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

Rafael J. Wysocki
2024-02-16T18:26:19Z

On Tue, Dec 26, 2023 at 1:50 PM Mateusz Jończyk <mat.jonczyk@o2.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.
>
> 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@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>
>
> ---
> Hello,
>
> I'm resurrecting an older patch that was discussed back in January:
>
> https://lore.kernel.org/lkml/20230121153314.6109-1-mat.jonczyk@o2.pl/T/#u
>
> To consider: should we print a warning or an error in case of duplicate
> entries? This may not be serious enough to disturb the user with an
> error message at boot.
>
> I'm also looking into modifying the i2c-i801 driver to disable its usage
> of interrupts if one did not fire.
>
> v2: - add a newline at the end of the kernel log message,
> - replace: "if (match == NULL)" -> "if (!match)"
> - patch description tweaks.
> v3: - fix C style issues pointed by Jean Delvare,
> - switch severity from warning to error.
> v3 RESEND: retested on top of v6.2-rc4
> v4: - rebase and retest on top of v6.7-rc7
> - switch severity back to warning,
> - change pr_err() to dev_warn() and simplify the code,
> - modify patch description (describe Windows behaviour etc.)
> ---
> drivers/acpi/pci_irq.c | 25 ++++++++++++++++++++++---
> 1 file changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index ff30ceca2203..1fcf72e335b0 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -203,6 +203,8 @@ static int acpi_pci_irq_find_prt_entry(struct pci_dev *dev,
> struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> struct acpi_pci_routing_table *entry;
> acpi_handle handle = NULL;
> + struct acpi_prt_entry *match = NULL;
> + const char *match_int_source = NULL;
>
> if (dev->bus->bridge)
> handle = ACPI_HANDLE(dev->bus->bridge);
> @@ -219,13 +221,30 @@ static int acpi_pci_irq_find_prt_entry(struct pci_dev *dev,
>
> entry = buffer.pointer;
> while (entry && (entry->length > 0)) {
> - if (!acpi_pci_irq_check_entry(handle, dev, pin,
> - entry, entry_ptr))
> - break;
> + struct acpi_prt_entry *curr;
> +
> + if (!acpi_pci_irq_check_entry(handle, dev, pin, entry, &curr)) {
> + if (!match) {
> + match = curr;
> + match_int_source = entry->source;
> + } else {
> + dev_warn(&dev->dev, FW_BUG

dev_info() would be sufficient here IMV.

> + "ACPI _PRT returned duplicate IRQ routing entries for INT%c: %s[%d] and %s[%d]\n",
> + pin_name(curr->pin),
> + match_int_source, match->index,
> + entry->source, curr->index);
> + /* We use the first matching entry nonetheless,
> + * for compatibility with older kernels.
> + */
> + }
> + }
> +
> entry = (struct acpi_pci_routing_table *)
> ((unsigned long)entry + entry->length);
> }
>
> + *entry_ptr = match;
> +
> kfree(buffer.pointer);
> return 0;
> }
>
> base-commit: 861deac3b092f37b2c5e6871732f3e11486f7082
> --

Bjorn, any concerns regarding this one?