On Thu, Feb 03, 2022 at 06:12:10PM +0100, Pierre Gondois wrote: > On 2/3/22 5:32 PM, Bjorn Helgaas wrote: > > On Thu, Feb 03, 2022 at 10:10:19AM +0100, Pierre Gondois wrote: > > > On 2/2/22 6:42 PM, Bjorn Helgaas wrote: > > > > On Wed, Feb 02, 2022 at 10:20:44AM +0000, bugzilla-daemon@xxxxxxxxxx wrote: > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=215560 > > > > > > > > > > The PCI legacy interrupts can be described with link devices, cf ACPI 6.4, > > > > > s6.2.13 "_PRT (PCI Routing Table)". > > > > > Link devices can have optional _SRS/_PRS methods to set the interrupt. > > > > > ... > > > > > > > However, _PRS/_SRS methods are checked in drivers/acpi/pci_link.c, and the > > > > > driver aborts if they are absent. > > > > > E.g.: When _PRS is missing: > > > > > ACPI: \_SB_.PCI0.LNKA: _CRS 36 not found in _PRS > > > > > ACPI: \_SB_.PCI0.LNKA: No IRQ available. Try pci=noacpi or acpi=off > > > > > > > > I assume this bug report is because something isn't working. Can > > > > you update the bugzilla with a note about what specifically isn't > > > > working and also attach a complete dmesg log and acpidump? > > > > > > The question arose while writing link devices code, so there is no > > > platform with missing _PRS/_SRS methods that I know. > > > > > > The question was more about spec compliance and the necessity to > > > have these methods when legacy interrupts are not configurable. The > > > message above (_CRS XXX not found in _PRS) can be generated for a > > > Juno for instance, and the ACPI tables are at: > > > https://github.com/tianocore/edk2-platforms/blob/master/Platform/ARM/JunoPkg/AcpiTables/AcpiSsdtRootPci.asl > > > The ACPI table need to be modified (remove _PRS and set _CRS > > > correctly). > > > > > > If the conclusion is that _PRS/_SRS are mandatory, even for > > > hard-wired interrupts, then the bugzilla can be closed. > > > > OK, so if I understand correctly, you're using Interrupt Link devices > > not because it's possible to connect a PCI interrupt to one of several > > inputs on the interrupt controller, but because the PCI default of > > "level triggered, active low" is not compatible with GICv2. > > > > The Interrupt Link device gives you a chance to specify "level > > triggered, active *high*". If you used a Source of 0 (where there > > is no Interrupt Link), there would be no way to specify that. > > > > Since this use of Interrupt Links only conveys triggering information > > and nothing is configurable, I think the OS should get that info from > > _CRS, and _PRS and _SRS should not be required. > > > > Alex made a change [1] along that line a while ago, but maybe there's > > more we should do. > > > > Bjorn > > > > [1] https://git.kernel.org/linus/92d1b381f677 > > Yes, this is exactly the situation. > > The interrupt advertised in _CRS is checked to be in _PRS at: > https://github.com/torvalds/linux/blob/26291c54e111ff6ba87a164d85d4a4e134b7315c/drivers/acpi/pci_link.c#L549 > and the _SRS method is also evaluated. > > I can submit a patch if necessary, That would be awesome. Thanks for pushing on this! Bjorn
