On Fri, 2021-01-22 at 15:12 +0100, Takashi Iwai wrote: > On Fri, 22 Jan 2021 00:23:53 +0100, > Ranjani Sridharan wrote: > > Hi Takashi, > > > > While exploring some power optimizations on Intel platforms, I > > noticed > > that the hdac_ext_link ref_count is incremented during codec probe > > in hdac_hda_codec_probe() and the ref_count is held until the codec > > device is removed. > > > > I was wondering if it would be possible to call the get/put for the > > hdac_ext_link in the codec runtime suspend/resume callbacks so that > > the > > link is powered up only when the link is in use. Are there any > > downsides to doing this? > > Wouldn't the snd_hdac_ext_bus_link_power_up() / down() calls do the > runtime PM stuff? Maybe we need to revisit those link power > management. The ext stuff isn't well m > and, I'm afraid. Thanks, Takashi. It looks like snd_hdac_ext_bus_link_power_up/down() are only called during snd_hdac_ext_bus_link_get/put(). Actually, in my observation disabling the CORB/RIRB buffer DMAs is what saves us power and this is done only if snd_hdac_ext_bus_link_put() is called on all links. > > The get() and put() are obviously for fully enabling and disabling > the > device, hence it's not suitable for the runtime PM suspend/resume. > The power_up() / down() should be adjusted to fit with the runtime PM > call, if any. The only additional thing that snd_hdac_ext_bus_link_get/put() does on top of snd_hdac_ext_bus_link_power_up/down() is to stop the CORB/RIRB DMA when all the link ref_counts are 0. Do you think it is not advisable to stop the CORB/RIRB DMA during runtime PM? Thanks, Ranjani
