On Fri, 22 Jan 2021 17:40:55 +0100, Ranjani Sridharan wrote:
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?
Why do you need to stop CORB/RIRB? For stopping the CORB/RIRB DMA, you need to disable the IRQ and other stuff at first, in anyway.
Takashi