> Resolves: 
>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1173&data=02%7C01%7Cchristian.koenig%40amd.com%7C72d0b71d439e46d6253f08d816d150c6%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637284435558396492&sdata=5EXY1o1zwXJRzN9fqpUg%2BQNJGB3zAlWKnGWsdFXRcjA%3D&reserved=0 
>>
>
> That URL is not mine. ;-)
>
>>> Cc: amd-gfx@lists.freedesktop.org
>>> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
>>> ---
>>> v2: Use new print helpers, and inform user about effects.
>>>
>>>   drivers/gpu/drm/amd/amdgpu/kv_dpm.c | 4 +++-
>>>   drivers/gpu/drm/amd/amdgpu/si_dpm.c | 4 +++-
>>>   2 files changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/kv_dpm.c 
>>> b/drivers/gpu/drm/amd/amdgpu/kv_dpm.c
>>> index f054ded902f2..c601587c6d59 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/kv_dpm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/kv_dpm.c
>>> @@ -3014,8 +3014,10 @@ static int kv_dpm_sw_init(void *handle)
>>>       adev->pm.current_mclk = adev->clock.default_mclk;
>>>       adev->pm.int_thermal_type = THERMAL_TYPE_NONE;
>>> -    if (amdgpu_dpm == 0)
>>> +    if (amdgpu_dpm == 0) {
>>> +        drm_warn(adev, "amdgpu: dpm disabled per parameter. Your 
>>> graphics device will run with lower clocks impacting graphics 
>>> performance.\n");
>>
>> I'm not very keen about this. When an user specifies that DPM 
>> shouldn't be used the driver doesn't need to inform the user about 
>> this once more.
>>
>> In other words shooting in your own foot is supposed to hurt.
>
> Maybe. The other point of view is, how does having the clarity in the 
> logs hurt?

Well, you are spamming the logs with a warning about an intentional 
behavior.

> For example, if the user added the parameter intentionally, maybe they 
> made a typo, and it’s actually not applied. Or there is a bug in the 
> parameter handling. Having explicit log messages is good in my opinion.
>
> Secondly, the parameter could have been left there unintentionally. 
> Having the message in the logs, makes the user aware of tha.

And exactly for this reason the kernel command line is printed as the 
second line of the logs.

Duplicating this in each driver is not only overkill, but also very 
error prone.

Sorry, but this is absolutely don't think that this is a good idea.

Regards,
Christian.

>
>
> Kind regards,
>
> Paul
>
>
>>>           return 0;
>>> +    }
>>>       INIT_WORK(&adev->pm.dpm.thermal.work, 
>>> amdgpu_dpm_thermal_work_handler);
>>>       mutex_lock(&adev->pm.mutex);
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/si_dpm.c 
>>> b/drivers/gpu/drm/amd/amdgpu/si_dpm.c
>>> index f7edc1d50df4..1f35d5a36300 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/si_dpm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/si_dpm.c
>>> @@ -7687,8 +7687,10 @@ static int si_dpm_sw_init(void *handle)
>>>       adev->pm.current_mclk = adev->clock.default_mclk;
>>>       adev->pm.int_thermal_type = THERMAL_TYPE_NONE;
>>> -    if (amdgpu_dpm == 0)
>>> +    if (amdgpu_dpm == 0) {
>>> +        drm_warn(adev, "amdgpu: dpm disabled per parameter. Your 
>>> graphics device will run with lower clocks impacting graphics 
>>> performance.\n");
>>>           return 0;
>>> +    }
>>>       ret = si_dpm_init_microcode(adev);
>>>       if (ret)
>>

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