Re: [PATCH 1/3] dt-bindings: interrupt-controller: Add Sophgo SG2044 ACLINT SSWI

[Conor Dooley <conor@kernel.org>]

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On Sat, Oct 05, 2024 at 08:46:37AM +0800, Inochi Amaoto wrote:
> On Fri, Oct 04, 2024 at 04:44:22PM +0100, Conor Dooley wrote:
> > On Fri, Oct 04, 2024 at 04:05:55PM +0800, Inochi Amaoto wrote:
> > > Sophgo SG2044 has a new version of T-HEAD C920, which implement
> > > a fully featured ACLINT device. This ACLINT has an extra SSWI
> > > field to support fast S-mode IPI.
> > > 
> > > Add necessary compatible string for the T-HEAD ACLINT sswi device.
> > > 
> > > Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
> > > ---
> > >  .../thead,c900-aclint-sswi.yaml               | 58 +++++++++++++++++++
> > >  1 file changed, 58 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/thead,c900-aclint-sswi.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/thead,c900-aclint-sswi.yaml b/Documentation/devicetree/bindings/interrupt-controller/thead,c900-aclint-sswi.yaml
> > > new file mode 100644
> > > index 000000000000..0106fbf3ea1f
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/interrupt-controller/thead,c900-aclint-sswi.yaml
> > > @@ -0,0 +1,58 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/interrupt-controller/thead,c900-aclint-sswi.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Sophgo sg2044 ACLINT Supervisor-level Software Interrupt Device
> > > +
> > > +maintainers:
> > > +  - Inochi Amaoto <inochiama@outlook.com>
> > > +
> > > +description:
> > > +  The SSWI device is a part of the riscv ACLINT device. It provides
> > > +  supervisor-level IPI functionality for a set of HARTs on a RISC-V
> > > +  platform. It provides a register to set an IPI (SETSSIP) for each
> > > +  HART connected to the SSWI device.
> > 
> > If it is part of the aclint, why should it have a separate node, rather
> > than be part of the existing aclint node as a third reg property?
> 
> For aclint, the current nodes that have documented are mswi and mtime.
> Since the mtime is a M-mode time source, it is not suitable to add the
> sswi reg into this device. For mswi, it is OK to add a sswi reg, but
> this will cause problem while checking "interrupt-extend". Do we just
> double the maxItem? Or just left it unchanged?
> 
> Another reason to add it as a separate node is that the draft says
> sswi can be multiple. If we add this device by adding reg. It will be
> hard if we have multiple sswi devices but one mswi device.

Ah, I see we do indeed have 2 devices already for the aclint, one for
mswi and mtimer.

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