[v4,3/4] dt-bindings: riscv: add new riscv,isa strings for emulators

Commit Message

Conor Dooley Aug. 23, 2022, 6:33 p.m. UTC

From: Conor Dooley <[e-mail]>

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:
- ima are required
- 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
- convention says that 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
- as the above is just convention, don't apply any charset restrictions
  to reduce future churn
- 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

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 <[e-mail]>
Link: https://lore.kernel.org/linux-riscv/[e-mail]/
Reviewed-by: Andrew Jones <[e-mail]>
Acked-by: Guo Ren <[e-mail]>
Signed-off-by: Conor Dooley <[e-mail]>
---
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(-)

Comments

Heiko Stübner Aug. 24, 2022, 5:41 p.m. UTC | #1

Am Dienstag, 23. August 2022, 20:33:19 CEST schrieb Conor Dooley:
> From: Conor Dooley <[e-mail]>
> 
> 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:
> - ima are required
> - 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
> - convention says that 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
> - as the above is just convention, don't apply any charset restrictions
>   to reduce future churn
> - 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
> 
> 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

That description sounds about right, though me and regexes never
became friends, so the following will have to do:

Acked-by: Heiko Stuebner <[e-mail]>


> 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 <[e-mail]>
> Link: https://lore.kernel.org/linux-riscv/[e-mail]/
> Reviewed-by: Andrew Jones <[e-mail]>
> Acked-by: Guo Ren <[e-mail]>
> Signed-off-by: Conor Dooley <[e-mail]>
> ---
> 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..90a7cabf58fe 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 <[e-mail]>
>    - Palmer Dabbelt <[e-mail]>
> +  - Conor Dooley <[e-mail]>
>  
>  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.
>      $ref: "/schemas/types.yaml#/definitions/string"
> -    enum:
> -      - rv64imac
> -      - rv64imafdc
> +    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:_[hsxz](?:[a-z])+)*$
>  
>    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>    timebase-frequency: false
>

Rob Herring (Arm) Aug. 30, 2022, 6:03 p.m. UTC | #2

On Tue, 23 Aug 2022 19:33:19 +0100, Conor Dooley wrote:
> From: Conor Dooley <[e-mail]>
> 
> 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:
> - ima are required
> - 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
> - convention says that 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
> - as the above is just convention, don't apply any charset restrictions
>   to reduce future churn
> - 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
> 
> 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 <[e-mail]>
> Link: https://lore.kernel.org/linux-riscv/[e-mail]/
> Reviewed-by: Andrew Jones <[e-mail]>
> Acked-by: Guo Ren <[e-mail]>
> Signed-off-by: Conor Dooley <[e-mail]>
> ---
> 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(-)
> 

Reviewed-by: Rob Herring <[e-mail]>

Patch

diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
index 873dd12f6e89..90a7cabf58fe 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 <[e-mail]>
   - Palmer Dabbelt <[e-mail]>
+  - Conor Dooley <[e-mail]>
 
 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.
     $ref: "/schemas/types.yaml#/definitions/string"
-    enum:
-      - rv64imac
-      - rv64imafdc
+    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:_[hsxz](?:[a-z])+)*$
 
   # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
   timebase-frequency: false