Re: [RFC v1 0/8] acpi/x86: s2idle: Introduce and implement runtime standby ABI for ACPI s0ix platforms

[Antheas Kapenekakis]

On Wed, 22 Apr 2026 at 10:51, Antheas Kapenekakis <lkml@xxxxxxxxxxx> wrote:
>
> On Wed, 22 Apr 2026 at 02:56, Dmitry Osipenko
> <dmitry.osipenko@xxxxxxxxxxxxx> wrote:
> >
> > Hi, Antheas
> >
> > On 3/17/26 14:04, Dmitry Osipenko wrote:
> > > On 3/16/26 22:36, Antheas Kapenekakis wrote:
> > >> On Mon, 16 Mar 2026 at 20:33, Antheas Kapenekakis <lkml@xxxxxxxxxxx> wrote:
> > >>>
> > >>> On Mon, 16 Mar 2026 at 20:03, Dmitry Osipenko
> > >>> <dmitry.osipenko@xxxxxxxxxxxxx> wrote:
> > >>>>
> > >>>> Hi Antheas,
> > >>>>
> > >>>> On 1/15/26 10:49, Antheas Kapenekakis wrote:
> > >>>>> On Thu, 15 Jan 2026 at 01:07, Dmitry Osipenko
> > >>>>> <dmitry.osipenko@xxxxxxxxxxxxx> wrote:
> > >>>>>>
> > >>>>>> On 1/13/26 13:11, Antheas Kapenekakis wrote:
> > >>>>>>> <snip>
> > >>>>>
> > >>>>> Hi Dmitry,
> > >>>>> let me go inline.
> > >>>>>
> > >>>>>> The primary goal is to support screen-off DSM for a power-efficient
> > >>>>>> background games downloading [1] and further resume-to-dark on Steam
> > >>>>>> Deck and other handhelds. There is no strict timeline, usual "sooner the
> > >>>>>> better". Downstreams will use customized WIP solution till upstream will
> > >>>>>> get necessary generic interfaces.
> > >>>>>>
> > >>>>>> [1] https://store.steampowered.com/news/app/1675200/view/771930569635267984
> > >>>>>
> > >>>>> Ok, this makes things clearer. I had done some testing to see the
> > >>>>> viability of such approach.
> > >>>>>
> > >>>>> One big problem [1] had was that the compression algorithm that Steam
> > >>>>> used was very CPU intensive. However, it was announced that that
> > >>>>> changed, which makes low power downloads more viable.
> > >>>>>
> > >>>>> However, even so, I do not think the sleep DSM is designed for
> > >>>>> prolonged background use and certain devices might overheat.
> > >>>>> Specifically, I think the Go S disables its fan while in that DSM.
> > >>>>> Looking back to what Windows does, it only uses the Sleep state to do
> > >>>>> periodic polling, and if there are updates it transitions to display
> > >>>>> off.
> > >>>>>
> > >>>>> This is a fair approach for [1]. For example, device wakes up every
> > >>>>> two hours while connected to a charger, stays on sleep state, checks
> > >>>>> for updates, and if there are any and conditions are met, transitions
> > >>>>> to display off and starts downloading.
> > >>>>>
> > >>>>> However, this means you do not get a smaller tdp limit. Given you
> > >>>>> control the unfrozen userspace in that state though, such a limit does
> > >>>>> not help either. The device will use what it needs to for downloads.
> > >>>>> This makes the SD 5W low power mode puzzling, as it means downloads
> > >>>>> will potentially take longer and I would be punished as a user for
> > >>>>> using that mode. Instead, Steam should be optimized to use less than
> > >>>>> 5W or perhaps 10W when downloading from gigabit in some way.
> > >>>>>
> > >>>>> Two more considerations in this case are that a lot of devices will
> > >>>>> turn off their controllers when entering display off. And the rest
> > >>>>> when entering sleep. This is good because when you are in dark resume,
> > >>>>> the RGB of the device has turned off. But for [1] it is problematic
> > >>>>> because it assumes the controller works and is what is used to wake
> > >>>>> the device so the mode is broken. For Legion, Sleep is used to turn
> > >>>>> off the controller, and for other devices Sleep Entry/Exit. New in ROG
> > >>>>> Xbox Ally devices is that the controller no longer turns off, but it
> > >>>>> is muted.
> > >>>>>
> > >>>>> The other consideration is that three additional patches are needed
> > >>>>> for ROG Ally devices to work correctly with this series, 2 cleanup
> > >>>>> commits and 1 small delay. But after that it should be drop in. I
