[PATCH] ALSA: hda: enable the runtime_pm for non-vgaswitcheroo hda controllers

[Roy Spliet]

Op 14-04-2020 om 13:56 schreef Hui Wang:
> 
> On 2020/4/14 下午8:42, Roy Spliet wrote:
>> Dear Hui, Takashi,
>>
>> Op 14-04-2020 om 13:35 schreef Hui Wang:
>>>
>>> On 2020/4/14 下午6:27, Takashi Iwai wrote:
>>>> On Tue, 14 Apr 2020 12:14:05 +0200,
>>>> Hui Wang wrote:
>>>>> Before the pci_driver->probe() is called, the pci subsystem calls
>>>>> runtime_forbib() and runtime_get_sync() on this pci dev, so only call
>>>>> runtime_put_autosuspend() is not enough to enable the runtime_pm on
>>>>> this device.
>>>>>
>>>>> For controllers with vgaswitcheroo feature, the pci/quirks.c will call
>>>>> runtime_allow() for this dev, then the controllers could enter
>>>>> rt_idle/suspend/resume, but for non-vgaswitcheroo controllers like
>>>>> Intel hda controllers, the runtime_pm is not enabled even it calls
>>>>> put_autosuspend(). Need to call runtime_allow() for those controllers
>>>>> in the hda driver.
>>
>> From what I can tell there are no ill effects of calling 
>> runtime_allow() twice. Technically, the check against 
>> use_vga_switcheroo() is thus redundant.
>> Is there a good reason why runtime_allow() is called in the pci quirks 
>> rather than in hda_intel? Is it a suggestion to perform this call in 
>> hda_intel regardless of whether it's a switcheroo-device or not, and 
>> removing calls to runtime_allow() from the PCI quirks?
> 
> I guess after the hda driver calls the _allow() unconditionally, we 
> could remove the _allow() in the pci/quirks.c. But it is no harm keeping 
> it since _allow() could be called many times.

After a bit of research, I agree! It's better left in place in the PCI 
quirks, such that in the case that hda_intel doesn't load or bind for 
whatever reason (not compiled in e.g. an embedded kernel, new/unknown 
PCI vendor/device identifier), the GPUs HDA device can still run-time 
suspend.
Thank you! Best,

Roy

> 
> Thanks,
> 
> Hui.
> 
>> Thanks. Best,
>>
>> Roy
>>>>>
>>>>> Signed-off-by: Hui Wang <hui.wang at canonical.com>
>>>> Was this behavior changed from the earlier kernels?  I thought this
>>>> was left untouched because it's supposed to be set via udev rules or
>>>> such.
>>>
>>> Oh, I don't know that,  according to my test with ubuntu rootfs, the 
>>> runtime pm is not enabled on Intel's hda controllers. But with the 
>>> sof driver, the controller driver calls runtime_allow() 
>>> (soc/sof/sof-pci-dev.c), so I sent this patch.
>>>
>>> Regards,
>>>
>>> Hui.
>>>
>>>> OTOH, enabling the runtime PM is almost mandatory for modern systems,
>>>> and I'm fine to apply this kind of forcible enablement.
>>>>
>>>>
>>>> thanks,
>>>>
>>>> Takashi
>>>>
>>>>
>>>>> ---
>>>>>   sound/pci/hda/hda_intel.c | 2 ++
>>>>>   1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
>>>>> index 8519051a426e..779705bef88b 100644
>>>>> --- a/sound/pci/hda/hda_intel.c
>>>>> +++ b/sound/pci/hda/hda_intel.c
>>>>> @@ -2356,6 +2356,8 @@ static int azx_probe_continue(struct azx *chip)
>>>>>       if (azx_has_pm_runtime(chip)) {
>>>>>           pm_runtime_use_autosuspend(&pci->dev);
>>>>> +        if (!use_vga_switcheroo(chip))
>>>>> +            pm_runtime_allow(&pci->dev);
>>>>>           pm_runtime_put_autosuspend(&pci->dev);
>>>>>       }
>>>>> -- 
>>>>> 2.17.1
>>>>>