Re: [REGRESSION][BISECTED] Lenovo IdeaPad touchpad does not work when idma64 is present in initramfs

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Dec 16, 2025 at 12:57:10PM -0500, correctmost wrote:

> The following commit

No, it's false positive. The reality is that something else is going on
there on this and other similar laptops.

> causes my Lenovo IdeaPad touchpad not to work when
> kernel/drivers/dma/idma64.ko.zst is present in the initramfs image:
> 
> #regzbot introduced: 9140ce47872bfd89fca888c2f992faa51d20c2bc
> 
> "idma64: Don't try to serve interrupts when device is powered off"

So, the touchpad is an I²C device, which is connected to an Intel SoC.
The I²C host controller is Synopsys DesignWare. On Intel SoCs the above
mentioned IP is generated with private DMA engine, that's called Intel
iDMA 64-bit. Basically it's two devices under a single PCI hood.
The problem here is that when PCI device is in D3, both devices are
powered off, but something sends an interrupt and it's not recognized
being the one, send by a device (touchpad).

There is one of the following potential issues (or their combinations):

- the I²C host controller hardware got off too early
- the line is shared with something else that generates interrupt storm
- the BIOS does weird (wrong) things at a boot time, like not properly
  shutting down and disabling interrupt sources; also may have wrong
  pin control settings
- the touchpad is operating on higher frequency like 400kHz (because
  BIOS told to use that one instead of 100kHz) than the HW is designed
  for and hence unreliable with all possible side effects
- the touchpad firmware behaves wrongly on some sequences (see also
  note about the bus speed above), try to upgrade touchpad FW

With my experience with the case of the above mentioned commit that it
may be BIOS thingy. Also consider the bus speed, there are quirks in
the kernel for that.

> Here are the related logs:
> 
> ---
> 
> irq 27: nobody cared (try booting with the "irqpoll" option)

Almost all below is not so interesting.

...

> handlers:
> [<00000000104a7621>] idma64_irq [idma64]
> [<00000000bd8d08e9>] i2c_dw_isr
> Disabling IRQ #27

Yes, this line at least shared between those two and might be more.

...

> i2c_designware i2c_designware.0: controller timed out
> hid (null): reading report descriptor failed
> i2c_hid_acpi i2c-ELAN06FA:00: can't add hid device: -110
> i2c_hid_acpi i2c-ELAN06FA:00: probe with driver i2c_hid_acpi failed with error -110

Yes, sounds familiar with the speed settings. Try to down it to 100kHz in case
it's confirmed to be 400kHz.

> ---
> 
> Hardware info:
> - Lenovo 16" IdeaPad Slim 5 - 16IRU9
>   - Hardware name: LENOVO 83FW/LNVNB161216, BIOS PFCN14WW 09/20/2024
>   - ELAN06FA:00 04F3:327E Touchpad
> 
> Steps to reproduce:
> - Cold boot the laptop on Arch Linux
> 
> The bug is still present with the 6.19.0-rc1-1-git kernel.
> 
> The bisected commit is from March 2024, but I only recently noticed the issue
> because the initramfs images on Arch Linux now include these additional
> drivers (as of November 2025):
> - kernel/drivers/dma/idma64.ko.zst
> - kernel/drivers/mfd/intel-lpss-pci.ko.zst
> - kernel/drivers/mfd/intel-lpss.ko.zst
> 
> Two other users have reported the issue on the Arch Linux and CachyOS forums,

Any pointers to that thread, please?

> so I don't think this is a hardware issue with my individual laptop.

I don't know how this conclusion is came here. You mean HW as laptop model?
But are the involved components the same (I²C host controller + touchpad)?

-- 
With Best Regards,
Andy Shevchenko