> > >>>>> cannot comment on the new hid drivers for Asus and Legion that are
> > >>>>> currently being developed. Particularly, hid-legion-go(?) has a
> > >>>>> reset_resume() cb where it should have used resume? Or not anything?
> > >>>>> The legion controllers save os mode until they disconnect, which they
> > >>>>> do with this series, so the driver would always re-initialize on
> > >>>>> wake-up.
> > >>>>
> > >>>> My rough understanding that a firmware/BIOS update may be needed for
> > >>>> some devices to leverage DSM in regards to power consumption
> > >>>> improvement. Could be true that practically it may not improve much,
> > >>>> will see. Even if not all current devices will benefit from the
> > >>>> screen-off DSM, it may differ for a later generations.
> > >>>
> > >>> Hi Dmitry,
> > >>> sorry, I have been busy the past few days. I read through Rafael's
> > >>> comments, I will respond to them in the next 2-3 days.
> > >>>
> > >>> Your understanding is correct. You will see 0 performance difference
> > >>> with the screen off DSM. It is not supposed to affect the thermal
> > >>> envelope. Turning off the screens of your laptop due to inactivity is
> > >>> not supposed to affect the thermal envelope.
> > >>>
> > >>> For devices that use the DSM to turn off their controller (~60%),
> > >>> there might be a marginal <.5W improvement. The rest use the sleep
> > >>> DSMs for that. Those do affect the thermal envelope. However, they are
> > >>> not designed for prolonged CPU intensive tasks such as a SteamOS
> > >>> download mode. This is the bigger concern. From my experience, I
> > >>> expect the Go S to overheat.
> > >>>
> > >>> The improvement because of turning off the controllers / RGB is
> > >>> something that is needed for download mode in any case. And as my
> > >>> previous comment suggests, lowering the thermal limit may not be
> > >>> required / advantageous.
> > >>
> > >> Here, the sleep dsms are also important, because of their broad
> > >> effects to power light / thermal envelope. As they can be used for
> > >> brief wake / update checks. For battery powered devices, perhaps these
> > >> are not important (excl. hibernation checks), but for desktop consoles
> > >> it is expected functionality.
> > >>
> > >>>>>> A common approach for upstreaming is to divide problem into smaller
> > >>>>>> manageable parts. That's what I'm planning to focus on now to see if we
> > >>>>>> can start easy with a minimal changes.
> > >>>>>
> > >>>>> Sure. One potential approach for this is this series, where the first
> > >>>>> part does the plumbing and the second part the exposing. They can be
> > >>>>> merged independently.
> > >>>>>
> > >>>>> I also made sure to address Rafael's comments, so the ABI of this
> > >>>>> series is completely independent of ACPI, S0ix or whether the device
> > >>>>> has a display. I also removed all references to Intel, AMD specific
> > >>>>> power envelope terminology. Moreover, most of the logic now resides in
> > >>>>> suspend.c and the hooks are in platform_ calls, so it can be
> > >>>>> implemented for other platforms easily.
> > >>>>>
> > >>>>> However, the first part of this series does some refactorings which
> > >>>>> assume a favorable outcome. If we do not want to assume that, a
> > >>>>> simpler initial series would just move the MS/display on/off DSMs to
> > >>>>> .begin() in s2idle.c. If you think that would be easier to merge, you
> > >>>>> are welcome to start with that. Then this series would be refactored
> > >>>>> on top and merged as a single unit. Keep in mind the ROG Ally conflict
> > >>>>> would also arise in this case as well.
> > >>>>>
> > >>>>>> Please don't worry about the credit. You did a significant ground work
> > >>>>>> that is well recognized by now. Thanks a lot for your efforts and help.
> > >>>>>> Starting from scratch of course won't be a good approach with all the
> > >>>>>> broad testing you've done.
> > >>>>>
> > >>>>> Great. Sounds good to me.
> > >>>>
