Re: [PATCH v2] acpi,pci: handle duplicate IRQ routing entries returned from _PRT

Mateusz Jończyk
2022-11-12T20:14:03Z

W dniu 12.11.2022 o 01:20, Bjorn Helgaas pisze:
> [+cc Jean, linux-i2c]
>
> On Sat, Sep 17, 2022 at 11:09:44AM +0200, Mateusz Jończyk wrote:
>> On some platforms, the ACPI _PRT function returns duplicate interrupt
>> routing entries. Linux uses the first matching entry, but sometimes the
>> second matching entry contains the correct interrupt vector.
> Rafael, Jean, what do you think about this? It seems like kind of a
> lot of infrastructure to deal with this oddness, but I'm not really
> opposed to it.
>
> This is in i2c-i801.c, which seems to have some support for polling;
> maybe it could make smart enough to complain and automatically switch
> to polling if a timeout occurs.
>
> Or maybe we scan the entire _PRT and let the match win (instead of the
> first as we do today).
>
> Or ...?
>
> Google finds a lot of hits for "i801_smbus" "timeout waiting for
> interrupt", but I can't tell whether they're a similar _PRT issue or
> something else.
>
>> This happens on a Dell Latitude E6500 laptop with the i2c-i801 Intel
>> SMBus controller. This controller was nonfunctional unless its interrupt
>> usage was disabled (using the "disable_features=0x10" module parameter).

Hello,

I have prepared a lean patch that only prints a warning when there are
two matching entries in the table returned from _PRT (I will send it in the
next e-mail). Perhaps it could be merged and then after a release or two
it will be known how widespread this problem is.

Greetings,

Mateusz