Re: [PATCH 5/5] dt-bindings: timer: Add CLINT bindings

[Palmer Dabbelt]

On Thu, 21 May 2020 23:29:36 PDT (-0700), seanga2@xxxxxxxxx wrote:
> On 5/22/20 1:54 AM, Anup Patel wrote:
> > On Fri, May 22, 2020 at 1:35 AM Sean Anderson <seanga2@xxxxxxxxx> wrote:
> > > On 5/21/20 9:45 AM, Anup Patel wrote:
> > > > +Required properties:
> > > > +- compatible : "sifive,clint-1.0.0" and a string identifying the actual
> > > > +  detailed implementation in case that specific bugs need to be worked around.
> > >
> > > Should the "riscv,clint0" compatible string be documented here? This
> >
> > Yes, I forgot to add this compatible string. I will add in v2.
> >
> > > peripheral is not really specific to sifive, as it is present in most
> > > rocket-chip cores.
> >
> > I agree that CLINT is present in a lot of non-SiFive RISC-V SOCs and
> > FPGAs but this IP is only documented as part of SiFive FU540 SOC.
> > (Refer, https://static.dev.sifive.com/FU540-C000-v1.0.pdf)
> >
> > The RISC-V foundation should host the CLINT spec independently
> > under https://github.com/riscv and make CLINT spec totally open.
> >
> > For now, I have documented it just like PLIC DT bindings found at:
> > Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.txt
>
> The PLIC seems to have its own RISC-V-sponsored documentation [1] which
> was split off from the older privileged specs. By your logic above,
> should it be renamed to riscv,plic0.txt (with a corresponding change in
> the documented compatible strings)?
>
> [1] https://github.com/riscv/riscv-plic-spec

Let's propose tagging that PLIC spec as v1.0.0 in the platform spec group, but
I don't see a reason why that wouldn't be viable.  Assuming that's all OK, we
can start calling this a RISC-V PLIC (in addition to a SiFive PLIC, as they'll
be compatible).

> > If RISC-V maintainers agree then I will document it as "RISC-V CLINT".
> >
> > @Palmer ?? @Paul ??

The CLINT is a SiFive spec.  It has open source RTL so it's been implemented in
other designs, but it's not a RISC-V spec.  The CLIC, which is a superset of
the CLINT, is a RISC-V spec.  IIRC it's not finished yet (it's the fast
interrupts task group), but presumably we should have a "riscv,clic-2.0.0" (or
whatever it ends up being called) compat string to go along with the
specification.

> > Regards,
> > Anup
>
> --Sean