Changing snd_hda_intel.power_save default value ?

Changing snd_hda_intel.power_save default value ?

[Hans de Goede]

Hi All,

I'm working on trying to improve the OOTB power-consumption
of Linux (Fedora Workstation) on laptops.

One of the easy wins here is setting snd_hda_intel.power_save=1

I see that the default is configurable through a Kconfig option,
currently Fedora is using the Kconfig default value of 0.

So I'm wondering if there any known issues with changing the
default to 1 ?

I was also thinking that maybe an automatic value
(SND_HDA_POWER_SAVE_DEFAULT == -1) might be a good idea,
which would mean 0 normally except for PCI-ids which are
markes with a MOBILE flag in their driver_data in
the azx_ids pci_device_id table ?

Regards,

Hans

Re: Changing snd_hda_intel.power_save default value ?

[Takashi Iwai]

On Wed, 01 Nov 2017 15:19:44 +0100,
Hans de Goede wrote:
> 
> Hi All,
> 
> I'm working on trying to improve the OOTB power-consumption
> of Linux (Fedora Workstation) on laptops.
> 
> One of the easy wins here is setting snd_hda_intel.power_save=1
> 
> I see that the default is configurable through a Kconfig option,
> currently Fedora is using the Kconfig default value of 0.
> 
> So I'm wondering if there any known issues with changing the
> default to 1 ?

This may bring click noises on some laptops or desktops, but it should
be OK for the functionalities.  On openSUSE Tumbleweed kernels, we
already pass 1 for some time.  Some reports came up occasionally but
they can work around by setting the module option.

> I was also thinking that maybe an automatic value
> (SND_HDA_POWER_SAVE_DEFAULT == -1) might be a good idea,
> which would mean 0 normally except for PCI-ids which are
> markes with a MOBILE flag in their driver_data in
> the azx_ids pci_device_id table ?

I'm afraid that it'd be hard to manage that table.  This is one of
mostly modified module option, e.g. a power-management daemon often
adjusts the value dynamically.
So, for modern distros, feel free simply set to value 1, but I see no
reason to hustle for changing kconfig default value in the tree.  For
the default value, we want to be conservative in general.


thanks,

Takashi

Re: Changing snd_hda_intel.power_save default value ?

[Hans de Goede]

Hi,

On 01-11-17 17:54, Takashi Iwai wrote:
> On Wed, 01 Nov 2017 15:19:44 +0100,
> Hans de Goede wrote:
>>
>> Hi All,
>>
>> I'm working on trying to improve the OOTB power-consumption
>> of Linux (Fedora Workstation) on laptops.
>>
>> One of the easy wins here is setting snd_hda_intel.power_save=1
>>
>> I see that the default is configurable through a Kconfig option,
>> currently Fedora is using the Kconfig default value of 0.
>>
>> So I'm wondering if there any known issues with changing the
>> default to 1 ?
> 
> This may bring click noises on some laptops or desktops, but it should
> be OK for the functionalities.  On openSUSE Tumbleweed kernels, we
> already pass 1 for some time.  Some reports came up occasionally but
> they can work around by setting the module option.
> 
>> I was also thinking that maybe an automatic value
>> (SND_HDA_POWER_SAVE_DEFAULT == -1) might be a good idea,
>> which would mean 0 normally except for PCI-ids which are
>> markes with a MOBILE flag in their driver_data in
>> the azx_ids pci_device_id table ?
> 
> I'm afraid that it'd be hard to manage that table.  This is one of
> mostly modified module option, e.g. a power-management daemon often
> adjusts the value dynamically.
> So, for modern distros, feel free simply set to value 1, but I see no
> reason to hustle for changing kconfig default value in the tree.  For
> the default value, we want to be conservative in general.

Ok, I will discuss changing the Kconfig option to "1" with the
Fedora kernel team.

Thanks & Regards,

Hans