Message-ID: <75db5770-fe31-4569-bab5-1f259223506e@gmx.de>
Date:   Tue, 28 Nov 2023 02:16:53 +0100
From:   Armin Wolf <W_Armin@....de>
To:     Luke Jones <luke@...nes.dev>
Cc:     Mario Limonciello <mario.limonciello@....com>, hdegoede@...hat.com,
        ilpo.jarvinen@...ux.intel.com, corentin.chary@...il.com,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] platform/x86: asus-wmi: disable USB0 hub on ROG
 Ally before suspend

Am 28.11.23 um 01:54 schrieb Luke Jones:

>
>
> On Mon, Nov 27 2023 at 10:42:48 PM +01:00:00, Armin Wolf
> <W_Armin@....de> wrote:
>> Am 27.11.23 um 21:55 schrieb Mario Limonciello:
>>> On 11/27/2023 14:46, Luke Jones wrote:
>>>>
>>>>
>>>>  On Mon, Nov 27 2023 at 02:14:23 PM -06:00:00, Mario Limonciello
>>>> <mario.limonciello@....com> wrote:
>>>>> On 11/26/2023 17:05, Luke D. Jones wrote:
>>>>>> ASUS have worked around an issue in XInput where it doesn't
>>>>>> support USB
>>>>>>  selective suspend, which causes suspend issues in Windows. They
>>>>>> worked
>>>>>>  around this by adjusting the MCU firmware to disable the USB0
>>>>>> hub when
>>>>>>  the screen is switched off during the Microsoft DSM suspend path
>>>>>> in ACPI.
>>>>>>
>>>>>>  The issue we have with this however is one of timing - the call
>>>>>> the tells
>>>>>>  the MCU to this isn't able to complete before suspend is done so
>>>>>> we call
>>>>>>  this in a prepare() and add a small msleep() to ensure it is
>>>>>> done. This
>>>>>>  must be done before the screen is switched off to prevent a
>>>>>> variety of
>>>>>>  possible races.
>>>>>
>>>>>  Right now the way that Linux handles the LPS0 calls is that
>>>>> they're all back to back.  Luke did try to inject a delay after
>>>>> the LPS0 calls were done but before it went to sleep but this
>>>>> wasn't sufficient.
>>>>>
>>>>>  Another "potential" way to solve this problem from Linux may be
>>>>> to actually glue the LPS0 screen off call to when DRM actually has
>>>>> eDP turned off.
>>>>>
>>>>>  Making such a change would essentially push back the "screen off"
>>>>> LPS0 command to when the user has run 'systemctl suspend' (or an
>>>>> action that did this) because the compositor usually turns it off
>>>>> with DPMS at this time.
>>>>
>>>>  I would be willing to test this if you want some concrete data.
>>>
>>>  It would require some cross subsystem plumbing to evaluate
>>> feasibility.
>>>  I don't currently have any plans to do it.
>>>
>>>  I think your patch makes sense; I just want to make it known that
>>> "might" clean this up if it ever happens.
>>>
>>>> See my big block of text below.
>>>>
>>>>>
>>>>>  This is a much bigger change though and *much more ripe for
>>>>> breakage*.
>>>>>
>>>>>  So I think in may be worth leaving a TODO comment to look into
>>>>> doing that in the future.
>>>>  Do you mean add the TODO to a line in this patch?
>>>
>>>  Yeah.  In case someone ever does it (me or otherwise) I think it
>>> would be good to have some reference in the comments that the commit
>>> 'might' be possible to revert.
>>>
>>>>
>>>>>
>>>>>  If that ever happens; it's possible that this change could be
>>>>> reverted too.
>>>>>
>>>>>>
>>>>>>  Further to this the MCU powersave option must also be disabled
>>>>>> as it can
>>>>>>  cause a number of issues such as:
>>>>>>  - unreliable resume connection of N-Key
>>>>>>  - complete loss of N-Key if the power is plugged in while suspended
>>>>>>  Disabling the powersave option prevents this.
>>>>>>
>>>>>>  Without this the MCU is unable to initialise itself correctly on
>>>>>> resume.
>>>>>
>>>>>  initialize
>>>>
>>>>  Are we forced to use USA spelling? I'm from NZ
>>>>  "initialise is predominantly used in British English (used in
>>>> UK/AU/NZ) ( en-GB )"
>>>>
>>>
>>>  Ah I didn't realize it's an acceptable spelling for en-GB, and
>>> thought it was just a typo; sorry.
>>>
>>>>>
>>>>>>
>>>>>>  Signed-off-by: Luke D. Jones <luke@...nes.dev>
>>>>>
>>>>>  I think it would be good to add a Closes: tag to the AMD Gitlab
>>>>> issue that this was discussed within as well as any other public
>>>>> references you know about.
>>>>>
>>>>>  Additionally as Phoenix APU support goes back as far as kernel
>>>>> 6.1 and this is well contained to only run on the ROG I suggest to
>>>>> CC stable so that people can use the ROG on that LTS kernel or later.
>>>>>
>>>>>> ---
>>>>>>  -SNIP-
>>>>>>    @@ -4701,6 +4749,8 @@ static const struct dev_pm_ops
>>>>>> asus_pm_ops = {
>>>>>>        .thaw = asus_hotk_thaw,
>>>>>>        .restore = asus_hotk_restore,
>>>>>>        .resume = asus_hotk_resume,
>>>>>>  +    .resume_early = asus_hotk_resume_early,
>>>>>>  +    .prepare = asus_hotk_prepare,
>>>>>
>>>>>  Have you experimented with only using the prepare() call or only
>>>>> the resume_early() call?  Are both really needed?
>>>>
>>>>  I have yes. Although the device comes back eventually in resume
>>>> after only a prepare call it's not preferable as it tends to change
>>>> the device path. With resume_early we can get the device replugged
>>>> super early (before anything notices it's gone in fact).
>>>>
>>>>  This whole thing is a bit of a mess. It ends up being a race
>>>> between various things to prevent a HUB0 disconnect being
>>>> registered by the xhci subsystem, and adding the device back before
>>>> the xhci subsystem gets control.
>>>>
>>>>  If I add a sleep longer than 1300ms in prepare then the xhci
>>>> subsys registers a disconnect of the USB0 hub. If the sleep is
>>>> under 250ms it isn't quite enough for the MCU to do its thing, and
>>>> on battery it seems worse.
>>>>
>>>>  I have asked the ASUS guys I'm in contact with for something to
>>>> disable this MCU behaviour since it is purely a workaround for a
>>>> broken Windows thing :( They are open to something, maybe an OS
>>>> detect in ACPI or a WMI method addition similar to the MCU
>>>> powersave method, from what I'm told it would require an MCU
>>>> firmware update along with BIOS update. If this eventuates I'll
>>>> submit an additional patch to check and set that plus disable this.
>>>
>>>  Don't let them do an OS detection in ACPI, it's going to be too
>>> painful.
>>>  I would instead suggest that they can have a bit that you can
>>> program in via ACPI or WMI from the ASUS WMI driver that says to
>>> skip the MCU disconnect behavior.
>>>
>> I totally agree, we do not need another _OSI(Linux) type of problem.
>> Maybe those guys at Asus could just implement a ACPI _DSM for the USB
>> controller in question which allows for disabling this workaround.
>> This would be preferable to an additional WMI method, since the
>> notebook would otherwise depend on the asus-wmi driver to suspend
>> properly.
>> With the ACPI _DSM, the USB controller driver can disable the
>> workaround as soon as the USB controller probes.
>
> Would you be so kind as to explain what this means? My knowledge of
> ACPI is paper thin and generally revolves just around the ASUS WMI
> part. From what i can find the XHC0 (the hub the MCU is attached to)
> doesn't have any current _DSM. I understand it means Device Specific
> Method, so I guess you mean adding a method to be used only if that
> HUB is there and implements it?
>
> The ROG Ally depends on the asus-wmi driver regardless, without it, it
> is barely functional.
>
An ACPI _DSM method is a "standardized" way for manufacturers to add device specific methods to ACPI devices, see
https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/09_ACPI-Defined_Devices_and_Device-Specific_Objects/ACPIdefined_Devices_and_DeviceSpecificObjects.html for details.

