[alsa-devel] [PATCH] ASoC: Intel: Power down links before turning off display audio power

[Takashi Iwai]

On Mon, 25 Jun 2018 10:53:49 +0200,
Sriram Periyasamy wrote:
> 
> On Fri, Jun 22, 2018 at 07:14:50PM +0200, Takashi Iwai wrote:
> > On Fri, 22 Jun 2018 18:42:24 +0200,
> > Pierre-Louis Bossart wrote:
> > > 
> > > On 6/22/18 4:25 AM, Sriram Periyasamy wrote:
> > > > On certain platforms, Display HDMI HDA codec was not going to sleep state
> > > > after the use when links are powered down after turning off the display
> > > > power. As per the HW recommendation, links are powered down before turning
> > > > off the display power to ensure that the codec goes to sleep state.
> > > 
> > > The change looks ok, I am still not clear on display power
> > > management. snd_hdac_display_power is called both from hdac_hdmi.c and
> > > skl.c in the respective probe/suspend/resume routines, wondering if
> > > this is redundant or intentional.
> > 
> > Yeah, it looks like that skl.c keeps the display power on by assuming
> > that it's turned off by the codec driver, but it doesn't happen
> > actually.  I also find it fishy there...
> > 
> 
> snd_hdac_display_power is called intentionally to ensure that the codec is
> powered up before any communication is initiated from either skl.c or
> hdac_hdmi.c.

But who turns it down if the device is not used?
It'd be helpful if you can illustrate the PM scheme in a big picture.


thanks,

Takashi