linux-kernel - Re: [PATCH v4] acpi,pci: warn about duplicate IRQ routing entries returned from

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Date: Fri, 16 Feb 2024 22:19:56 +0100
From: Mateusz Jończyk <mat.jonczyk@...pl>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Bjorn Helgaas <helgaas@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
 Len Brown <lenb@...nel.org>, Jean Delvare <jdelvare@...e.de>,
 Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v4] acpi,pci: warn about duplicate IRQ routing entries
 returned from _PRT

W dniu 16.02.2024 o 21:51, Rafael J. Wysocki pisze:

> On Fri, Feb 16, 2024 at 9:20 PM Mateusz Jończyk <mat.jonczyk@...pl> wrote:
>> W dniu 16.02.2024 o 19:49, Bjorn Helgaas pisze:
>>> On Fri, Feb 16, 2024 at 07:26:06PM +0100, Rafael J. Wysocki wrote:
>>>> On Tue, Dec 26, 2023 at 1:50 PM Mateusz Jończyk <mat.jonczyk@...pl> 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.
>>>>>
>>>>> As a debugging aid, print a warning to dmesg if duplicate interrupt
>>>>> routing entries are present. This way, we could check how many models
>>>>> are affected.
>>>>>
>>>>> This happens on a Dell Latitude E6500 laptop with the i2c-i801 Intel
>>>>> SMBus controller. This controller is nonfunctional unless its interrupt
>>>>> usage is disabled (using the "disable_features=0x10" module parameter).
>>>>>
>>>>> After investigation, it turned out that the driver was using an
>>>>> incorrect interrupt vector: in lspci output for this device there was:
>>>>>         Interrupt: pin B routed to IRQ 19
>>>>> but after running i2cdetect (without using any i2c-i801 module
>>>>> parameters) the following was logged to dmesg:
>>>>>
>>>>>         [...]
>>>>>         i801_smbus 0000:00:1f.3: Timeout waiting for interrupt!
>>>>>         i801_smbus 0000:00:1f.3: Transaction timeout
>>>>>         i801_smbus 0000:00:1f.3: Timeout waiting for interrupt!
>>>>>         i801_smbus 0000:00:1f.3: Transaction timeout
>>>>>         irq 17: nobody cared (try booting with the "irqpoll" option)
>>>>>
>>>>> Existence of duplicate entries in a table returned by the _PRT method
>>>>> was confirmed by disassembling the ACPI DSDT table.

[snip]

>>> And neither of the two _PRT entries yields a working i801 device?
>> Unpatched Linux uses the first matching entry, but the second one gives
>> a working i801 device. The point is to print a warning message to see
>> how many devices are affected and whether it is safe to switch the code
>> to use the last matching entry in all instances.
>>
>> Therefore I used dev_warn().
> I don't quite see a connection between the above and the log level.

OK, so I'll use dev_info() then.

Greetings,
Mateusz