> > >>>> I'm taking latest version of your patches and will update them in
> > >>>> accordance to the review from Rafael.
> > >>>
> > >>> Rafael raised some good questions I need to respond to. Specifically,
> > >>> the ABI is not yet decided, so the comments are not ready to address
> > >>> yet.
> > >>>
> > >>> Nonetheless, this series is ready to test with the current ABI.
> > >>>
> > >>> Moreover, Rafael suggests for upstreaming to follow essentially what I
> > >>> outlined. An initial series should move the DSMs to the beginning of
> > >>> the suspend sequence, and the follow-up would implement the ABI.
> > >>>
> > >>> I was planning to work on the first sub-series as a non-RFC after
> > >>> responding to Rafael's comments. Let me know how you plan to proceed.
> > >
> > > Please go on and make a v2. This version works well with my testing. Thanks!
> >
> > Do you have updates on v2? For now I don't have good suggestion on where
> > to put and how to define standby knobs in sysfs in a more generic
> > manner. Pick what feels better or keep current /sys/power variant with
> > the rest of review comments addressed.
> >
> > Please let me know if help needed,
>
> Hi Dmitry,
> I had some work pop up the past three weeks so I could not go ahead
> with this. I will reprioritize and get back to you with an update by
> end of week.
>
> Here is the current plan for V2. It will consist of four parts.
>
> i) We keep the initial rename patches.
> ii) Then, we move all the calls to the begin() and end() functions.
> After these, we perform a summary cleanup of asus-wmi and hid-asus to
> undo the duplicate handling of the calls due to the prior sequence
> causing issues on Ally devices, and add a small 500ms quirk after the
> begin calls for these devices to resolve a timing issue present on all
> firmwares (the Ally units have a hardcoded ~300ms delay in which they
> fade their RGB before disconnecting the controller and saving its
> state, causing it to reboot on resume if that does not happen; this is
> common in all aura devices such as Asus Keyboards, but no other
> devices cause issues due to the state loss).
>
> These first two parts can merge initially to ensure no issues arise.
>
> Then, we implement the activity API in two parts.
>
> iii) Introduce drivers/acpi/activity.c (match platform profile for
> now), which has an ABI of
> /sys/class/activity/[driver_name]/{name,hint,hint_choices} (non-ACPI
> specific). The ABI and activity.c do not perform state transitions,
> match the platform_profile internal API structure, and are not ACPI
> specific (the file can be moved later).

I note here the use of [driver_name] instead of platform-profile-N,
which should allow basic userspace apps to skip the loop and name
check, hardcoding /sys/class/activity/s2idle/{hint,hint_choices}. In
addition, prefixing the files with hint allows reusing the scaffolding
to implement other ABIs in the future, which would be hard to do with
platform-profile.

For WMI drivers, [driver-name] would include an integer suffix as per
convention for these drivers, with the first instance using 0.

> iv) Register an activity handler in s2idle.c and push the transition
> logic in it. This way, other users do not have to abide by it. If
> userspace is not activity hint aware, enter the state snooze in
> begin(), and restore the prior state in end(). If there is a timing
> quirk (such as for the Ally), we will store the jiffies of the last
> transition and compare them in begin(). This way, when userspace
> becomes activity hint-aware and enters snooze prior to beginning the
> suspend sequence, the delay is shortened. Since userspace freeze by
> the systemd freezer group (if enabled) and then suspend.c require
> around 100ms-300ms, this eats more than half of the delay in this case
> for traditional resume / suspend, and eliminates it for dark screen
> wakeups that remain in snooze.
>
> Antheas
>
>
> > --
> > Best regards,
> > Dmitry
> >