Re: [PATCH] vgaswitchroo: set audio client id according to bound gpu client id

[Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>]

On Mon, Jul 09, 2018 at 08:52:33AM +0000, Qu, Jim wrote:
> Now, I found the audio device will auto suspend even if the gpu is active,
> and if I plug in a HDMI device it also do not resume back. 
> 
> 1. Did you encounter similar issue before?
> 2. audio will auto suspend as default at beginning of boot, is it expect
> behaviour?

Yes, that's expected.  Once you start streaming audio to attached displays,
user space opens the codec device and this causes the HDA controller to
runtime resume.  If the discrete GPU is suspended at that moment, it will
be powered on and kept powered on as long as user space is streaming audio.

Do you need to runtime resume the HDA controller even if user space isn't
streaming audio?  Why, and in which situation exactly?

You're saying above that the HDA controller isn't runtime resumed on
hotplug of a display.  Is that necessary to retrieve ELD or something?
I'm not sure if there's code in the HDA driver to acquire a runtime PM
ref on HPD, but maybe it's necessary.  Or maybe the code is there but
somehow no HPD interrupt is received by the HDA driver?

Thanks,

Lukas
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