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

[Wang, Xingchao]

+Rafael.

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Wednesday, July 24, 2013 7:02 PM
> To: Wang, Xingchao
> Cc: Paulo Zanoni; Daniel Vetter; daniel.vetter at ffwll.ch;
> alsa-devel at alsa-project.org; intel-gfx at lists.freedesktop.org; Girdwood, Liam
> R; Jin, Gordon; David Henningsson
> Subject: Re: [alsa-devel] [Intel-gfx] [PATCH 0/4 V7] Power-well API
> implementation for Haswell
> 
> 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?

Yes, seems it was changed by App through sysfs. I donot' know much about the user space power manager policy, could Rafael share some information?

> 
> > 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?

I will continue looking into this change.
> 
> > 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.

Yes, I agree. I'm debugging this issue on Ubuntu, not sure it happens on other distribution too.
If it's related to Ubuntu, maybe need check Ubuntu power policy. Does anyone know the Ubuntu power-policy on laptop?
i.e. when charger connected, will Ubuntu make decision to disable power-save feature for audio subsystem?

> 
> 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 for clarify this. I also think it's not a good solution to make changes inside audio dirver. :(
Donot worry, I will continue to investigate this.

Thanks
--xingchao

> 
> 
> 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)>]
> >