[Intel-gfx] [PATCH 15/19] drm/i915: HSW cdclk support

[Mika Kahola]

I did some testing on audio part with HDMI-HDMI and DP-HDMI cables
connected to my Haswell box. Before applying the patch I tested as a
reference with the latest -nightly (04-08-2015), 4.0-rc7. Unfortunately,
I failed to get any audio over HDMI cable. For a reference I tested with
the very same setup the vanillla kernel from Linus tree 4.0-rc7 and with
that kernel the audio worked ok. Then I did some GIT bisecting and it
turned out that the first commit that I failed to get audio working was
aa2fee4286e43b4784982b17669b02cc99c1ae55.

To test this patch audio functionality I checkout the -nightly version
that works for me and apply the patch and test it. I'll come back with
the results later on. 

I had the module option i915.disable_power_well=0

The test routine that I used for audio testing was
speaker-test -c 2 -r 48000 -f S16_LE -t pink --device=plughw:0,3

On Tue, 2015-04-07 at 15:52 +0200, Daniel Vetter wrote:
> On Tue, Apr 07, 2015 at 12:29:25PM +0300, Mika Kahola wrote:
> > Definitely a good idea to check the audio part as well if there is
> > a doubt that by changing CD clock the audio would fail. I can check
> > this and I'll get back once I have the results.
> 
> We force a full modeset, which should result in an interrupt on the audio
> side, which should result in the audio driver re-reading the current
> cdclk. If that's no the case it's buggy already.
> -Daniel

-- 
Mika Kahola, Intel OTC