[alsa-devel] radeon multi-channel lpcm

[Takashi Iwai]

At Wed, 5 Sep 2012 18:19:23 +0200,
Pierre Ossman wrote:
> 
> Noone with any insight? I'm ready to do some leg work, but I couldn't
> find anything in either the HDA specification, or the AMD
> documentation. :/

Well, HD-audio HDMI codec driver just extracts the available channel
setup from the given ELD, and the ELD data is sent from the graphics
driver.  So, if anything missing in ELD, it's supposed to be in the
graphics driver side.  In other words, if ELD doesn't give 6 channels,
HD-audio codec won't follow that channel setup, too.


Takashi

> 
> On Fri, 31 Aug 2012 22:34:47 +0200
> Pierre Ossman <pierre-list at ossman.eu> wrote:
> 
> > Hi,
> > 
> > I figured I'd have a go at finishing up support for multi-channel lcpm
> > over HDMI on radeon cards. I read a post from the AMD guys stating that
> > the GPU portions were already in place, and it was the audio pieces
> > that were missing. Unfortunately I was unable to figure out exactly what
> > it is that remains to be done.
> > 
> > I poked around in patch_hdmi.c, and concluded that the generic code is
> > what's being used for modern radeon cards. The card exposes two widgets
> > (and output widget and a pin complex). But both widgets indicate
> > through their capability registers that they only support stereo.
> > 
> > I don't know enough about HDA to have any clue where to go from here.
> > Should the capability field be ignored for HDMI? Or does it need some
> > coaxing to allow more than stereo? The ELD stuff isn't properly updated
> > from the radeon driver, but the code seems to suggest it is just for
> > hints, and not critical.
> > 
> > Rgds
> 
> 
> -- 
>      -- Pierre Ossman
> 
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