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

[Antheas Kapenekakis]

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.
>
> Best,
> Antheas
>
> > --
> > Best regards,
> > Dmitry
> >