Nouveau - May 2017 - [Intel-gfx] [PATCH v2 5/5] ACPI: button: Obselete acpi_lid_open() invocations

Hi Lv,

On Mon, May 15, 2017 at 5:55 AM, Zheng, Lv <lv.zheng at intel.com>
wrote:
> Hi, Benjamin
>
>> From: linux-acpi-owner at vger.kernel.org [mailto:linux-acpi-owner at
vger.kernel.org] On Behalf Of Benjamin
>> Tissoires
>> Subject: Re: [PATCH v2 5/5] ACPI: button: Obselete acpi_lid_open()
invocations
>>
>> Hi Lv,
>>
>> I am trying to reduce the number of parallel discussion we have on the
>> same subject, but there is something here I can't let you have.
>
> OK. So let's stop talking in PATCH 4-5.
> They are actually cleanups from my point of view.
>
> In fact, I don't see any big conflicts between us.
>
> My point of view is:
> There is a gap between (BIOS ensured/Windows expected) acpi control method
lid device behavior and Linux user space expected acpi control method lid device
behavior.
> Button driver default behavior should be: button.lid_init_state=ignore
> If user space programs have special needs, they can fix problems on their
own, via the following mean:
>  echo -n "open" >
/sys/modules/button/parameters/lid_init_state
>  echo -n "close" >
/sys/modules/button/parameters/lid_init_state
> Keeping open/close modes is because I don't think there is any bug in
button driver.
> So I need to prepare quirk modes from button driver's point of view and
use them as a response to related bug reports reported in acpi community.
> Your point of view is:
> There is a gap between (BIOS ensured/Windows expected) acpi control method
lid device behavior and Linux user space expected acpi control method lid device
behavior.
> Button driver default behavior should be (not 100% sure if this is your
opinion): button.lid_init_state=method
> If user space programs have special needs, they can fix them on their own,
via the following mean:
>  libinput:name:*Lid Switch*:dmi:*svnMicrosoftCorporation:pnSurface3:*
>   LIBINPUT_ATTR_LID_SWITCH_RELIABILITY=write_open
> From this point of view, we actually don't need open/close modes.
>
> It seems we just need to determine the following first:
> 1. Who should be responsible for solving bugs triggered by the conflict
between bios and linux user space expectations:
>    button driver? libinput? Some other user space programs? Users?
> 2. What should be the default button driver behavior?
>    button.lid_init_state=ignore? button.lid_init_state=method?
> 3. If non button driver quirks are working, button driver quirk modes are
useless.
>    The question is: Should button.lid_init_state=open/close be kept?
> 4. From button driver's point of view, button.lid_init_state=ignore
seems to be always correct, so we won't abandon it.
>    If we can use libinput to manage platform quirks, then
button.lid_init_state=method also looks useless.
>    The question is: Should button.lid_init_state=method be kept?
I'll answer everything in the other thread, where there are slightly
more other points raised:
https://lkml.org/lkml/2017/5/15/10
>
> I should also let you know my preference:
> 1. using button.lid_init_state=ignore and button.lid_init_state=method as
default behavior is ok for me if answer to 1 is not button driver, otherwise
using button.lid_init_state=method is not ok for me
> 2. deletion of button.lid_init_state=open/close is ok for me if answer to 1
is not button driver, otherwise deletion of button.lid_init_state=open/close is
not ok for me
> 3. deletion of button.lid_init_state=method is always ok for me
>
> See the base line from my side is very clear:
> If acpi community need to handle such bug reports,
button.lid_init_state=method cannot be the default behavior.
> We are just using a different default behavior than "method" to
drive things to reach the final root caused solution.
>
> Could you let me know your preference so that we can figure out an
agreement between us.
> Though I don't know if end users will buy it (they may keep on filing
regression reports in ACPI community).
>
> Can this make the discussion simpler?
I really hope so :)

