Re: [Xen-devel] [PATCH for-4.5 7/8] xen/irq: Handle multiple action per IRQ

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 18 Mar 2014, Julien Grall wrote:
> Hi Ian,
> 
> On 03/18/2014 09:33 AM, Ian Campbell wrote:
> > On Mon, 2014-03-17 at 21:05 +0000, Julien Grall wrote:
> >> For instance for the SMMU on midway, the device tree bindings is:
> >>
> >>                smmu_sata: smmu@9,20180000 {
> >>                        compatible = "arm,mmu-400";
> >>                        reg = <0x9 0x20180000 0x10000>;
> >>                        mmu-masters = <&sata 0 1 2 3 4 5 6 7 8 9>;
> >>                        #global-interrupts = <1>;
> >>                        interrupts = <0 114 4 0 114 4>;
> >>                        calxeda,smmu-secure-config-access;
> >>                        arm,smmu-isolate-devices;
> >>               };
> >>
> >> As you can see the same interrupts is used twice:
> > 
> > Is that actually valid in device tree? Or is this a quirk of the midway
> > DT?
> 
> Yes it's valid. The interrupts property for the SMMU is described as:
> 
> "Interrupt list, with the first #global-irqs entries corresponding to
> the global interrupts and any following entries corresponding to context
> interrupts, specified in order of their indexing by the SMMU.
> 
> For SMMUv2 implementations, there must be exactly one interrupt per
> context bank. In the case of a single, combined interrupt, it must be
> listed multiple times."
> 
> On midway there is only one IRQ with is used for both context interrupt
> and global interrupt. As it's the only platform on Linux with SMMU
> support in the device tree, we don't know if every platform will have
> the same behavior.

I understand that the SMMU might reuse the same IRQ for multiple
purposes. I would still handle the scenario entirely within the SMMU
driver. Can't we register a single handler for each of the IRQ listed
under the SMMU node and then figure out what was the notification for in
the handler? 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel