Re: [PATCH] dt-bindings: timer: renesas,tmu: Document input capture interrupt

Hi Conor,

On Mon, Jan 15, 2024 at 5:13 PM Conor Dooley <[email protected]> wrote:
> On Mon, Jan 15, 2024 at 02:45:39PM +0100, Geert Uytterhoeven wrote:
> > Some Timer Unit (TMU) instances with 3 channels support a fourth
> > interrupt: an input capture interrupt for the third channel.
> >
> > While at it, document the meaning of the four interrupts, and add
> > "interrupt-names" for clarity.
> >
> > Update the example to match reality.
> >
> > Inspired by a patch by Yoshinori Sato for SH.
> >
> > Signed-off-by: Geert Uytterhoeven <[email protected]>

> > --- a/Documentation/devicetree/bindings/timer/renesas,tmu.yaml
> > +++ b/Documentation/devicetree/bindings/timer/renesas,tmu.yaml
> > @@ -46,7 +46,19 @@ properties:
> >
> >    interrupts:
> >      minItems: 2
> > -    maxItems: 3
> > +    items:
> > +      - description: Underflow interrupt 0
> > +      - description: Underflow interrupt 1
> > +      - description: Underflow interrupt 2
> > +      - description: Input capture interrupt 2
>
> Seeing "input capture interrupt 2" makes me wonder, are there two (or
> more!) other input capture interrupts that are still out there,
> undocumented, and looking for a home?

SoCs can have multiple TMU instances.
Each TMU instance has 2 or 3 timer channels.
Each timer channel has an underflow interrupt.
Only the third channel may have an optional input capture interrupt
(which is not supported yet by the Linux driver).
Hence each instance can have 2, 3, or 4 interrupts.

See "RZ/G Series, 2nd Generation User's Manual: Hardware"[1],
Section 69 ("Timer Unit (TMU)":
  - Figure 69.2: Block Diagram of TMU,
  - Section 69: Interrupt

Note that the documentation uses a monotonic increasing numbering
of the channels, across all instances.

[1] https://www.renesas.com/us/en/products/microcontrollers-microprocessors/rz-mpus/rzg2h-ultra-high-performance-microprocessors-quad-core-arm-cortex-a57-and-quad-core-arm-cortex-a53-cpus-3d

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