Re: i2c designware change broke touchpad of a thinkpad

On Wed, 12 Aug 2026, Thorsten Leemhuis wrote:
> While we wait for Mario a quick question: Should we revert
> the culprit for 7.2 and reapply it later once we sorted this out? Of
> course I'll continue to help debugging this.
>
> If it was just me I'd say "don't bother", but these kind of Thinkpads
> are what some Linux users frequently buy, so I fear that other people
> will run into this if the culprit makes it into 7.2.

I agreed, I'd rather have this reverted than ship a known regression.

Andi, WSA -- given 7.2 is close, could this go out as a revert now? I'll
keep working the AMD bus-timing angle with Thorsten and Mario, and
we can resubmit a corrected fix for a later release once it's actually
understood.

Thanks,
Hardik

On Wed, 12 Aug 2026 at 10:51, Thorsten Leemhuis
<[email protected]> wrote:
>
> On 8/12/26 06:59, Hardik Prakash wrote:
> > On Mon, 10 Aug 2026, Thorsten Leemhuis wrote:
> >> Did a fresh boot and uploaded the dmesg again as well just in case:
> >> https://www.leemhuis.info/files/misc/dmesg_patch_dyndbg2
> >> https://www.leemhuis.info/files/misc/lsmod
> >> https://www.leemhuis.info/files/misc/interrupts
> >
> > Thanks. Second boot reproduces the identical pattern: device_is_bound()
> > =true at 1.132s, lost arbitration at 2.139s -- same ~1s gap as the first
> > capture, so this is consistent and reproducible, not a one-off.
> >
> > interrupts rules out simple IRQ-line sharing: AMDI0010:01 has its own
> > dedicated line (IRQ 11), separate from AMDI0010:00 (IRQ 10) and every
> > amd_gpio ACPI:Event line. psp-1 exists (IR-PCI-MSIX-0000:c3:00.2) but
> > shows zero recorded activity on any CPU.
> >
> > Since lost arbitration means an actual SDA/SCL-level collision (not an
> > IRQ conflict), and there's no shared IRQ or visible PSP activity, if
> > something else is touching this bus it's happening below what Linux's
> > interrupt accounting can see -- which is why I wanted your take, Mario.
> > Does this match a known pattern of firmware (PSP/EC) briefly taking
> > this bus during boot on AMD platforms?
>
> Thx again. While we wait for Mario a quick question: Should we revert
> the culprit for 7.2 and reapply it later once we sorted this out? Of
> course I'll continue to help debugging this.
>
> If it was just me I'd say "don't bother", but these kind of Thinkpads
> are what some Linux users frequently buy, so I fear that other people
> will run into this if the culprit makes it into 7.2.
>
> Ciao, Thorsten
>
> > On Mon, 10 Aug 2026 at 12:18, Thorsten Leemhuis <[email protected]> wrote:
> >>
> >> On 8/10/26 07:54, Hardik Prakash wrote:
> >>> On Sun, 9 Aug 2026, Thorsten Leemhuis wrote:
> >>>> Sorry, picked the wrong file while preparing the mail, it's here:
> >>>> https://www.leemhuis.info/files/misc/dmesg_patch_dyndbg
> >>>
> >>> Thanks, that's the one. Full timeline from that boot:
> >>>
> >>>   0.619s  AMDI0010:00 and AMDI0010:01 defer (AMDI0030:00 not registered)
> >>>   1.136s  Retry succeeds: device_is_bound()=true for AMDI0030:00,
> >>>           confirmed for all three children (XXXX0000:00, SYNA8018:00,
> >>>           NXP1001:00)
> >>>   2.222s  lost arbitration on AMDI0010:01 (x3)
> >>>   3.260s  controller timed out, HID descriptor fetch fails
> >>>
> >>> The dependency check itself is behaving correctly here -- it defers,
> >>> then correctly confirms AMDI0030:00 is bound before letting probe
> >>> continue. The arbitration failure happens over a second *after* that,
> >>> when the touchpad attempts its actual first transaction.
