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Date: Tue, 13 Feb 2024 22:39:08 +0100
From: Jean Delvare <jdelvare@suse.de>
To: Mateusz =?UTF-8?B?Sm/FhGN6eWs=?= <mat.jonczyk@o2.pl>
Cc: linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, Bjorn Helgaas
 <bhelgaas@google.com>, "Rafael J. Wysocki" <rafael@kernel.org>, Len Brown
 <lenb@kernel.org>, Borislav Petkov <bp@suse.de>
Subject: Re: [PATCH v4] acpi,pci: warn about duplicate IRQ routing entries
 returned from _PRT
Message-ID: <20240213223908.435aec7b@endymion.delvare>
In-Reply-To: <20231226124254.66102-1-mat.jonczyk@o2.pl>
References: <20231226124254.66102-1-mat.jonczyk@o2.pl>
Organization: SUSE Linux
Precedence: bulk
MIME-Version: 1.0
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Hi Mateusz,

On Tue, 26 Dec 2023 13:42:54 +0100, Mateusz Jo=C5=84czyk 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.
>=20
> 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.
>=20
> 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=3D0x10" module parameter).
>=20
> 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:
>=20
>         [...]
>         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)
>=20
> Existence of duplicate entries in a table returned by the _PRT method
> was confirmed by disassembling the ACPI DSDT table.
>=20
> 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=E2=80=94PIRQ[A,B,C,D] Routing Control Register).
>=20
> [1] https://www.intel.com/content/dam/doc/datasheet/io-controller-hub-9-d=
atasheet.pdf
>=20
> Signed-off-by: Mateusz Jo=C5=84czyk <mat.jonczyk@o2.pl>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Jean Delvare <jdelvare@suse.de>
> Previously-reviewed-by: Jean Delvare <jdelvare@suse.de>
> Previously-tested-by: Jean Delvare <jdelvare@suse.de>

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

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

Thanks,
--=20
Jean Delvare
SUSE L3 Support