[alsa-devel] [PATCH v3 1/1] ALSA: hda - bug fix for invalid connection list of Haswell HDMI codec pins

Lin, Mengdong mengdong.lin at intel.com
Thu Jan 17 04:23:27 CET 2013

> -----Original Message-----
> From: David Henningsson [mailto:david.henningsson at canonical.com]
> Sent: Tuesday, January 15, 2013 6:51 PM

> When trying to get Haswell HDMI audio working, I discovered that this verb
> when executed can get pins to change state from D0 to D3.
> As the fixup is executed after hda_call_codec_resume this means that the
> pins will remain in D3. I'm not entirely sure of this, but I think we have no
> runtime power transitions if we are on AC power, so this could potentially be
> for a very long time.

Hi David,

Is the "power save" enabled for the codec, by setting a non-zero value to the 
"power_save" parameter under /sys/module/snd_hda_intel/parametesrs?

The verb 0x0f81/0x0781/ is a vendor verb to query/configure HDMI, but it will
not touch the pin's D-state.

I suspect the codec is suspended in D3 during the interval between commands
execution, since codec_exec_verb() will call snd_hda_power_down() after a 
command is done and so the codec will be suspended if 'power save' is enabled. 
And snd_hda_codec_read() just tries to resume the codec when executing a 
new command, the calling sequence is snd_hda_codec_read-> codec_exec_verb
-> snd_hda_power_up.

> > +	/* override 3 pins connection list */
> > +	snd_hda_override_conn_list(codec, 0x05, 3, list);
> > +	snd_hda_override_conn_list(codec, 0x06, 3, list);
> > +	snd_hda_override_conn_list(codec, 0x07, 3, list);
> So before the DP 1.2 verb is executed, the connections are just 5 -> 2, 6 -> 3,
> 7 -> 4, but afterwards, every pin node can connect to every cvt node, and
> connection select verbs must change as a result?

Yes. Without DP 1.2 there is a 1:1 mapping between pins and convertors. But HDMI 
cannot play sound. And even DP 1.2 is enabled, HDMI codec can still report invalid 
empty connect list during initialization. This is a HW issue for Haswell B0 processor.

Which version of Haswell processor is on your machine? Could you share the 
'cpu stepping' in BIOS under platform information menu. 

We'll verify this issue and side effect of the patch after we got a processor upgrade.

Sorry for the late reply.


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