Implementing via a ACPI _DSM would contain the necessary logic for USB suspend inside the USB hub driver, instead of forcing asus-wmi and the USB hub driver
to collaborate on USB suspend. The USB hub driver would discover this device specific method during probe and disable the workaround, leaving no chance for
race conditions between asus-wmi and the USB hub driver to develop.

Of course if the ROG Ally depends on asus-wmi regardless, then Asus could as well use the WMI interface for this. But IMHO standard ACPI interfaces should be
preferred to custom ones like WMI.

Armin Wolf

>>>>
>>>>  I may possibly write a new version of this patch as we've seen
>>>> that enabling powersave reduces suspend power use by at least half.
>>>> And looking through my DSDT dumps, there are a few laptops with the
>>>> same feature as Ally. The patch for powersave being enabled
>>>> requires also AC power state on suspend change detection, and a
>>>> later forced reset in late resume (and the device paths change
>>>> regardless when powersave is on).
>>>>
>>>>  When I look at it objectively, the device path changing should be
>>>> a non-issue really as it is fully handled by USB subsystem and
>>>> behaves exactly like what it is - a USB hub disconnect. It's just
>>>> that some userspace apps don't expect this. I will experiment some
>>>> more.
>>>>
>>>>  Regards,
>>>>  Luke.
>>>>
>>>
>>>  As another experiment - what happens if you "comment out" the LPS0
>>> calls that do this problematic stuff?
>>>
>>>  It's important to make sure the callback to amd-pmc stays in place,
>>> but if you just skip those ACPI ones does it still get to the
>>> deepest state and are there other problems?
>>>
>>>>>
>>>>>>   };
>>>>>>      /* Registration
>>>>>> ***************************************************************/
>>>>>>  diff --git a/include/linux/platform_data/x86/asus-wmi.h
>>>>>> b/include/linux/platform_data/x86/asus-wmi.h
>>>>>>  index 63e630276499..ab1c7deff118 100644
>>>>>>  --- a/include/linux/platform_data/x86/asus-wmi.h
>>>>>>  +++ b/include/linux/platform_data/x86/asus-wmi.h
>>>>>>  @@ -114,6 +114,9 @@
>>>>>>    /* Charging mode - 1=Barrel, 2=USB */
>>>>>>    #define ASUS_WMI_DEVID_CHARGE_MODE    0x0012006C
>>>>>>    +/* MCU powersave mode */
>>>>>>  +#define ASUS_WMI_DEVID_MCU_POWERSAVE   0x001200E2
>>>>>>  +
>>>>>>    /* epu is connected? 1 == true */
>>>>>>    #define ASUS_WMI_DEVID_EGPU_CONNECTED    0x00090018
>>>>>>    /* egpu on/off */
>>>>>
>>>>
>>>>
>>>
>>>
>
>
>

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