https://bugzilla.kernel.org/show_bug.cgi?id=203529

--- Comment #36 from Andy Shevchenko (andy.shevche...@gmail.com) ---
(In reply to Zhang Rui from comment #31)
> Hi, Andy,
> I'm not quite familiar with how IC2 controller/devices are enumerated.
> 
> But for the current problem,
> 
> OperationRegion (WST1) is located under _SB.PCI0.I2C0, but all the
> firmware_nodes of the I2C0 device are _SB.PCI0.I2C0 child devices. I'm not
> sure what ACPI_COMPANION is, for pci device 00:15.0, and I'm not sure if
> this will make the current I2C code fail to install the address space
> handler for WST1, can you please clarify?

ACPI Companion for 00:15.0 is the device which has _ADR 0x00150000. And
according to ACPI tables it's \_SB.PCI0.I2C0. This represents physical device
that has been split to two inside intel-lpss-pci.c (MFD driver for LPSS
devices). The MFD driver shares firmware node of the parent device with its
children (i.e. iDMA 64-bit and DesignWare I2C drivers). I2C core assigns
address space handler in the case that it's an ACPI enumerated device or device
which has an ACPI companion. So, you need to get sure that
https://elixir.bootlin.com/linux/latest/source/drivers/i2c/i2c-core-acpi.c#L716
is called and called with correct parameters. Perhaps some ACPI debug option
will print you this (I believe ACPICA and ACPI has that kind of options).

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