On Mon, 06 Jul 2020 22:53:17 +0200, Harsha Priya wrote: > > External HDMI receivers have analog circuitry that needs to be powered-on > when exiting standby, and a mechanism to detect PCM v. IEC61937 data. > These two steps take time and up to 2-3 seconds of audio may be muted > when starting playback. > > Intel hardware (Haswell and beyond) can keep the link active > with a 'silent stream', so that the receiver does not go through those > two steps when valid audio is transmitted. This mechanism relies > on an setting the channel_id as 0xf, sending info packet and preventing > the codec from going to D3, which will increase the platform > static power consumption. The info packet assumes a basic 2ch stereo, > and the silent stream is enabled when connecting a monitor. > In case of format changes the detection of PCM v. IEC61937 needs to > be re-run. In this case there is no way to avoid the 2-3s mute. > > The silent stream is enabled with a Kconfig option, as well as a kernel > parameter should there be a need to override the build time default. > This approach is used based on the power_save capability as an example, > but in the future, it may be used with a kcontrol, > depending on UCM support for HDaudio legacy. > > Signed-off-by: Harsha Priya <harshapriya.n@xxxxxxxxx> > Signed-off-by: Emmanuel Jillela <emmanuel.jillela@xxxxxxxxx> > Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx> > Reported-by: kernel test robot <lkp@xxxxxxxxx> Applied now to for-next branch. Thanks. Takashi
