Re: [PATCH 01/10] irqchip: irq-mips-gic: export gic_send_ipi

Thomas Gleixner
2015-08-28T14:22:42Z

On Fri, 28 Aug 2015, Qais Yousef wrote:
> Thanks a lot for the detailed explanation. I wasn't looking for a quick and
> dirty solution but my view of the problem is much simpler than yours so my
> idea of a solution would look quick and dirty. I have a better appreciation of
> the problem now and a way to approach it :-)
>
> From DT point of view are we OK with this form then
>
> coprocessor {
> interrupt-source = <&intc INT_SPEC COP_HWAFFINITY>;
> interrupt-sink = <&intc INT_SPEC CPU_HWAFFINITY>;
> }
>
> and if the root controller sends normal IPI as it sends normal device
> interrupts then interrupt-sink can be a standard interrupts property (like in
> my case)
>
> coprocessor {
> interrupt-source = <&intc INT_SPEC COP_HWAFFINITY>;
> interrupts = <INT_SPEC>;
> }
>
> Does this look right to you? Is there something else that needs to be covered
> still?

I'm not an DT wizard. I leave that to the DT experts.

> One more thing I can think of now is that the coprocessor will need the raw
> irq numbers that are picked by linux so that it can use them to trigger the
> IPI. Are we ok to add a function that returns this raw irq number (as opposed
> to linux irq number) directly from DT? The way this is communicated to the
> coprocessor will be platform specific.

Why do you want that to be hacked into DT?

> > To configure your coprocessor proper, we need a translation
> > mechanism from the linux interrupt number to the magic value which
> > needs to be written into the trigger register when the coprocessor
> > wants to send an interrupt or an IPI.
> >
> > int irq_get_irq_hwcfg(unsigned int irq, struct irq_hwcfg *cfg);
> >
> > struct irq_hwcfg needs to be defined, but it might look like this:
> >
> > {
> > /* Generic fields */
> > x;
> > ...
> > union {
> > mips_gic;
> > ...
> > };
> > };

That function provides you the information which you have to hand over
to your coprocessor firmware.

Thanks,

tglx