[Intel-gfx] [alsa-devel] [PATCH 0/4 V7] Power-well API implementation for Haswell

Wed Jul 24 13:02:15 CEST 2013

At Wed, 24 Jul 2013 10:31:22 +0000,
Wang, Xingchao wrote:
> 
> Hi Paulo,
> 
> Would you help verify attached patch to fix this issue for you?
> 
> The patch is based on Takashi's tree, the last commit is:
> commit 9b298cfe296c0f8e088b9ed9a670783a06005e6b
> I think it should be safe to merge into your tree. :)
> 
> I tested the patch on Harris Beach, it would let audio driver release power-well even with charger connected.
> 
> Please note maybe this is not the final solution for this issue as it breaks some rule from user's point of view.

Well, this patch is NACK from my side.
Sorry, but this is a wrong approach.

> Some background of this issue:
> This patch intended to fix power-well regression on Haswell.
> 
> On Harris Beach(Ultrabook with battery), there's only eDP panel connected by default, no HDMI/DP.
> And gfx driver needs enable some HW feature for eDP, power-well *must* be
> disabled in this scenario.
> - Witout charger connected, power-well feature is perfect
> - with charger connected, audio never release power-well.
> 
> Basically, power-well should be release if audio driver doesnot use it, that's
> why we enabled runtime power-save feature.
> 
> In second case above, with charger connected, the parameter under
> "/sys/devices/../power/control" become "on" always.

Why this is set to "on" *always*, even if the device can be actually
controlled via runtime PM?

> In audio driver side, power_save was set to "0", which disable power_down the
> codecs and controller, thus never release power->usage_count.

Why it is set to zero at all?

> And this blocks audio driver release power-well.
> 
> In the second case, if audio driver detect hdmi pins are free and no Apps
> opened device, it will eanble runtime power-save feature as an exception.
> 
> I test this patch on Harris beach with charger connected, the power-well could
> be released as expected.

The primary problem is that these flags are set.

You're trying to implement an "ignore stop-signs on the street if no
other cars are running around you" feature in a new auto-cruise
system.  It would work, but it's not what's accepted in general.
(And it makes things complicated and fragile.)

The real question is why there are two useless STOP signs there.

thanks,

Takashi

> Thanks
> --xingchao
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai at suse.de]
> > Sent: Thursday, July 18, 2013 5:35 PM
> > To: Wang, Xingchao
> > Cc: Daniel Vetter; Paulo Zanoni; daniel.vetter at ffwll.ch;
> > alsa-devel at alsa-project.org; intel-gfx at lists.freedesktop.org; Wang xingchao;
> > Girdwood, Liam R; Jin, Gordon; David Henningsson
> > Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well API
> > implementation for Haswell
> > 
> > At Thu, 18 Jul 2013 09:23:57 +0000,
> > Wang, Xingchao wrote:
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of
> > > > Daniel Vetter
> > > > Sent: Thursday, July 18, 2013 2:44 PM
> > > > To: Wang, Xingchao
> > > > Cc: Paulo Zanoni; daniel.vetter at ffwll.ch;
> > > > alsa-devel at alsa-project.org; Daniel Vetter;
> > > > intel-gfx at lists.freedesktop.org; Wang xingchao; Girdwood, Liam R;
> > > > Jin, Gordon; Takashi Iwai; David Henningsson
> > > > Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well API
> > > > implementation for Haswell
> > > >
> > > > On Thu, Jul 18, 2013 at 01:00:07AM +0000, Wang, Xingchao wrote:
> > > > > Hi Paulo/Daniel,
> > > > >
> > > > > Do you agree to export an API in gfx side for eDP case?
> > > > > Basically the api will let audio drver know which pipe in use.
> > > > > i.e. in the eDP only caes, audio driver Will know gfx is not using
> > > > > HDMI/DP and would
> > > > like to let power-well off.
> > > > > As there's the conflict when user expect display audio driver
> > > > > always active but
> > > > gfx need audio driver off.
> > > > > Audio driver could make decision to release power-well if it knows
> > > > > the eDP
> > > > only case through the API.
> > > > >
> > > > > OTOH, I think audio driver could also export an API for gfx side,
> > > > > if gfx driver need audio driver release power-well but it's in
> > > > > usage, It will call
> > > > this API and audio drvier will release power-well accordingly.
> > > > >
> > > > > This change make HDMI/DP hotplug handling complicated in audio
> > > > > driver side,
> > > > if audio driver release power-well, it would enter suspend mode.
> > > > > Meanwhile the user may expect it's in active mode, this may cause
> > > > > some
> > > > confuse.
> > > >
> > > > Afaik (and I know very little about audio) the audio side already
> > > > knows which pipes have audio enabled, since we set the respective bit only
> > when it's needed.
> > > > And audio will receive the unsolicited even interrupt (or whatever
> > > > it's called) when this happens.
> > > >
> > > For haswell, Audio driver can get DDI port/Pin usage information according to
> > the unsolicited event, not Pipe info.
> > > However at this stage, seems only that is enough: if no pin has valid ELD,
> > audio driver can think about that no monitor connected with DDI ports.
> > > In this case, Audio driver could release power-well and enter suspend
> > > mode automatically, this avoid blocking eDP feature enabling. And once gfx
> > dirver Detect external monitor connected, it will also wake up audio driver.
> > >
> > > Takashi, do you think this solution acceptable?
> > 
> > It's the current situation, isn't it?  So the question is only whether this works
> > _as expected_.
> > 
> > Basically system/user needs to set up two parameters for the audio
> > power-saving.  If both are set well, but it still doesn't work, we need to debug.
> > 
> > Of course, we can improve things, for example, the default runtime PM setup.
> > (Note that this is about the default value, not the value force to set.)
> > 
> > 
> > Takashi
> > 
> > >
> > > Thanks
> > > --xingchao
> > >
> > > > So I think we already have the means (albeit with that quirky hw
> > > > interface, but it seems to have been good enough for a long time
> > > > already) to do that. Or do I miss something?
> > > > -Daniel
> > > >
> > > > >
> > > > > Thanks
> > > > > --xingchao
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Wang, Xingchao
> > > > > > Sent: Thursday, July 18, 2013 7:18 AM
> > > > > > To: 'Takashi Iwai'; David Henningsson; Paulo Zanoni
> > > > > > Cc: alsa-devel at alsa-project.org; Daniel Vetter;
> > > > > > daniel.vetter at ffwll.ch; intel-gfx at lists.freedesktop.org; Wang
> > > > > > xingchao; Girdwood, Liam R; Jin, Gordon
> > > > > > Subject: RE: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well
> > > > > > API implementation for Haswell
> > > > > >
> > > > > >
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Takashi Iwai [mailto:tiwai at suse.de]
> > > > > > > Sent: Wednesday, July 17, 2013 10:22 PM
> > > > > > > To: David Henningsson
> > > > > > > Cc: Paulo Zanoni; Wang, Xingchao; alsa-devel at alsa-project.org;
> > > > > > > Daniel Vetter; daniel.vetter at ffwll.ch;
> > > > > > > intel-gfx at lists.freedesktop.org; Wang xingchao; Girdwood, Liam
> > > > > > > R; Jin, Gordon
> > > > > > > Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7]
> > > > > > > Power-well API implementation for Haswell
> > > > > > >
> > > > > > > At Wed, 17 Jul 2013 16:05:43 +0200, David Henningsson wrote:
> > > > > > > >
> > > > > > > > On 07/17/2013 04:00 PM, Takashi Iwai wrote:
> > > > > > > > > At Wed, 17 Jul 2013 10:31:26 -0300, Paulo Zanoni wrote:
> > > > > > > > >>
> > > > > > > > >> 2013/7/17 Wang, Xingchao <xingchao.wang at intel.com>:
> > > > > > > > >>>
> > > > > > > > >>>
> > > > > > > > >>>> -----Original Message-----
> > > > > > > > >>>> From: Takashi Iwai [mailto:tiwai at suse.de]
> > > > > > > > >>>> Sent: Wednesday, July 17, 2013 4:18 PM
> > > > > > > > >>>> To: Wang, Xingchao
> > > > > > > > >>>> Cc: Paulo Zanoni; alsa-devel at alsa-project.org; Daniel
> > > > > > > > >>>> Vetter; daniel.vetter at ffwll.ch;
> > > > > > > > >>>> intel-gfx at lists.freedesktop.org; Wang xingchao;
> > > > > > > > >>>> Girdwood, Liam R; david.henningsson at canonical.com
> > > > > > > > >>>> Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7]
> > > > > > > > >>>> Power-well API implementation for Haswell
> > > > > > > > >>>>
> > > > > > > > >>>> At Wed, 17 Jul 2013 08:03:38 +0000, Wang, Xingchao wrote:
> > > > > > > > >>>>>
> > > > > > > > >>>>>
> > > > > > > > >>>>>
> > > > > > > > >>>>>> -----Original Message-----
> > > > > > > > >>>>>> From: Takashi Iwai [mailto:tiwai at suse.de]
> > > > > > > > >>>>>> Sent: Wednesday, July 17, 2013 3:34 PM
> > > > > > > > >>>>>> To: Wang, Xingchao
> > > > > > > > >>>>>> Cc: Paulo Zanoni; alsa-devel at alsa-project.org; Daniel
> > > > > > > > >>>>>> Vetter; daniel.vetter at ffwll.ch;
> > > > > > > > >>>>>> intel-gfx at lists.freedesktop.org; Wang xingchao;
> > > > > > > > >>>>>> Girdwood, Liam R; david.henningsson at canonical.com
> > > > > > > > >>>>>> Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7]
> > > > > > > > >>>>>> Power-well API implementation for Haswell
> > > > > > > > >>>>>>
> > > > > > > > >>>>>> At Wed, 17 Jul 2013 02:52:41 +0000, Wang, Xingchao wrote:
> > > > > > > > >>>>>>>
> > > > > > > > >>>>>>> Hi Takashi/Paulo,
> > > > > > > > >>>>>>>
> > > > > > > > >>>>>>>>>> would you change it to "auto" and test again.
> > > > > > > > >>>>>>>>>> Runtime power save should be enabled with "auto".
> > > > > > > > >>>>>>>>>
> > > > > > > > >>>>>>>>> Doesn't solve the problem. Should I open a bug
> > > > > > > > >>>>>>>>> report
> > > > > > > somewhere?
> > > > > > > > >>>>>>>>> Having the power well enabled prevents some power
> > > > > > > > >>>>>>>>> saving features from the graphics driver.
> > > > > > > > >>>>>>>>
> > > > > > > > >>>>>>>> Is the HD-audio power-saving itself working?  You
> > > > > > > > >>>>>>>> can check it via watching
> > > > > > > > >>>>>>>> /sys/class/hwC*/power_{on|off}_acct
> > > > files.
> > > > > > > > >>>>>>>>
> > > > > > > > >>>>>>>> power_save option has to be adjusted appropriately.
> > > > > > > > >>>>>>>> Note that many DEs change this value dynamically
> > > > > > > > >>>>>>>> per AC-cable plug/unplug depending on the
> > > > > > > > >>>>>>>> configuration, and often it's set to 0 (= no power
> > > > > > > > >>>>>>>> save) when AC-cable is
> > > > plugged.
> > > > > > > > >>>>>>>>
> > > > > > > > >>>>>>> [Wang, Xingchao] Paulo used a new Ultrabook board
> > > > > > > > >>>>>>> with charger connected,
> > > > > > > > >>>>>> and see the default parameter "auto=on".
> > > > > > > > >>>>>>> In such scenario, power-well is always occupied by
> > > > > > > > >>>>>>> Display audio controller. Moreover, in this board,
> > > > > > > > >>>>>>> if no external monitors connected, It's
> > > > > > > > >>>>>> using internal eDP and totally no audio support.
> > > > > > > > >>>>>> Power-well usage in such case also blocks some eDP
> > > > > > > > >>>>>> features as
> > > > Paulo told me.
> > > > > > > > >>>>>>>
> > > > > > > > >>>>>>> So I think it's not a good idea to break the rule of
> > > > > > > > >>>>>>> power policy when charger
> > > > > > > > >>>>>> connected but it's necessary to add support in this
> > > > > > > > >>>>>> particular
> > > > case.
> > > > > > > > >>>>>>> Takashi, do you think it's acceptable to let Display
> > > > > > > > >>>>>>> audio controller/codec
> > > > > > > > >>>>>> suspend in such case?
> > > > > > > > >>>>>>
> > > > > > > > >>>>>> Do you mean the driver enables the powersave forcibly?
> > > > > > > > >>>>>
> > > > > > > > >>>>> Yes. I mean call pm_runtime_allow() for the power-well
> > > > > > > > >>>>> HD-A
> > > > > > > controller.
> > > > > > > > >>>>>
> > > > > > > > >>>>>> Then, no, not in general.
> > > > > > > > >>>>>>
> > > > > > > > >>>>>> If the default parameter of autopm is the problem,
> > > > > > > > >>>>>> this should be changed, instead of forcing the policy in the
> > driver.
> > > > > > > > >>>>>>
> > > > > > > > >>>>>> OTOH, the audio codec's powersave policy is governed
> > > > > > > > >>>>>> by the power_save option and it's set up dynamically
> > > > > > > > >>>>>> by the desktop
> > > > > > system.
> > > > > > > > >>>>>> We shouldn't override it in the driver.
> > > > > > > > >>>>>>
> > > > > > > > >>>>>> If the power well *must* be off when only an eDP is used
> > (e.g.
> > > > > > > > >>>>>> otherwise the hardware doesn't work properly), then it's a
