On 5/17/21 8:40 PM, Thomas Gleixner wrote:
Max,
On Sat, May 15 2021 at 00:47, Maximilian Luz wrote:
I believe the theory was that, while the PIC is advertised in ACPI, it
might be expected to not be used and only present for some legacy reason
(therefore untested and buggy). Which I believe led to the question
whether we shouldn't prefer IOAPIC on systems like that in general. So I
guess it comes down to how you define "systems like that". By Tomas'
comment, I guess it should be possible to implement this as "systems
that should prefer IOAPIC over legacy PIC" quirk.
I guess all modern machines should have an IOAPIC, so it might also be
preferable to expand that definition, maybe over time and with enough
testing.
I just double checked and we actually can boot just fine without the
PIC even when it is advertised, but disfunctional.
Can you please add "apic=verbose" to the kernel command line and provide
full dmesg output for a kernel w/o your patch and one with your patch
applied?
I don't actually own an affected device, but I'm sure Sachi can provide
you with that.
As far as we can tell, due to the NULL PIC being chosen nr_legacy_irqs()
returns 0. That in turn causes mp_check_pin_attr() to return false
because is_level and active_low don't seem to match the expected values.
That check is essentially ignored if nr_legacy_irqs() returns a high
enough value. I guess that might also be a firmware bug here? Not sure
where the expected values come from.
Due to this, mp_map_pin_to_irq() fails with -EBUSY which causes
acpi_register_gsi() to fail. That fails in acpi_dev_get_irqresource(),
which causes the IRQ resource to be marked as disabled.
Down the line, this then causes platform_get_irq() to return -EINVAL,
because the IRQ we're trying to get has the IORESOURCE_DISABLED bit set.
Sachi can probably walk you through this a bit better as she's the one
who tracked this down. See also [1, 2] and following comments.
Regards,
Max
[1]: https://github.com/linux-surface/linux-surface/issues/425#issuecomment-835309201
[2]: https://github.com/linux-surface/linux-surface/issues/425#issuecomment-835261784
