lkml.org 
[lkml]   [2022]   [Aug]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 3/4] dt-bindings: riscv: add new riscv,isa strings for emulators
On Thu, Aug 18, 2022 at 07:40:14AM +0200, Andrew Jones wrote:
> On Wed, Aug 17, 2022 at 09:12:12PM +0100, Conor Dooley wrote:
> > From: Conor Dooley <conor.dooley@microchip.com>
> >
> > The QEMU virt and spike machines currently export a riscv,isa string of
> > "rv64imafdcsuh",
> >
> > While the RISC-V foundation has been ratifying a bunch of extenstions
> > etc, the kernel has remained relatively static with what hardware is
> > supported - but the same is not true of QEMU. Using the virt machine
> > and running dt-validate on the dumped dtb fails, partly due to the
> > unexpected isa string.
> >
> > Rather than enumerate the many many possbilities, change the pattern
> > to a regex, with the following assumptions:
> > - the single letter order is fixed & we don't care about things that
> > can't even do "ima"
> > - the standard multi letter extensions are all in a "_z<foo>" format
> > where the first letter of <foo> is a valid single letter extension
> > - _s & _h are used for supervisor and hyper visor extensions.
> > - after the first two chars, a standard multi letter extension name
> > could be an english word (ifencei anyone?) so it's not worth
> > restricting the charset
> > - vendor ISA extensions begind with _x and have no charset restrictions
> > - we don't care about an e extension from an OS pov
> > - that attempting to validate the contents of the multiletter extensions
> > with dt-validate beyond the formatting is a futile, massively verbose
> > or unwieldy exercise at best.
> > - ima are required
> >
> > The following limitations also apply:
> > - multi letter extension ordering is not enforced. dt-schema does not
> > appear to allow for named match groups, so the resulting regex would
> > be even more of a headache.
> > - ditto for the numbered extensions.
> >
> > Finally, add me as a maintainer of the binding so that when it breaks
> > in the future, I can be held responsible!
> >
> > Reported-by: Rob Herring <robh@kernel.org>
> > Link: https://lore.kernel.org/linux-riscv/20220803170552.GA2250266-robh@kernel.org/
> > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > ---
> > Palmer, feel free to drop the maintainer addition. I just mostly want
> > to clean up my own mess on this when they decide to ratify more
> > extensions & this comes back up again.
> > ---
> > Documentation/devicetree/bindings/riscv/cpus.yaml | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > index 873dd12f6e89..c0e0bc5dce04 100644
> > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > @@ -9,6 +9,7 @@ title: RISC-V bindings for 'cpus' DT nodes
> > maintainers:
> > - Paul Walmsley <paul.walmsley@sifive.com>
> > - Palmer Dabbelt <palmer@sifive.com>
> > + - Conor Dooley <conor@kernel.org>
> >
> > description: |
> > This document uses some terminology common to the RISC-V community
> > @@ -79,9 +80,7 @@ properties:
> > insensitive, letters in the riscv,isa string must be all
> > lowercase to simplify parsing.
> > $ref: "/schemas/types.yaml#/definitions/string"
> > - enum:
> > - - rv64imac
> > - - rv64imafdc
> > + pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:(?:_[zsh][imafdqcbvksh]|_x)(?:[a-z])+)*$

Actually we don't want S and H extensions to be treated like Z, but rather
like X. Only Z extensions have the category character convention. (And I'm
still tempted to just drop the enforcement from Z too, since it adds
additional maintenance and we've already settled for something less than
complete.)

Thanks,
drew

> >
> > # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
> > timebase-frequency: false
> > --
> > 2.37.1
> >
>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

\
 
 \ /
  Last update: 2022-08-18 07:49    [W:0.096 / U:0.444 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site