> > > > > > > > >>>>>> different story.  Is it the case?   And what exactly would
> > be
> > > > the
> > > > > > > > >>>>>> problem?
> > > > > > > > >>>>> In the eDP only case, no audio is needed for the HD-A
> > > > > > > > >>>>> controller, so it's
> > > > > > > > >>>> wasting power in current design.
> > > > > > > > >>>>> I think Paulo or Daniel could explain more details on the
> > impact.
> > > > > > > > >>>>
> > > > > > > > >>>> Consuming more power is the expected behavior.  What else?
> > > > > > > > >>>>
> > > > > > > > >>>>
> > > > > > > > >>>>>> If it's the case, controlling the power well based on
> > > > > > > > >>>>>> the runtime PM is likely a bad design, as it relies
> > > > > > > > >>>>>> on the parameter user
> > > > > > > sets.
> > > > > > > > >>>>>> (And remember that the power-saving of the audio can
> > > > > > > > >>>>>> be disabled completely via Kconfig, too.)
> > > > > > > > >>>>>  From audio controller's point of view, if it's asked
> > > > > > > > >>>>> be active, it needs power
> > > > > > > > >>>> and should request power-well from gfx side.
> > > > > > > > >>>>> In above case, audio controller should not be active
> > > > > > > > >>>>> but user set it be
> > > > > > > > >>>> "active".
> > > > > > > > >>>>
> > > > > > > > >>>> By setting the autopm "on", user expects that no
> > > > > > > > >>>> runtime PM
> > > > > > happens.
> > > > > > > > >>>> In other words, the audio controller must be kept
> > > > > > > > >>>> active as long as this parameter is set.  And this is
> > > > > > > > >>>> the parameter user controls, and not what the driver forcibly
> > sets.
> > > > > > > > >>>
> > > > > > > > >>> Okay, become clear now. :) So I think the conflict for
> > > > > > > > >>> Paulo becomes, in eDP caes, if audio is active
> > > > > > > and requested power-well, some eDP feature was under impact?
> > > > > > > > >>> Paulo, would you clarify this in more details?
> > > > > > > > >>
> > > > > > > > >> On our driver we try to disable the power well whenever
> > > > > > > > >> possible, as soon as possible. We don't change our
> > > > > > > > >> behavior based on power AC or other user-space modifiable
> > > > > > > > >> behavior (except the i915.disable_power_well Kernel
> > > > > > > > >> option). If the power well is not disabled we can't
> > > > > > > > >> enable some features, like PSR (panel self refresh, and
> > > > > > > > >> eDP feature) or PC8, which is another power-saving
> > > > > > > > >> feature. This will also make our QA procedures a lot more
> > > > > > > > >> complex since when we want to test specific features
> > > > > > > > >> (e.g., PSR, PC8) we'll have to disconnect the AC adapter
> > > > > > > > >> or run scripts. So the behavior/predictability of our
> > > > > > > > >> driver will be based on the Audio driver
> > > > > > > power management policies.
> > > > > > > > >
> > > > > > > > > So all missing feature are about the power saving?
> > > > > > > > >
> > > > > > > > >> I am not so experienced with general Linux Power
> > > > > > > > >> Management code, so maybe the way the Audio driver is
> > > > > > > > >> behaving is just the usual way, but I have to admit I was
> > > > > > > > >> expecting the audio driver would only require the power
> > > > > > > > >> well when it is actually needed, and release it as soon as possible.
> > > > > > > > >
> > > > > > > > > It would behave so, if all setups are for power-saving.
> > > > > > > > >
> > > > > > > > > But, in your case, the runtime PM control attribute shows
> > > > > > > > > "on"; it implies that the runtime PM is effectively
> > > > > > > > > disabled, thus disabling power well is also impossible
> > > > > > > > > (because it would require turning off the audio controller, too).
> > > > > > > >
> > > > > > > > So, if the machine only has an eDP (which has no audio
> > > > > > > > function in itself, right?) and never HDMI, DP output
> > > > > > > > because there are no such physical ports, the audio controller has no
> > function.
> > > > > > > > Maybe we can, before doing anything else, ask the video
> > > > > > > > driver first if this is the case, and if so, never create
> > > > > > > > the sound card at all, and just leave things the way the video driver
> > wants?
> > > > > > >
> > > > > > > Well, doesn't BIOS mark HDMI/DP audio pins as unused?  Then
> > > > > > > the audio driver won't create any instances.  Of course, we
> > > > > > > can optimize such a case, indeed.
> > > > > >
> > > > > > As I know, the eDP only case doesnot mean no HDMI/DP support.
> > > > > > User would plug in HDMI/DP monitor at any time.
> > > > > > So diable audio controller totoally is not a good idea. :(.
> > > > > > Paulo, is that correct for you case?
> > > > > >
> > > > > > --xingchao
> > > > > > >
> > > > > > >
> > > > > > > Takashi
> > > >
> > > > --
> > > > Daniel Vetter
> > > > Software Engineer, Intel Corporation
> > > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> > >
> [2 0001-ALSA-hda-Change-power-save-policy-for-power-well-reg.patch <application/octet-stream (base64)>]
> 