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

Mateusz Jończyk
2024-02-16T20:20:19Z

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@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.
> The usual comment style in this file is:
>
> /*
> * We use ...
> */
>
>>> + */
>>> + }
>>> + }
>>> +
>>> 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?
> No concerns from me.
>
> I guess this only adds a message, right? It doesn't actually fix
> anything or change any behavior?
Exactly.
> This talks about "duplicate" entries, which suggests to me that they
> are identical, but I don't think they are. It sounds like it's two
> "matching" entries, i.e., two entries for the same (device, pin)?

Right.

> 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().

> Bjorn

Greetings,

Mateusz