[alsa-devel] HD-audio runtime PM

Wang Xingchao wangxingchao2011 at gmail.com
Tue Nov 26 02:05:20 CET 2013

Hi Takashi,

2013/11/22 Takashi Iwai <tiwai at suse.de>:
> Hi,
> after my previous fix, the runtime PM seems working stably finally.
> However, there seem still some glitches:
> 1. The wakeup via jack or HDMI/DP detection doesn't seem to work on my
>   test machines.  WAKEEN is set properly.  And its value can be read
>   correctly at the point of runtime resume, too.
> 2. We don't change the device to D3 in runtime suspend.  So I guess we
>   save little power as of now.
>   Actually, setting to D3 and resuming to D0 works fine, as far as I
>   tested -- except for HDMI/DP ELD read out on Haswell.  Although ELD
>   read doesn't give any errors, the received bytes are corrupted.  In
>   my case, the read starts from offset 0x1c.
>   The HDMI can be still played even at that state, but then it falls
>   back to the stereo 2ch mode, of course.
> The tests were performed on both Haswell (DP and LynxPoint-LP) and
> IvyBridge (PantherPoint) machines.
> The first problem has been present, and it's also the behavior of some
> old chips where the codec can't go to sleep with unsol wakeup.  So, in
> this regard, it's no regression, per se.  But certainly it's no good
> thing.
> I thought Mengdong once made WAKEEN working.  Mengdong, do you
> remember what was the condition?  Could you check whether the latest
> kernel (at best sound git tree for-linus branch) still works?
> About the second point: we should do D3 if we do care power, and
> that's the very right reason for runtime PM.  But the ELD issue is a
> bad bug, and it makes me wonder whether it's a graphics driver side
> issue or a codec side.  As a quick workaround, we can implement D3 on
> controllers but for Haswell HDMI/DP.

I didnot follow alsa-devel threads often now, is that ELD issue an
regression from my previous commit?
I test WAKEEN feature on Haswell machines before, it could really
wakeup system from D3.
The controller must be in RESET mode after enter runtime-suspend,
otherwise it will not be waken up
even if codec send out wake-up event. And STATESTS will be cleared
after controller brought out of RESET mode.

> In anyway, this is no urgent issue, clearly targeted for 3.14.
> The whole patch series are found in my sound-unstable git tree
> test/hda branch.
>   git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-unstable.git
> thanks,
> Takashi
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