Re: Changing snd_hda_intel.power_save default value ?

[Takashi Iwai <tiwai@suse.de>]

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