[alsa-devel] HDMI hotplug on Skylake when power well is off

[David Henningsson]

On 2015-07-16 10:39, Vinod Koul wrote:
> On Wed, Jul 15, 2015 at 12:59:02PM +0200, Takashi Iwai wrote:
>> On Wed, 15 Jul 2015 11:05:22 +0200,
>> David Henningsson wrote:
>>>
>>> Hi,
>>>
>>> I'm trying to debug an issue here where the HDMI hotplug events are not
>>> delivered to the audio side when the power well is off. This is on a
>>> Skylake machine (running in HDA mode).
>>>
>>> I'm not sure whether the problem is upstream or due to my own patches
>>> while testing, so I was wondering how this is supposed to be working, so
>>> I can troubleshoot further?
>>>
>>> Should there be an IRQ on the HDA controller even if the power well is
>>> off, and if not, how should the audio driver be notified that an HDMI
>>> hotplug event has happened?
>>
>> I thought this has been always a problem when the runtime PM is
>> enabled, no matter whether the power well state is.
> Shouldn't the hotplug action turn on the power well? Then notification for
> audio side should get propagated as power well is On

While the video side can turn the power well on, maybe there are other 
things that needs to be turned on from the audio driver?

>> IMO, a cleaner solution would be rather the notifier implementation in
>> software, e.g. extend the i915 component to pass the audio side ops
>> for notification.
> Yes that should be added but I would prefer we have hw do that as well

So I took a quick stab at this and tried to write down a draft, but I 
got stuck trying to figure out how to wake up the audio codecs from the 
hdac_i915.c file. I'm not sure how to do this with the recent reorg as I 
don't want to break the ASoC version of the driver by including the 
wrong header files.

See attached patch (which is a very rough draft, not even compile 
tested), maybe you or Takashi could offer some insight w r t whether I'm 
on the right track, and how to proceed?

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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