On Fri, 26 Aug 2016 10:08:13 +0100 Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote: > [ +Sinan ] > > On Thu, Aug 25, 2016 at 07:59:17PM +0100, Marc Zyngier wrote: > > [...] > > > > Thanks, Marc! It works, I tested on current X-Gene platforms that uses > > > GICv2 and GICv2m. > > > > > > Will you commit this change? It will be a huge help as going with > > > interrupt link will require firmware change. > > > > Not for the time being. We now have an understanding of *why* things do > > not work, but Lorenzo seems to have a good grasp on what we can do to > > address it correctly, and we should explore this first. If (and only if) > > there is a consensus that firmware already does all it should, then > > I'll turn this hack into a proper series. > > For the records, it is a discussion that already took place: > > https://lkml.org/lkml/2016/3/14/923 > > As I have said there are already ARM64 systems with ACPI tables > out there using PCI interrupt links; I doubt that Qualcomm systems > allow to reconfigure the GIC interrupt pin allocated to legacy PCI > IRQs through interrupt links _SRS (hey it is *empty* :)), > therefore: > > a) Some (the above is just an example from the mailing lists I am not > picking on anyone it is just for the sake of this discussion, I have > not dumped all ARM partners _PRT from their ACPI tables to check) > ACPI tables must be rewritten because they are not FW compliant > > OR > > b) We allow PCI interrupt links to be used for static interrupt > configurations > > OR > > c) We ignore the polarity flag (only for PCI legacy IRQs ? I wonder > how GIC code can detect from which part of the kernel the interrupt > request is coming, unless we implement an ACPI-PCI-legacy-IRQ-special > gem) > > Comments ? I'm not overly keen on (c), as it is pretty hard to find out where the request is coming from (and the hack I previously posted opens the door to all kind of undetected misconfiguration). We *could* use a stacked irqchip to represent the inverter, but it feels like using a car sized hammer to squash a tiny fly. (b) seems like the right thing to do, but I cannot comment on whether or not this is compliant with the specification. Thanks, M. -- Jazz is not dead. It just smells funny. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
