[Intel-gfx] [PATCH v5] drm/i915: pass ELD to HDMI/DP audio driver

[Purushothaman, Vijay A]

> -----Original Message-----
> From: intel-gfx-
> bounces+vijay.a.purushothaman=intel.com at lists.freedesktop.org
> [mailto:intel-gfx-
> bounces+vijay.a.purushothaman=intel.com at lists.freedesktop.org] On Behalf Of
> Wu Fengguang
> Sent: Monday, November 14, 2011 6:56 PM
> To: Takashi Iwai
> Cc: Wang, Zhenyu Z; intel-gfx at lists.freedesktop.org; Barnes, Jesse; Jeremy
> Bush; Christopher White; Bossart, Pierre-louis
> Subject: Re: [Intel-gfx] [PATCH v5] drm/i915: pass ELD to HDMI/DP audio
> driver
> 
> On Mon, Nov 14, 2011 at 05:45:12PM +0800, Takashi Iwai wrote:
> > At Sat, 12 Nov 2011 10:27:26 +0800,
> > Wu Fengguang wrote:
> > >
> > > (snip)
> > > > > > > > And I'm not sure whether HDMI audio is played
> > > > > > > > while DPMS is off.  I haven't tested it.
> > > > > > >
> > > > > > > It will go silence on DPMS. I noticed this while doing long
> term HDMI
> > > > > > > audio playback tests.  This should better be fixed in future on
> the
> > > > > > > graphics side.
> > > > > >
> > > > > > Hm, but I wonder what could be done alternatively.
> > > > > > Hopefully there is a register for video-only control...
> > > > >
> > > > > There may be some mode that can keep video off while still keep
> > > > > minimal signals to play HDMI sound?
> > > >
> > > > Let's hope :)

You can turn off only the plane (but don't turn off the pipe & port) to achieve this.

Not much of power saving compared to DPMS though.

> > >
> > > Looks very possible, here is the clue of hardware support:
> > >
> > >         TRANS_DP_CTL - Transcoder DisplayPort Control
> > >
> > >         bit 26: Transcoder DP Audio Only Mode
> >
> > Good to know!  But what about HDMI?
> 
> I'm not sure.. There are no corresponding TRANS_HDMI_CTL registers...
> 

Bit 26 of TRANS_DP_CTL does not work. Also there is no such bit for HDMI.

> Thanks,
> Fengguang
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Thanks,
Vijay