On Tue, May 18, 2021 at 01:27:02AM +0200, Thomas Gleixner wrote: > On Mon, May 17 2021 at 21:25, Maximilian Luz wrote: > > On 5/17/21 8:40 PM, Thomas Gleixner wrote: > >> 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. > > Ok. > > > 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. > > Ok. > > > That check is essentially ignored if nr_legacy_irqs() returns a high > > enough value. > > Close enough. > > > I guess that might also be a firmware bug here? Not sure where the > > expected values come from. > > They come from the interrupt override ACPI table and if not supplied > then irq 0-15 is preset with default values, which are type=edge and > polarity=high, i.e. the opposite of what the failing driver wants. > > The ACPI table lacks an override entry for IRQ7. I looked at one of the > dmesg files in that github thread and that has overrides: > > [ 0.111674] ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl) > [ 0.111681] ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 low level) > [ 0.111688] ACPI: IRQ0 used by override. > [ 0.111692] ACPI: IRQ9 used by override. > > IRQ7 should have a corresponding entry as IRQ9 has: > > https://github.com/linux-surface/acpidumps/blob/4da0148744164cea0c924dab92f45842fde03177/surface_laptop_4_amd/apic.dsl#L178 > > Subtable Type : 02 [Interrupt Source Override] > Length : 0A > Bus : 00 > Source : 07 > Interrupt : 00000007 > Flags (decoded below) : 000F > Polarity : 3 > Trigger Mode : 3 > > > 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. > > Impressive detective work! > > Sachi, can you please try the hack below to confirm the above? > > It's not meant to be a solution, but it's the most trivial way to > validate this. > > I'm pretty sure that Windows on Surface does not care about the PIC at > all. Whether that's on purpose to safe power or just because Windows > ignores the PIC completely by now does not matter at all. No idea how > that repeated poking on the PIC makes it come alive either and TBH, I > don't care too much about it simply because Linux is able to cope with a > missing PIC as long as the ACPI tables are correct. > > I'm way too tired to think about a proper solution for that problem and > I noticed another related issue in that dmesg output: > > [ 0.272448] Failed to register legacy timer interrupt > > It's not a problem which causes failures, but it's related to the > missing PIC. But ACPI has a pretty nice means about missing legacy hardware, it's called Hardware Reduced mode. It excludes automatically the (legacy) PIC, PIT, etc. OTOH it excludes ACPI power chip as well. I haven't looked into this, just share my thoughts what else can be checked. (On Intel the MID devices use that approach) > Needs some more thoughts with brain awake... -- With Best Regards, Andy Shevchenko
