Re: [PATCH 0/5] ARM: rskrza1: Add RZ/A1 IRQC and input switches

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Chris,

On Mon, Apr 29, 2019 at 2:21 PM Chris Brandt <Chris.Brandt@renesas.com> wrote:
> I've been hacking this support into the standard GIC driver in our BSPs
> for years now. :o

Yeah, and having that patch in your tree breaks all other GICs, as
I found out the hard way ;-)

> On Mon, Apr 29, 2019, Geert Uytterhoeven wrote:
> > I expect this driver to be reusable for RZ/A2, after adding a match
> > entry with .gic_spi_base = 4.
>
> Yes, the same IP block is in RZ/A2.
>
> So with that said, should we call this driver irq-renesas-rza1.c or just
> irq-renesas-rza.c?
> It doesn't really matter to me.
> For an RZ/A3, we might just use the same IP again.

I've learned to be reluctant to put too many wildcards in names, as it may
start to bite in the future. For driver names, it's not that bad (they can
be changed), but for DT, it's a no-go.

So for RZ/A2, I think it's best to use

    compatible = "renesas,r7s9210-irqc", "renesas,rza1-irqc";
    renesas,gic-spi-base = <4>;

(adding "renesas,gic-spi-base = <0>" to r7s72100.dtsi as I speak).

> Side note, I've seen this interrupt pin HW in some older SH4A devices
> (like SH7724 and SH7757). So it's been around for a while.

Right:

    arch/sh/kernel/cpu/sh4a/setup-sh7343.c: { 0xa4140024, 0, 8, /* INTREQ00 */
    arch/sh/kernel/cpu/sh4a/setup-sh7366.c: { 0xa4140024, 0, 8, /* INTREQ00 */
    arch/sh/kernel/cpu/sh4a/setup-sh7722.c: { 0xa4140024, 0, 8, /* INTREQ00 */
    arch/sh/kernel/cpu/sh4a/setup-sh7723.c: { 0xa4140024, 0, 8, /* INTREQ00 */
    arch/sh/kernel/cpu/sh4a/setup-sh7724.c: { 0xa4140024, 0, 8, /* INTREQ00 */

However, according to the sh7724 documentation, the register set is
slightly different, as is its sense configuration (no support for both
edges, but support for high-level interrupts).

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds