Re: i2c designware change broke touchpad of a thinkpad

Thanks for the detailed background, Thorsten and Hans.

Confirming I'm now on this thread. For reference, the bug I reported
(deferred probe on both i2c_designware.0 and .1, ELAN0307 touchpad
never coming up) is tracked here:
https://bugzilla.kernel.org/show_bug.cgi?id=221889

With Linus's revert (d5b95e612cde) applied on top of 7.2 final, my
system is working correctly again — both i2c_designware controllers
probe successfully (~2.80s), the touchpad registers via hid-multitouch,
and /sys/kernel/debug/devices_deferred is empty.

Happy to test Hardik's upcoming i2c-hid-core patch (the IRQ-request-
before-connectivity-check approach Hans described) on this hardware
once it's ready, and report back whether it resolves the original
issue without reintroducing the deferred-probe regression.

Let me know when there's something to test.

Best regards,
Tran Tien Dat


Vào Thứ 2, 17 thg 8, 2026 vào lúc 18:12 Thorsten Leemhuis
<[email protected]> đã viết:
>
> On 8/17/26 11:51, [email protected] wrote:
> > On 14-Aug-26 12:09 PM, Hardik Prakash wrote:
> >> On Wed, 13 Aug 2026, Thorsten Leemhuis wrote:
> >>> Hardik, could you submit a revert to the lists? And then I'll provide my
> >>> Tested-by and ask Linus to directly pick this up?
> >>
> >> Sent: https://lore.kernel.org/all/[email protected]/
> >>
> >> Verified on my end that it builds clean, boots clean, and correctly
> >> restores the original Yoga 7 race (expected tradeoff) without
> >> introducing anything else.
>
> Hans, thx for looking into this.
> > Thank you for submitting a revert for this. Note it looks like Torvalds himself
> > beat you to it and already reverted this for 7.2 final :)
>
> Yeah, I pointed Linus to this and a few others issues and then he
> reverted the change directly:
> https://lore.kernel.org/all/[email protected]/
>
> > I hit another problem caused by this now reverted change, where the PMIC
> > i2c bus would not show up on many Intel BYT/CHT devices. I wrote a fix for
> > this (attached) on top of the now reverted commit.
>
> FWIW, meanwhile "Tran Tien Dat" (now CCed) with -next ran into a problem
> on a MSI Modern 14 H D13MG that the revert seems to have resolved. But
> the symptoms were different: the two DesignWare I2C controllers in that
> machine apparently deferred probe forever and are never retried:
>
> 16.429266 platform i2c_designware.1: deferred probe pending: (reason
> unknown)
> 16.429286 platform i2c_designware.0: deferred probe pending: (reason
> unknown)
>
> For details, see: https://bugzilla.kernel.org/show_bug.cgi?id=221889
>
> Ciao, Thorsten
>
> > I think my fix might also have helped for the broken touchpad issue from this
> > thread, but I believe there is a better way to fix all this, so IMHO it is
> > good that this was reverted.
> >
> > If I understand things correctly the problem the reverted fix was trying
> > to fix is i2c-transfer errors happening before the GPIO controller driver
> > is ready.
> >
> > The i2c-core will not initiate transfers itself, so the problem is that
> > the i2c-hid driver is initiating transfers before the GPIO controller
> > is setup.
> >
> > The i2c-hid driver does actually request the interrupt itself, so we can
> > simply wait for that to succeed inside the i2c-hid code. ATM the i2c-hid
> > code starts with an i2c-connectivity check because some ACPI tables list
> > non existing I2C-HID devices.
> >
> > But we could make the i2c-hid driver start with first requesting its IRQ
> > and if that fails bail (with -EPROBE_DEFER) before doing any i2c-transfers.
> >
> > And then do the i2c-connectivity test after requesting the IRQ. So basically
> > swap the order of i2c-connectivity test vs IRQ requesting.
> >
> > The IRQ requesting should then use the IRQF_NO_AUTOEN flag to keep the IRQ
> > disabled at first and explicitly enable it later when the rest of the driver
> > setup is done.
> >
> > Hardik, can you take a shot at coding up the suggested i2c-hid(-core) changes
> > and test to see if this fixes the original Yoga 7 race in a cleaner manner ?
> >
> > Regards,
> >
> > Hans
> >
>