[Applied][Raring PATCH] Ubuntu (no-up): ALSA: hda - fixup D3 pin and right channel mute on Haswell HDMI audio

[David Henningsson]

On 04/11/2013 04:31 PM, Tim Gardner wrote:
> On 04/11/2013 07:28 AM, Leann Ogasawara wrote:
>> On 04/11/2013 06:09 AM, Leann Ogasawara wrote:
>>> Applied to Raring master-next.
>>
>> Hi David,
>>
>> After I'd applied this to Raring master-next, there was some concern
>> raised about the patch via the #ubuntu-kernel IRC channel.  We are
>> hoping to get some clarification and feedback from you.
>>
>> [06:12:36] <rtg_> ogasawara, actually, I was gonna question David on
>> that patch. it seems over engineered to me.
>> [06:14:13] <ogasawara> rtg_: I thought it seemed fairly well contained
>> and tested
>> [06:14:40] <ogasawara> rtg_: it's not too late to yank it if you have
>> reservations
>> [06:15:12] <rtg_> ogasawara, in that it only affects haswell. however,
>> why not just force the D0 and mute settings rather then interrogate the
>> HW ? less code I think.
>> [06:17:24] <ogasawara> rtg_: it's a valid question, want me to punt it
>> till we get clarification?
>> [06:18:54] <rtg_> ogasawara, if we can get ahold of him today.
>> [06:20:23] <rtg_> ogasawara, by collapsing the code into a more
>> definitive form I might worry about audio artifacts such as pops and
>> clicks whilst programming those registers. thats really what I'd like to
>> confirm from him.
>>
>>>
>>> On 04/11/2013 12:38 AM, David Henningsson wrote:
>>>> BugLink: https://bugs.launchpad.net/bugs/1167270
>>>>
>>>> This patch has been tested on two machines, and found to resolve one
>>>> of the HDMI audio issues on Haswell.
>>>>
>>>> The root cause is lack of synchronisation between the video driver and
>>>> the audio driver. Upstream wants to resolve this by adding
>>>> synchronisation mechanisms, so they won't take this patch. But since
>>>> kernel freeze is today, I wanted to ask you to accept this
>>>> intermediate workaround, which at every playback start checks for the
>>>> error and corrects it if found.
>>>>
>>>>
>>>>
>>>>
>>>
>>
>
> Perhaps something like the attached.
>

Thanks for the review.

There are two things here: The D0 and the mute.

For the D0 part, I *think* setting it always is harmless and shouldn't 
cause any clicks or similar. After all, this is a digital connection so 
artifacts should be avoided by the recipient (HDMI monitor/receiver) anyway.
The gain to keep it as it is would be to avoid the 40 ms delay in case 
this does not happen (which is does not in the majority of cases). But 
probably just enabling it, skipping the delay, and not read it back for 
debugging would work too, I just haven't tested it (and can't do so 
since the hw is in Asia), and I know you like patches to be tested 
before you apply them :-)

For the mute part; I think the patch suggested by rtg is buggy since it 
always enables audio, without taking the mute kcontrol into affect: 
there is a "IEC958 Playback Switch" control that user could set to turn 
both channels off legitimately. So the mute part needs to stay the way 
it was in my version of the patch.



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