[Bug 89419] [SKL][Audio][HD-A Display]: Can't detect Display audio codec if not connect HDMI and DP monitor when boot up

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89419

--- Comment #19 from Libin Yang <libin.yang at intel.com> ---
Hi Imre,

Thanks for reply. Please see my comments below.


> 
> What I meant is that the EM4/5 registers do not exist on SKL. Adding simply
> the AZX_DCAPS_I915_POWERWELL flag to AZX_DCAPS_INTEL_SKYLAKE would result in
> programming these registers also on SKL, which is incorrect, so that
> programming needs to be avoided.

OK, I see. This should be another issue. I will fix this issue later. 

> 
> > For the power well, yes, we need set the power well before HDMI codec
> > detection. And the audio driver does do it already.
> 
> It didn't do it, you need to set AZX_DCAPS_I915_POWERWELL for that.

I added the flag AZX_DCAPS_I915_POWERWELL and did the test yesterday. The test
result is the same. Sometimes, the codec will not be recognized.

> 
> > After power well on, we will do the HDMI codec detection. We won't power off
> > the power well before HDMI codec detection.
> > 
> > BTW: I have asked the BIOS team about this issue. They told me that we
> > should:
> > 1. update the BIOS to latest (we have already done)
> > 2. update the gfx driver to latest(windows). So I believe that BIOS may have
> > changed some interfaces with gfx for this issue. Maybe we missed the change?
> 
> I'm not aware of any other interaction between the gfx and sound driver
> besides what is done via the i915/audio component framework. For SKL in
> practice this means turning on and off power well 2. I still suspect that
> after turning power well 2 off then back on (this sequence actually happens
> based on the attached dmesg) some of the audio HW state gets reset and is
> not reinitialized properly. I would probably start enabling debugging in the
> sound driver and see where the detection fails.

For " power well 2", do you mean the functions in audio driver
"hda_i915_init()" and "hda_display_power()" will handle it? If so, audio driver
doesn't call hda_display_power(hda, false) will not turn the power well2 off,
right? Or gfx driver will turn off the power well that audio driver is not
realized?

> 
> (In reply to Libin Yang from comment #16)
> > Hi Imre,
> > 
> > I found SKL doesn't apply the powerwell flag. I will test by adding the flag
> > although it shouldn't add the flag here. Will update the test result later.
> 
> Not sure what you mean here. The sound driver needs to turn on/off its
> dependent power well (power well 2 in case of SKL), and it does this on
> platforms with the AZX_DCAPS_I915_POWERWELL flag set. So the flag needs to
> be set for SKL.

Yes. I added the flag and tested it internally, it didn't work. And you are
right, although it can't fix the audio codec detect issue. We really need this
flag as we are using the HDMI codec. I will check with Takashi whether adding
the flag is OK as you know this flag is mainly for HDA controller.

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