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

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Message-ID: <20240213223908.435aec7b@endymion.delvare>
Date: Tue, 13 Feb 2024 22:39:08 +0100
From: Jean Delvare <jdelvare@...e.de>
To: Mateusz Jończyk <mat.jonczyk@...pl>
Cc: linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org, Bjorn Helgaas
 <bhelgaas@...gle.com>, "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown
 <lenb@...nel.org>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH v4] acpi,pci: warn about duplicate IRQ routing entries
 returned from _PRT

Hi Mateusz,

On Tue, 26 Dec 2023 13:42:54 +0100, 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.
> 
> 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.
> 
> Windows XP is using IRQ3 (as reported by HWiNFO32 and in the Device
> Manager), which is neither of the two vectors returned by _PRT.
> As HWiNFO32 decoded contents of the SPD EEPROMs, the i2c-i801 device is
> working under Windows. It appears that Windows has reconfigured the
> chipset independently to use another interrupt vector for the device.
> This is possible, according to the chipset datasheet [1], page 436 for
> example (PIRQ[n]_ROUT—PIRQ[A,B,C,D] Routing Control Register).
> 
> [1] https://www.intel.com/content/dam/doc/datasheet/io-controller-hub-9-datasheet.pdf
> 
> Signed-off-by: Mateusz Jończyk <mat.jonczyk@...pl>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Jean Delvare <jdelvare@...e.de>
> Previously-reviewed-by: Jean Delvare <jdelvare@...e.de>
> Previously-tested-by: Jean Delvare <jdelvare@...e.de>

I'm still happy with this patch, so you can change that back to:

Reviewed-by: Jean Delvare <jdelvare@...e.de>
Tested-by: Jean Delvare <jdelvare@...e.de>

Thanks,
-- 
Jean Delvare
SUSE L3 Support