> >>>
> >>> So this doesn't look like a logic bug in the check itself. My read: by
> >>> delaying dw_i2c_plat_probe() by ~500ms (correctly, for GPIO's sake),
> >>> something else ends up contending for the AMDI0010:01 bus by the time
> >>> the touchpad's first transaction actually happens -- a window that
> >>> the original (undeferred, earlier) probe attempt apparently avoided.
> >>>
> >>> Mario -- does this look like a known AMD I2C/PSP semaphore contention
> >>> pattern to you? Wondering if there's a shared bus/firmware consumer
> >>> that could explain a ~1s-later collision like this, independent of
> >>> the GPIO controller itself being ready.
> >>>
> >>> Thorsten, if you have it handy: /proc/interrupts and lsmod from this
> >>> boot would help narrow down what else might be touching that bus
> >>> around the 2.2s mark.
> >>
> >> Did a fresh boot and uploaded the dmesg again as well just in case:
> >>
> >> https://www.leemhuis.info/files/misc/dmesg_patch_dyndbg2
> >> https://www.leemhuis.info/files/misc/lsmod
> >> https://www.leemhuis.info/files/misc/interrupts
> >>
> >> Ciao, Thorsten
> >>> On Mon, 10 Aug 2026 at 11:06, Thorsten Leemhuis <[email protected]> wrote:
> >>>>
> >>>> On 8/10/26 07:23, Hardik Prakash wrote:
> >>>>> On Sat, 8 Aug 2026, Thorsten Leemhuis wrote:
> >>>>>> https://www.leemhuis.info/files/misc/dmesg-master-plus_revert
> >>>>>>
> >>>>>> [    0.619018] i2c-dw-gpio-dbg: i2c_dw_check_gpio_dependencies(AMDI0010:00)
> >>>>>> [...]
> >>>>>> [    1.136010] i2c-dw-gpio-dbg: device_is_bound()=true for AMDI0030:00
> >>>>>
> >>>>> Thanks, this trace looks correct on its face (defer at 0.619s, retry
> >>>>> succeeds at 1.122-1.136s), but the link above points to the same file
> >>>>> you sent last round (the master+revert baseline, no debug patch, no
> >>>>> i2c-dw-gpio-dbg lines in it at all) rather than this new capture.
> >>>>>> Could you share the full, unfiltered dmesg from this exact boot (the
> >>>>> one with the debug patch applied)? I need to see where
> >>>>> "lost arbitration" falls relative to the trace above.
> >>>>
> >>>> Sorry, picked the wrong file while preparing the mail, it's here:
> >>>> https://www.leemhuis.info/files/misc/dmesg_patch_dyndbg
> >>>>
> >>>> Ciao, Thorsten
> >>>>
> >>>>> Separately, from your DSDT: NFC1 (NXP1001), which shows up as a child
> >>>>> of AMDI0010:01 in your trace, declares its _CRS as a raw resource
> >>>>> buffer containing three GPIO resources referencing \_SB.GPIO -- one
> >>>>> GpioIo and two separate GpioInt entries. Not sure yet if that's
> >>>>> relevant, but it's a pattern I haven't seen on my hardware
> >>>>> which I've tested against.
