[+cc Rafael, Alex, Marc] 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