Cheers,
Benjamin
>
> So before determining whether we should keep
button.lid_init_state=open/close or not.
> We obviously should stop talking here.
> You can copy above questions to PATCH 1-2 discussion and reply in order to
stop this.
> We can revisit PATCH 4-5 when the basic questions are answered. :)
>
>>
>> On Fri, May 12, 2017 at 8:08 AM, Zheng, Lv <lv.zheng at
intel.com> wrote:
>> > Hi,
>> >
>> > If my previous reply is not persuasive enough.
>> > Let me do that in a different way.
>> >
>> >> From: linux-acpi-owner at vger.kernel.org
[mailto:linux-acpi-owner at vger.kernel.org] On Behalf Of Zheng,
>> >> Lv
>> >> Subject: RE: [PATCH v2 5/5] ACPI: button: Obselete
acpi_lid_open() invocations
>> >>
>> >> Hi,
>> >>
>> >> > From: Benjamin Tissoires [mailto:benjamin.tissoires at
gmail.com]
>> >> > Subject: Re: [PATCH v2 5/5] ACPI: button: Obselete
acpi_lid_open() invocations
>> >> >
>> >> > On Tue, May 9, 2017 at 9:02 AM, Lv Zheng <lv.zheng at
intel.com> wrote:
>> >> > > Since notification side has been changed to always
notify kernel listeners
>> >> > > using _LID returning value. Now listeners
needn't invoke acpi_lid_open(),
>> >> > > it should use a spec suggested control method lid
device usage model:
>> >> > > register lid notification and use the notified value
instead, which is the
>> >> > > only way to ensure the value is correct for
"button.lid_init_state=ignore"
>> >> > > mode or other modes with
"button.lid_fake_events=N" specified.
>> >> > >
>> >> > > This patch fixes i915 driver to drop acpi_lid_open()
user. It's not
>> >> > > possible to change nouveau_connector.c user using a
simple way now. So this
>> >> > > patch only marks acpi_lid_open() as deprecated to
accelerate this process
>> >> > > by indicating this change to the nouveau developers.
>> >> >
>> >> > If  the only 2 users of acpi_lid_open() are intel and
nouveau, and if
>> >> > they should rely on the value stored in the input node,
not the one
>> >> > exported by the _LID method (which can be wrong on some
platforms),
>> >> > how about simply changing the implementation of
acpi_lid_open() to
>> >> > fetch the value from the input node directly?
>> >
>> > If acpi_lid_open() returns stored value in input node,
>> > then it actually returns the value we notified to the input layer.
>> > While i915 and nouveau explicitly do not trust that value and
invoke acpi_lid_open().
>> >
>> > For button.lid_init_state=method, PATCH 4/5 is useless as the
values are same.
>> >
>> > However in my reply of PATCH 2.
>> > I explained the difference of method/close, for the same reason,
we can also sense the difference of
>> method/open.
>> > The difference then can explain the usefulness of open/close
modes.
>> >
>> > Given open/close modes are all useful:
>> > button.lid_init_state=open
>> > 1. button driver sends open to input layer after boot/resume
>> > 2. i915/nouveau uses _LID return value after boot/resume
>> > If _LID return value after boot/resume is "close", they
are different.
>> >
>> > button.lid_init_state=close
>> > 1. button driver sends close to input layer after boot/resume
>> > 2. i915/nouveau uses _LID return value after boot/resume
>> > If _LID return value after boot/resume is "open", they
are different.
>> >
>> > The only way to be consistent to old i915/nouveau behavior is:
>> > button.lid_init_state=open/close
>>
>> But these two modes are wrong in the absolute case:
>> - a laptop has no reasons for not being powered up with the lid
>> physically closed (wake on lan?) -> so open is an approximation
>> already made on good assumption that there is not a high chance of the
>> users powering/resuming the laptop with the lid closed
>> - in the "close" case, this setting works for docked laptops,
but if
>> the laptop can be docked, it can also be undocked. And if you boot
>> with button.lid_init_state=close, undock your laptop, go into suspend,
>> resume -> the lid state is now "closed" while it should be
opened.
>>
>> So no, these are just workarounds. i915/nouveau expect the acpi/button
>> state to be reliable, or they should ignore it. But you can't fake
>> events when you are not absolutely sure of what is happening.
>>
>> > 1. button driver sends open/close to input layer after boot/resume
>> > 2. button driver sends _LID return value to i915 after boot/resume
(PATCH 4)
>> > So that i915 can just use the notified value in this patch (PATCH
5).
>> > For nouveau, no change has been made for now, and as a
concequence, acpi_lid_open() is still kept
>> but marked as deprecated.
>> >
>> >>
>> >> See my reply of PATCH 4.
>> >> It seems they trust _LID return value more than what we send
to them.
>> >>
>> >> We can actually send faked "open/close" to them when
button.lid_init_state=open/close is specified.
>> >>
>> >> So these 2 patches [PATCH 4-5/5] are used to do a small
cleanup for lid event notifier APIs.
>> >> I think they are not strictly related to the lid issues we are
talking about.
>> >
>> > See Documentation/acpi/acpi-lid.txt:
>> > The _LID control method is described to return the
"current" lid state.
>> > However the word of "current" has ambiguity, some buggy
AML tables return
>> > the lid state upon the last lid notification instead of returning