> >>>>>
> >>>>> Thanks,
> >>>>> Hardik
> >>>>>
> >>>>> On Sun, 9 Aug 2026 at 21:49, Thorsten Leemhuis <[email protected]> wrote:
> >>>>>>
> >>>>>> On 8/8/26 22:25, Andy Shevchenko wrote:
> >>>>>>> On Sat, Aug 08, 2026 at 10:31:28PM +0530, Hardik Prakash wrote:
> >>>>>>>> On Fri, 7 Aug 2026, Thorsten Leemhuis wrote:
> >>>>>>>>> This became 0a4bb2abc3e56d ("i2c: designware: defer probe if child
> >>>>>>>>> GpioInt controllers are not bound") and causes a regression for me: the
> >>>>>>>>> Touchpad in my ThinkPad T14s Gen 4 (AMD) stopped working. From the
> >>>>>>>>> kernel log:
> >>>>>>>>>
> >>>>>>>>> i2c_designware AMDI0010:01: i2c_dw_handle_tx_abort: lost arbitration
> >>>>>>>>> i2c_designware AMDI0010:01: controller timed out
> >>>>>>>>> i2c_hid_acpi i2c-SYNA8018:00: failed to fetch HID descriptor: -110
> >>>>>>>>> i2c_hid_acpi i2c-SYNA8018:00: Failed to fetch the HID Descriptor
> >>>>>>>>>
> >>>>>>>>> Reverting this change in current mainline/master (f9a2394a23482) fixed
> >>>>>>>>> things for me. Full dmesg of current master and master+revert can be
> >>>>>>>>> found here:
> >>>>>>>>>
> >>>>>>>>> https://www.leemhuis.info/files/misc/dmesg-master
> >>>>>>>>> https://www.leemhuis.info/files/misc/dmesg-master-plus_revert
> >>>>>>>> [...]
> >>>>>>>> Two things that would help narrow this down, whenever you have a moment:
> >>>>>>
> >>>>>> Thx for looking into this. Here we go:
> >>>>>>
> >>>>>>>> 1. A DSDT dump
> >>>>>>
> >>>>>> https://www.leemhuis.info/files/misc/dsdt.dsl
> >>>>>>
> >>>>>>>> 2. A dmesg with dynamic debug from a kernel built with the attached
> >>>>>>>>    patch on top of current mainline/master
> >>>>>>
> >>>>>> https://www.leemhuis.info/files/misc/dmesg-master-plus_revert
> >>>>>>
> >>>>>> [    0.619018] i2c-dw-gpio-dbg: i2c_dw_check_gpio_dependencies(AMDI0010:00)
> >>>>>> [    0.619018] i2c-dw-gpio-dbg: check_child_gpioint(adev=XXXX0000:00)
> >>>>>> [    0.619076] i2c-dw-gpio-dbg: GpioInt resource_source=\_SB.GPIO (len=10)
> >>>>>> [    0.619079] i2c-dw-gpio-dbg: acpi_fetch_acpi_dev() succeeded,
> >>>>>> device=AMDI0030:00
> >>>>>> [    0.619080] i2c-dw-gpio-dbg: gpio_device_find_by_fwnode() returned
> >>>>>> NULL, deferring
> >>>>>> [    0.619082] i2c-dw-gpio-dbg: check_child_gpioint ret=-517 (defer)
> >>>>>> [    0.619102] i2c-dw-gpio-dbg: i2c_dw_check_gpio_dependencies(AMDI0010:01)
> >>>>>> [    0.619104] i2c-dw-gpio-dbg: check_child_gpioint(adev=SYNA8018:00)
> >>>>>> [    0.619159] i2c-dw-gpio-dbg: GpioInt resource_source=\_SB.GPIO (len=10)
> >>>>>> [    0.619162] i2c-dw-gpio-dbg: acpi_fetch_acpi_dev() succeeded,
> >>>>>> device=AMDI0030:00
> >>>>>> [    0.619162] i2c-dw-gpio-dbg: gpio_device_find_by_fwnode() returned
> >>>>>> NULL, deferring
> >>>>>> [    0.619164] i2c-dw-gpio-dbg: check_child_gpioint ret=-517 (defer)
> >>>>>> [    1.122517] i2c-dw-gpio-dbg: i2c_dw_check_gpio_dependencies(AMDI0010:00)
> >>>>>> [    1.122523] i2c-dw-gpio-dbg: check_child_gpioint(adev=XXXX0000:00)
