[alsa-devel] [PATCH] ALSA: hda - using POS_FIX_LPIB on Broadwell HDMI Audio

[Takashi Iwai]

At Fri, 9 May 2014 10:08:19 +0000,
Lin, Mengdong wrote:
> 
> Hi,
> 
> We found the Broadwell HDMI audio regression is introduced by this patch:
> 
> commit dcb32ecd9a533f47ab652c5c5680bc50a7a822cd
> Author: Anssi Hannula <anssi.hannula at iki.fi>
> Date: Tue Apr 8 12:36:42 2014 +0300
> ALSA: hda - Do not assign streams in reverse order
> 
> We'll further check the root cause.
> Since this patch seems only affect the stream ID. Actually Intel GPU tool only find the stream ID is changed by this patch.
> 
> In addition, Haswell HDMI audio is not affected and works well. It seems there is HW behavior difference between HSW and BDW.

Thanks for spotting out!

This sounds like a weird hardware bug of BDW.  If any, we'd need to
introduce a flag indicating flipping this  lookup behavior depending
on the chip.


Takashi

> 
> Thanks
> Mengdong
> 
> > -----Original Message-----
> > From: David Henningsson [mailto:david.henningsson at canonical.com]
> > Sent: Friday, May 09, 2014 12:06 AM
> > To: Yang, Libin; Takashi Iwai
> > Cc: Lin, Mengdong; alsa-devel at alsa-project.org; Pierre-Louis Bossart
> > Subject: Re: [alsa-devel] [PATCH] ALSA: hda - using POS_FIX_LPIB on Broadwell
> > HDMI Audio
> > 
> > 
> > 
> > On 2014-05-08 09:58, Yang, Libin wrote:
> > > Hi Takashi,
> > >
> > > I tested the non-snoop mode. It's worse than snoop mode. Only noise can be
> > heard if using non-snoop mode.
> > >
> > > I add the print in the function azx_position_ok(). The below is the dmesg:
> > > [  119.509631] <0>posbuf: 26368, lpib: 16320, wallclk: 2330325 [
> > > 119.509674] snd_hda_intel 0000:00:03.0: IRQ timing workaround is
> > activated for card #0. Suggest a bigger bdl_pos_adj.
> > > [  119.509683] <0>posbuf: 26368, lpib: 16332, wallclk: 2331659 [
> > > 119.515467] <0>posbuf: 28224, lpib: 17444, wallclk: 2470504 [
> > > 119.523460] <0>posbuf: 30592, lpib: 18976, wallclk: 2662403 [
> > > 119.531431] <0>posbuf: 32128, lpib: 20508, wallclk: 2853751 [
> > > 119.594932] snd_hda_intel 0000:00:03.0: Unstable LPIB (20416 >=
> > > 16384); disabling LPIB delay counting
> > 
> > This looks quite bad - is it not a hardware bug if LPIB > CBL (CBL should be
> > 16384 in this case)?
> > 
> > 
> > --
> > David Henningsson, Canonical Ltd.
> > https://launchpad.net/~diwic
>