[PATCH v2] acpi,pci: warn about duplicate IRQ routing entries returned from _PRT

Mateusz Jończyk
2022-11-13T17:35:24Z

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.

Print a warning to dmesg if duplicate interrupt routing entries are
present, so that 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 was nonfunctional unless its interrupt
usage was 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.

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.com>

--
v2: - add a newline at the end of the kernel log message,
- replace: "if (match == NULL)" -> "if (!match)"
- patch description tweaks.

Tested on two computers, including the affected Dell Latitude E6500 laptop.

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 08e15774fb9f..a4e41b7b71ed 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 {
+ pr_warn(FW_BUG
+ "ACPI _PRT returned duplicate IRQ routing entries for device "
+ "%04x:%02x:%02x[INT%c]: %s[%d] and %s[%d].\n",
+ curr->id.segment, curr->id.bus, curr->id.device,
+ pin_name(curr->pin),
+ match_int_source, match->index,
+ entry->source, curr->index);
+ // we use the first matching entry nonetheless
+ }
+ }
+
entry = (struct acpi_pci_routing_table *)
((unsigned long)entry + entry->length);
}

+ *entry_ptr = match;
+
kfree(buffer.pointer);
return 0;
}

base-commit: f0c4d9fc9cc9462659728d168387191387e903cc
--
2.25.1