the lid
>> > state upon the last _LID evaluation.
>> >
>> > In order to have acpi lid event notifier API compliant to the
above mentioned both "buggy" and
>> "nonbuggy" implementation.
>> > The ensured lid event model interface should be:
>> > 1. Lid event notifier listeners invokes
acpi_lid_notifier_register().
>> > 2. And in the callback, uses _LID return value.
>> > This is also the only possible way to combine "receiving lid
notify" and "evaluate _LID" into 1
>> single atomic operation.
>> >
>> > So I trend to remove acpi_lid_open() and enforce the new API.
>> >
>> > As a conclusion, PATCH 4-5
>> > 1. makes a hidden logic explicit - the lid event listeners always
use _LID return value. Less hidden
>> logics should leave less chances of bugs.
>> > 2. is an implementation for our documented ACPI lid event model.
>> > And the implementation is done in a regression safe way.
>>
>> I understand all of that. But my point is still that on some
>> platforms, the lid acpi state is not reliable, and the code in
>> i915/nouveau is not made for those platforms. So the ideal solution is
>> to know which platforms are problematic and take the right decisions
>> having everything at hands. Just "fixing" the internal API
won't help
>> teaching these drivers to not make the assumption that the _LID acpi
>> call is always correct.
>>
>> So yes, nouveau/i915 might need to be fixed, but IMO, fixing
>> acpi/button to report correct (true, accurate, actual, or physical if
>> you prefer) is the best, future proof way (minus platform quirks).
>
> This leads to endless discussion.
> Let's make agreement on above questions first.
>
> Cheers,
> Lv
>
>>
>> Cheers,
>> Benjamin
>>
>> >
>> > Thanks,
>> > Lv
>> >
>> >>
>> >> Cheers,
>> >> Lv
>> >>
>> >> >
>> >> > Cheers,
>> >> > Benjamin
>> >> >
>> >> > >
>> >> > > Cc: <intel-gfx at lists.freedesktop.org>
>> >> > > Cc: <nouveau at lists.freedesktop.org>
>> >> > > Signed-off-by: Lv Zheng <lv.zheng at
intel.com>
>> >> > > ---
>> >> > >  drivers/acpi/button.c             | 7 ++++++-
>> >> > >  drivers/gpu/drm/i915/intel_lvds.c | 2 +-
>> >> > >  2 files changed, 7 insertions(+), 2 deletions(-)
>> >> > >
>> >> > > diff --git a/drivers/acpi/button.c
b/drivers/acpi/button.c
>> >> > > index 7ff3a75..50d7898 100644
>> >> > > --- a/drivers/acpi/button.c
>> >> > > +++ b/drivers/acpi/button.c
>> >> > > @@ -348,7 +348,12 @@ int
acpi_lid_notifier_unregister(struct notifier_block *nb)
>> >> > >  }
>> >> > >  EXPORT_SYMBOL(acpi_lid_notifier_unregister);
>> >> > >
>> >> > > -int acpi_lid_open(void)
>> >> > > +/*
>> >> > > + * The intentional usage model is to register a lid
notifier and use the
>> >> > > + * notified value instead. Directly evaluating _LID
without seeing a
>> >> > > + * Notify(lid, 0x80) is not reliable.
>> >> > > + */
>> >> > > +int __deprecated acpi_lid_open(void)
>> >> > >  {
>> >> > >         if (!lid_device)
>> >> > >                 return -ENODEV;
>> >> > > diff --git a/drivers/gpu/drm/i915/intel_lvds.c
b/drivers/gpu/drm/i915/intel_lvds.c
>> >> > > index 9ca4dc4..8ca9080 100644
>> >> > > --- a/drivers/gpu/drm/i915/intel_lvds.c
>> >> > > +++ b/drivers/gpu/drm/i915/intel_lvds.c
>> >> > > @@ -548,7 +548,7 @@ static int
intel_lid_notify(struct notifier_block *nb, unsigned long val,
>> >> > >         /* Don't force modeset on machines where
it causes a GPU lockup */
>> >> > >         if
(dmi_check_system(intel_no_modeset_on_lid))
>> >> > >                 goto exit;
>> >> > > -       if (!acpi_lid_open()) {
>> >> > > +       if (!val) {
>> >> > >                 /* do modeset on next lid open event
*/
>> >> > >                 dev_priv->modeset_restore =
MODESET_ON_LID_OPEN;
>> >> > >                 goto exit;
>> >> > > --
>> >> > > 2.7.4
>> >> > >
>> >> > > --
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On Mon, 15 May 2017, Benjamin Tissoires <benjamin.tissoires at gmail.com>
wrote:
> I'll answer everything in the other thread, where there are slightly
> more other points raised: https://lkml.org/lkml/2017/5/15/10
If you are discussing changes impacting i915, please keep intel-gfx list
in the loop.

Thanks,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center

On Mon, May 15, 2017 at 10:42 AM, Jani Nikula
<jani.nikula at linux.intel.com> wrote:
> On Mon, 15 May 2017, Benjamin Tissoires <benjamin.tissoires at
gmail.com> wrote:
>> I'll answer everything in the other thread, where there are
slightly
>> more other points raised: https://lkml.org/lkml/2017/5/15/10
>
> If you are discussing changes impacting i915, please keep intel-gfx list
> in the loop.
>
I can add intel-gfx to the other thread if you want, but this will IMO
just add more noise to your list.
The question is whether or not the kernel should provide a fake state
for the _LID acpi call, and until we reach an agreement on how to
handle things, there is no point changing the currently working code
in i915.

It is true that there is an issue in i915 regarding the fact that
intel_lid_notify() doesn't use the provided value but calls
acpi_lid_open(), but this is something that can be solved in
https://bugs.freedesktop.org/show_bug.cgi?id=100923, when the
situation clarifies.

Cheers,
Benjamin