On Tue, 16 Dec 2014 13:56:26 +0100 (CET)
Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Tue, 16 Dec 2014, Boris Brezillon wrote:
> > Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > > Install the timer interrupt as a demultiplexing interrupt.
> >
> > I can try to hack the AIC irqchip driver to implement this demux logic,
> > but this logic can't be placed in the PIT (Periodic Interval Timer)
> > driver itself, because the shared IRQ line is used by the at91 clock
> > controller (PMC) which is providing the clock to the PIT device.
> > This gives the following dependency graph:
> >
> > PIT =depends-on=> Master Clock =provided-by=> PMC =needs=> PMC IRQ.
>
> It never can be a part of a device driver. This is a property of the
> interrupt controller which fails to provide a proper demux for this
> irq line in the first place.
>
> So you fake the demux in the irq chip driver, where you provide the
> pseudo chip and the demux logic. None of the device drivers (PIT, PMC,
> UART ...) even knows about that.
>
> |--------| |--------|
> | AIC |-------------| Pseudo |---- PIT
> | | | chip |---- PMC
> | | | |---- UART
> | | |--------|
> | |--- devX
> | |--- devY
> | |--- devZ
> |--------|
>
> So PIT, PMC and UART get interrupt numbers handed out which are
> outside of the interrupt space of AIC.
Okay, that's what I had in mind, thanks for clarifying this aspect.
Regarding the DT representation, it should look like this, right ?
aic: interrupt-controller@fffff000 {
#interrupt-cells = <3>;
compatible = "atmel,at91rm9200-aic";
interrupt-controller;
reg = <0xfffff000 0x200>;
atmel,external-irqs = <29 30 31>;
irq1_demux: irq1-demux {
#interrupt-cells = <1>;
interrupt-controller;
}
};
pit: timer@fffffd30 {
compatible = "atmel,at91sam9260-pit";
reg = <0xfffffd30 0xf>;
/* 0 is the id reserved for the PIT */
interrupts-extended = <&irq1_demux 0>;
clocks = <&mck>;
};
pmc: pmc@fffffc00 {
compatible = "atmel,at91sam9260-pmc";
reg = <0xfffffc00 0x100>;
/* 1 is the id reserved for the PMC */
interrupts-extended = <&irq1_demux 1>;
[...]
};
Regards,
Boris
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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