Re: [RFC PATCH v2 25/30] include/dt-bindings: Add sh_intc IRQ - EVT conversion helper

Hi Krzysztof,

On Wed, Sep 20, 2023 at 1:51 PM Krzysztof Kozlowski <[email protected]> wrote:
> On 19/09/2023 15:02, Geert Uytterhoeven wrote:
> > On Wed, Sep 13, 2023 at 12:50 PM Krzysztof Kozlowski <[email protected]> wrote:
> >> On 13/09/2023 11:23, Yoshinori Sato wrote:
> >>> --- /dev/null
> >>> +++ b/include/dt-bindings/interrupt-controller/sh_intc.h
> >>> @@ -0,0 +1,7 @@
> >>> +/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>> + *
> >>> + * SH3/4 INTC EVT - IRQ conversion
> >>> + */
> >>> +
> >>> +#define evt2irq(evt)         ((evt) >> 5)
> >>> +#define irq2evt(irq)         ((irq) << 5)
> >>
> >> No, that's not a binding. Drop entire file.
> >
> > The issue is that the hardware documentation does not list interrupt
> > numbers, but event codes.  The latter is a sparse address space.
> > As the "interrupts" property needs interrupt numbers, we have two
> > options:
> >   1. Use hardcoded event codes and evt2irq() in DTS files.
> >      This is the approach Sato-san took,
> >   2. Use hardcoded interrupt numbers in DTS files.
> >      This would avoids the need for the evt2irq() macro in the DT bindings,
> >      but would make life slightly harder for the DTS writer and
> >      for the casual reader, as the conversion needs to be done in
> >      one's head.
> >
> > Note that the documentation for later SoCs that contain both a SuperH
> > and an ARM CPU core, usually lists both the event code and the interrupt
> > number, although the latter may be offset by 32 due to the SPI
> > interrupt base.
> >
> > I agree we do not need irq2evt() in DTS, though.
>
> Is the macro used by the drivers? I have a feeling that not, so it would
> not be suitable for the bindings, but rather as a header included in the
> DTS.

You mean irq2evt()? No, the new DT-aware drivers avoid the conversion
from IRQ numbers to events codes by storing evt2irq() values in the
interrupt table (see drivers/irqchip/irq-renesas-sh7751.c:iprmaps[]).

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

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