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

[Dmitry Osipenko]

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!

-- 
Best regards,
Dmitry