Re: force DVI mode without audio

[Wu Fengguang <fengguang.wu@intel.com>]

On Sat, Dec 31, 2011 at 01:20:11PM +0100, Andrea Arcangeli wrote:
> On Sat, Dec 31, 2011 at 09:28:37AM +0800, Wu Fengguang wrote:
> > Hi Andrea,
> > 
> > On Fri, Dec 30, 2011 at 08:07:27PM +0100, Andrea Arcangeli wrote:
> > > Hi,
> > > 
> > > after upgrading my HTPC to HD3000 graphics (2700K), I didn't find
> > > anymore a way to disable the hdmi audio from the DVI2HDMI cable (I
> > > connect DVI output of the motherboard to the HDMI input of the LCDTV
> > > in HD). So I added it to the driver as it looks a missing tweak that I
> > > need.
> > > 
> > > (I also have proper audio setup connected to the second output of the
> > > soundcard, but unless I watch a movie or listen music I keep it off so
> > > I like the LCDTV speaker to work too, and if I turn on the proper
> > > sound then I mute the TV)
> > > 
> > > With the readon I was using radeon.audio=0 at boot to achieve the
> > > exact same thing. Without this, the LCDTV won't play the audio coming
> > > from the line in analog cable as it's fooled into thinking the audio
> > > comes through the hdmi cable when it cannot.
> > > 
> > > It's all working perfectly now.
> > 
> > Have you tried the "audio" property which can be listed with
> > 
> >         xrandr --prop
> 
> I wasn't aware about this one, thanks for the tip.
> 
> I tried:
> 
>         xrandr --output HDMI1 --set "audio" off
> 
> that made the sound working for half a second, then it stops working.
> 
> If I run:
> 
>         xrandr --output HDMI1 --set "audio" on
>         xrandr --output HDMI1 --set "audio" off
> 
> at every invocation (including "on") I can hear sound for half a
> second and then it stops no matter if it's left on or off.

That's an interesting bug. What's the kernel version you are running?
The dmesg may tell something (especially if boot with "drm.debug=6").

> So I applied my patch again for now. If you fix the above I guess
> adding a little script to my KDE autostart directory would work fine.

OK.

> Also note, CTRL+ALT+F1 going back to console doesn't help either. I
> didn't try to play audio before starting X though, not sure what
> happens if I never run X and I try to play audio.

Yeah, that could be a problem. I see that

/sys/class/drm/card0/card0-HDMI-A-1/

exports several drm connector properties, however the (currently still
i915 specific) "audio" property is not there. It should be good to
make it a general one and export it in drivers/gpu/drm/drm_sysfs.c.

> BTW, initially I tried to set only has_audio to false, but that wasn't
> enough I had to set hdmi to off too and force it to DVI mode to make
> audio work with my TVLCD (LG brand).

You mean the "has_hdmi_sink = false"? Well does that mean we need to
one more property for it? The property _interface_ is per port, which
can support 2+ HDMI/DP jacks well.

Thanks,
Fengguang