[alsa-devel] DP MST audio support

[Takashi Iwai]

At Thu, 14 May 2015 09:10:33 +1000,
Dave Airlie wrote:
> 
> 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?

Sorry, I've been on vacation for last two weeks.  Now still swimming
in the flood of backlogs...

> 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.

The intel_not_share_assigned_cvt() was needed for Haswell HDMI/DP as
there was static routing between the pin and the converter widgets
although the codec graph shows it's selectable.

Was the pin default config of pin 6 enabled by BIOS properly?

In anyway, Intel people should have a better clue about this; it's
been always a strange behavior that is tied with the graphics...


thanks,

Takashi