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

[Rafael J. Wysocki]

On Fri, Feb 16, 2024 at 9:20 PM Mateusz Jończyk <mat.jonczyk@xxxxx> wrote:
>
> 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@xxxxx> 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@xxxxx>
> >>> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> >>> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> >>> Cc: Len Brown <lenb@xxxxxxxxxx>
> >>> Cc: Borislav Petkov <bp@xxxxxxx>
> >>> Cc: Jean Delvare <jdelvare@xxxxxxx>
> >>> Previously-reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
> >>> Previously-tested-by: Jean Delvare <jdelvare@xxxxxxx>
> >>>
> >>> ---
> >>> Hello,
> >>>
> >>> I'm resurrecting an older patch that was discussed back in January:
> >>>
> >>> https://lore.kernel.org/lkml/20230121153314.6109-1-mat.jonczyk@xxxxx/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().

I don't quite see a connection between the above and the log level.