> >>>>>> [    1.122625] i2c-dw-gpio-dbg: GpioInt resource_source=\_SB.GPIO (len=10)
> >>>>>> [    1.122636] i2c-dw-gpio-dbg: acpi_fetch_acpi_dev() succeeded,
> >>>>>> device=AMDI0030:00
> >>>>>> [    1.122639] i2c-dw-gpio-dbg: gpio_device_find_by_fwnode() succeeded
> >>>>>> [    1.122642] i2c-dw-gpio-dbg: device_is_bound()=true for AMDI0030:00
> >>>>>> [    1.135894] i2c-dw-gpio-dbg: i2c_dw_check_gpio_dependencies(AMDI0010:01)
> >>>>>> [    1.135898] i2c-dw-gpio-dbg: check_child_gpioint(adev=SYNA8018:00)
> >>>>>> [    1.135976] i2c-dw-gpio-dbg: GpioInt resource_source=\_SB.GPIO (len=10)
> >>>>>> [    1.135980] i2c-dw-gpio-dbg: acpi_fetch_acpi_dev() succeeded,
> >>>>>> device=AMDI0030:00
> >>>>>> [    1.135983] i2c-dw-gpio-dbg: gpio_device_find_by_fwnode() succeeded
> >>>>>> [    1.135985] i2c-dw-gpio-dbg: device_is_bound()=true for AMDI0030:00
> >>>>>> [    1.135987] i2c-dw-gpio-dbg: check_child_gpioint(adev=NXP1001:00)
> >>>>>> [    1.136005] i2c-dw-gpio-dbg: GpioInt resource_source=\_SB.GPIO (len=10)
> >>>>>> [    1.136008] i2c-dw-gpio-dbg: acpi_fetch_acpi_dev() succeeded,
> >>>>>> device=AMDI0030:00
> >>>>>> [    1.136009] i2c-dw-gpio-dbg: gpio_device_find_by_fwnode() succeeded
> >>>>>> [    1.136010] i2c-dw-gpio-dbg: device_is_bound()=true for AMDI0030:00
> >>>>>>
> >>>>>> HTH, Ciao, Thorsten
> >>>>>>
> >>>>>>>> On Fri, 7 Aug 2026 at 19:37, Thorsten Leemhuis <[email protected]> wrote:
> >>>>>>>>> On 7/28/26 10:30, Andi Shyti wrote:
> >>>>>>>>>> On Sat, Jul 18, 2026 at 11:13:31AM +0530, Hardik Prakash wrote:
> >>>>>>>>>>> I2C controllers may have child devices with GpioInt resources that
> >>>>>>>>>>> depend on GPIO controllers being fully initialized. If the I2C
> >>>>>>>>>>> controller probes and enumerates children before the referenced GPIO
> >>>>>>>>>>> controller has completed probe, GPIO interrupts may not be properly
> >>>>>>>>>>> configured, leading to device failures.
> >>>>>>>>>>>
> >>>>>>>>>>> On Lenovo Yoga 7 14AGP11, the WACF2200 touchscreen (child of
> >>>>>>>>>>> AMDI0010:02) has a GpioInt resource pointing to GPIO 157 on the
> >>>>>>>>>>> pinctrl-amd controller (AMDI0030:00). When i2c-designware probes
> >>>>>>>>>>> AMDI0010:02 before pinctrl-amd finishes initializing, I2C transactions
> >>>>>>>>>>> fail with lost arbitration errors:
> >>>>>>>>>>>
> >>>>>>>>>>>   0.285952  amd_gpio_probe: registering gpiochip  <- GPIO chip visible
> >>>>>>>>>>>   0.287121  amd_gpio_probe: requesting parent IRQ <- probe still running
> >>>>>>>>>>>   0.301454  AMDI0010:02 dw_i2c_plat_probe: start  <- races here
> >>>>>>>>>>>   2.348157  lost arbitration
> >>>>>>>>>>>
> >>>>>>>>>>> Add a dependency check that walks ACPI child devices and defers probe
> >>>>>>>>>>> until any referenced GPIO controller is bound.
> >>>>>>>
> >>>>>>> [...]
> >>>>>>>
> >>>>>>>>> #regzbot introduced: 0a4bb2abc3e56d
> >>>>>>>>> #regzbot title i2c: designware: ThinkPad touchpad broke
> >>>>>>>
> >>>>>>
> >>>>>
> >>>>
> >>>
> >>
> >
>