[alsa-devel] DP MST audio support

[Dave Airlie]

On 12 May 2015 at 13:27, Dave Airlie <airlied at gmail.com> wrote:
> On 12 May 2015 at 11:50, Dave Airlie <airlied at gmail.com> wrote:
>> Hi,
>>
>> So I have a branch that makes no sound,
>> http://cgit.freedesktop.org/~airlied/linux/log/?h=dp-mst-audio
>>
>> and I'm not sure where I need to turn to next,
>>
>> The Intel docs I've read are kinda vague, assuming you know lots of
>> things I clearly don't.
>>
>> so in theory my branch, sets up the SDP stream to the monitor in the
>> payload creation,
>> enables the codec in the intel GPU driver, and passes the ELD to the
>> audio driver.
>>
>> The audio driver uses the device list to get the presence/valid bits
>> per device, and manages to retrieve the ELD. I even create ELD files
>> in /proc/asound/HDMI/ that have sensible values in them
>>
>> So it looks like I'm just missing some routing somewhere, most likely
>> in the audio driver, then again I  could be missing a lot more than
>> that.
>>
>> Just looking for any ideas or knowledge people may have locked in
>> their brains or inside their firewalls.
>
> Okay the branch now has audio on my test setup,
>
> I've had to hack out the intel_not_share_assigned_cvt function
> it appears to do bad things, I set pin 6 to connection 0 (pin 2), the later
> sets on pin 5/7 to connection 1 by that function seems to reprogram pin 6.
>
> I'm guessing the connection is assigned to a device not a pin in the new hw,
> and the same device is routed via pin 5/7 so I end up trashing it.
>
> my test setup is a Haswell Lenovo t440s + docking station + Dell U2410.
>

ping audio guys?

can someone from alsa please take a look or some interest in this?

The graphics side patches are fairly trivial, also it would be good to
get a good explaination of how the hw works,

from what I can see devices get connections not pins on this hw, and I
notice that I don't always get 3 devices, so I'm not sure if devices
are a dynamic thing we should be reprobing on some signal.

Dave.