[RFC 00/13] acpi/x86: s2idle: implement Modern Standby transition states and expose to userspace

Fri Nov 22 23:55:16 UTC 2024

On Fri, 22 Nov 2024 at 20:26, Xaver Hugl <xaver.hugl at kde.org> wrote:
>
> Am Do., 21. Nov. 2024 um 18:22 Uhr schrieb Antheas Kapenekakis
> <lkml at antheas.dev>:
> >
> > The following series moves the _DSM 3,4,7,8 firmware notifications outside
> > the suspend sequence, and makes them part of a transition function, where
> > the system can transition freely between them when it is not suspended.
> > This transition function is exposed to userspace, which now gains the
> > ability to control the presentation of the device (e.g., pulse the suspend
> > light) without forcing the kernel to suspend. In addition, it adds support
> > for the _DSM 9 call Turn Display On, which was introduced in Windows 22H2
> > and aims to speed up device wake-up while remaining in the "Sleep" state.
> > If userspace is not standby aware, the kernel will bring the system into
> > the "Sleep" state before beginning the suspend sequence.
> >
> > This series requires a bit of background on how modern standby works in
> > Windows. Windows has a concept of "Modern Standby" [1], where it performs
> > an elaborate userspace and kernel suspend choreography while the device is
> > inactive in order to maintain fast wake-up times and connectivity while the
> > display of the device is off. This is done through 5 hardware states and
> > the OS takes the liberty of transitioning between them, by following a set
> > of rules (e.g., "Adaptive Hibernate").
> >
> > ```
> >                                  \/-> "Hibernate (S4)"
> > "Active" <-> "Screen Off" <-> "Sleep" <-> "DRIPS"
> >                   /\-  "Resume"  <-         <-
> > ```
> >
> > When the display is on and the user is interacting with the device, it is
> > in the "Active" state. The moment the display turns off, the device
> > transitions to the "Screen Off" state, where hardware and userspace are
> > fully active. Userspace will then decide when appropriate to freeze major
> > components (such as the DE) and transition into the "Sleep" state, where
> > the kernel is still active and connectivity is maintained. Finally, the
> > conventional "Suspend-to-idle" path can be used to bring the system into
> > the deepest runtime idle platform state (DRIPS) state, which is named
> > "s2idle" in the Linux kernel.
> >
> > After wake-up, the system re-transitions into the "Sleep" state, where
> > userspace can run housekeeping and/or hibernate if the wake-up was not user
> > initiated (e.g., timer). If user-initiated, userspace can hasten the
> > transition out of the "Sleep" state by transitioning into the state
> > "Resume" that certain devices use to boost the Power Limit (PLx) while
> > remaining in sleep (support for this new notification is rare). Then, it
> > transitions back into "Screen Off" and "Active" to prepare for the user.
> >
> > All transitions between these states feature unique firmware notifications
> > [3] that change the presentation of the device (e.g., pulse the suspend
> > light, turn off RGB). For more information, see the docs in [8]. Making
> > these transitions accessible from userspace moves them out of the suspend
> > sequence and has them happen while the kernel is fully active, mirroring
> > Windows.
> >
> > As a side effect, this patch series completely fixes the ROG Ally
> > controller issue [5], which expects for .5s to lapse before its
> > controller's USB hub goes into D3 and otherwise malfunctions. It also fixes
> > an issue present in (allegedly only) older firmwares where they check the
> > USB subsystem is not in D3 before allowing the controller to wake up while
> > in powersave mode (for avoiding spurious wake-ups). As such, this patch
> > series is also a universal fix for the ROG Ally controller.
> >
> > Moreover, this patch series allows turning off the controller and RGB of
> > most Windows handhelds (OneXPlayer, Lenovo Legion Go, GPD, and Asus ROG
> > Ally), opening the possibility of implementing suspend-then-hibernate and
> > other standby features, such as background downloads, without waking up the
> > RGB/controller of those devices. A Thinkpad T14 2021 was also tested, and
> > it pulses its suspend light during sleep.
> >
> > There is still the question of where LSP0 entry/exit (_DSM 5,6) should be
> > fired or whether they should be fired in the path to hibernation. However,
> > as they cause no issues currently, and they fire when software activity has
> > seized, they are fine where they are.
> >
> > It is important to note that the effects of these _DSMs persist during
> > reboots. I.e., if the Legion Go reboots while in the "Sleep" state, it will
> > boot into the "Sleep" state and have its controller disabled and suspend
> > light pulsing. The reboot persistence is undesirable, so the reboot path
> > will need to include a transition to active prior to reboot (not
> > included in this series). This is not the case after shutdown and
> > hibernation, where the device boots into the "Active" state.
> >
> > The issue of DPMS is still present. Currently, gamescope and KDE (at least)
> > do not fire DPMS before suspending. This causes an undesirable frozen
> > screen while the system is suspending and looks quite ugly in general. This
> > is especially true if the firmware notifications fire earlier. Therefore,
> > should the kernel fire DPMS before forcing the transition to sleep for
> > backwards compat.?
>
> FWIW in KDE we already planned to turn the screen off before suspend
> to deal better with spurious wakeups, and that'll be in the next
> version of Plasma. I think it's fine if you just leave this up to
> userspace, and maybe write to wayland-devel, so that other compositor
> developers are aware they should do the same.

This is really good to hear! I think that that is the proper solution,
along with instantly transitioning to screen off. This way the
keyboard backlight and the screen turn off instantly as the user
presses the power button. The fastest the kernel can do it is after
userspace freeze, which takes around .5s.

I still think we will have to do something in-kernel compat though, as
if we don't there is around 300ms between the device suspend light
starting to pulse and the drm driver turning off the display
currently. While it is a small visual regression, it is a regression
nonetheless and there are devices that depend on the USB subsystem
being up when the firmware notifications fire, so it cannot happen
after drm suspends.

We have not had any other reports whatsoever though and it is not as
if anyone has noticed this quirk.

@Mario while bisecting the hibernation issue, I also tested the Ally
with powersave on on a 6.10 stock kernel. While the controller does
wake up, setting RGB stops working after a few suspends

> > If yes, it will be quite the effort. Moreover, should
> > the kernel allow graphics drivers hook the transition function and block
> > transitions to "Screen Off" if there is an active CRTC? As that would be a
> > significant undertaking, there should be proof that there exists such a
> > device that has an issue firing the notifications with an active CRTC.
> >
> > A variant of this series has been tested by thousands of users by now,
> > where the notifications fire around .5s before the CRTC is disabled and no
> > ill-effects have found in regard to this quirk. AFAIK, it is a visual
> > quirk. Making DPMS fire before the backwards compat. transition is a good
> > idea in any case, as it will sync the 200ms between Display Off/Sleep Entry
> > firing and the graphics driver turning off the display, but it might not be
> > worth the effort.
> >
> > We are currently testing a DPMS patch for gamescope and it completely fixes
> > this visual quirk while allowing for e.g., hibernation without turning on
> > the screen. The DPMS gamescope patch + performing the transitions in
> > userspace in such a way where it blends the Ally's suspend delay halves the
> > user perceived delay to sleep and results in a very professional
> > presentation. This presentation extends to other devices as well, such as
> > the Legion Go.
> >
> > Link: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/prepare-hardware-for-modern-standby [1]
> > Link: https://learn.microsoft.com/en-us/windows-hardware/customize/power-settings/adaptive-hibernate [2]
> > Link: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/modern-standby-firmware-notifications [3]
> > Link: https://github.com/hhd-dev/hwinfo/tree/master/devices [4]
> > Link: https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/log/?h=superm1/dsm-screen-on-off [5]
> > Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2719 [6]
> > Link: https://dl.dell.com/manuals/all-products/esuprt_solutions_int/esuprt_solutions_int_solutions_resources/client-mobile-solution-resources_white-papers45_en-us.pdf [7]
> > File: Documentation/admin-guide/pm/standby-states.rst [8]
> >
> > Changes from previous series (`acpi/x86: s2idle: move Display off/on calls
> >   outside suspend (fixes ROG Ally suspend)`):
> >   - Separate Display On/Off rename into its own commit (suggested by Hans)
> >   - Move delay quirks into s2idle.c (suggested by Hans)
> >   - Add documentation on Documentation/admin-guide/pm/standby-states.rst
> >   - Callbacks are now static and a transition function is used
> >   - Fixed all checkpatch warnings
> >   - The rest of the series is completely re-written
> >
> > Antheas Kapenekakis (13):
> >   Documentation: PM: Add documentation for S0ix Standby States
> >   acpi/x86: s2idle: add support for Display Off and Display On callbacks
> >   acpi/x86: s2idle: add support for Sleep Entry and Sleep Exit callbacks
> >   acpi/x86: s2idle: add support for Turn On Display callback
> >   acpi/x86: s2idle: add modern standby transition function
> >   acpi/x86: s2idle: rename Screen On/Off to Display On/Off
> >   acpi/x86: s2idle: call Display On/Off as part of callbacks
> >   acpi/x86: s2idle: rename MS Exit/Entry to Sleep Exit/Entry
> >   acpi/x86: s2idle: call Sleep Entry/Exit as part of callbacks
> >   acpi/x86: s2idle: add Turn On Display and call as part of callback
> >   acpi/x86: s2idle: add quirk table for modern standby delays
> >   platform/x86: asus-wmi: remove Ally (1st gen) and Ally X suspend quirk
> >   PM: standby: Add sysfs attribute for modern standby transitions
> >
> >  Documentation/ABI/testing/sysfs-power         |  34 +++
> >  .../admin-guide/pm/standby-states.rst         | 133 ++++++++++
> >  Documentation/admin-guide/pm/system-wide.rst  |   1 +
> >  drivers/acpi/x86/s2idle.c                     | 249 ++++++++++++++----
> >  drivers/platform/x86/asus-wmi.c               |  54 ----
> >  include/linux/suspend.h                       |  16 ++
> >  kernel/power/main.c                           |  75 ++++++
> >  kernel/power/power.h                          |   1 +
> >  kernel/power/suspend.c                        | 154 +++++++++++
> >  9 files changed, 616 insertions(+), 101 deletions(-)
> >  create mode 100644 Documentation/admin-guide/pm/standby-states.rst
> >
> > --
> > 2.47.0
> >
> >