[PATCH] dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6

[PATCH] dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6

[Geert Uytterhoeven]

On R-Car X5H, SCIF serial interfaces are wired to three DMACs, hence
referring to up to six DMA channels.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 Documentation/devicetree/bindings/serial/renesas,scif.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/serial/renesas,scif.yaml b/Documentation/devicetree/bindings/serial/renesas,scif.yaml
index 3d5f8ca744783550..a30c79cc455264e0 100644
--- a/Documentation/devicetree/bindings/serial/renesas,scif.yaml
+++ b/Documentation/devicetree/bindings/serial/renesas,scif.yaml
@@ -146,14 +146,14 @@ properties:
 
   dmas:
     minItems: 2
-    maxItems: 4
+    maxItems: 6
     description:
       Must contain a list of pairs of references to DMA specifiers, one for
       transmission, and one for reception.
 
   dma-names:
     minItems: 2
-    maxItems: 4
+    maxItems: 6
     items:
       enum:
         - tx
-- 
2.43.0

Re: [PATCH] dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] dt-bindings: schema allows 6 DMAs for older SCIF hardware
--

commit ca96f7e40234020713acb3baf706d0b07d5dcc48
Author: Geert Uytterhoeven <geert@linux-m68k.org>

dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6

This commit updates the renesas,scif device tree binding to allow up to 6
DMA channels. This supports the R-Car X5H hardware where SCIF serial
interfaces are connected to three DMACs.

> diff --git a/Documentation/devicetree/bindings/serial/renesas,scif.yaml b/Documentation/devicetree/bindings/serial/renesas,scif.yaml
> index 82f54446835e6..b465c93c8357f 100644
> --- a/Documentation/devicetree/bindings/serial/renesas,scif.yaml
> +++ b/Documentation/devicetree/bindings/serial/renesas,scif.yaml
[ ... ]
> @@ -145,14 +145,14 @@ properties:
>  
>    dmas:
>      minItems: 2
> -    maxItems: 4
> +    maxItems: 6

[Severity: Low]
Does modifying the global properties.dmas limit relax the schema too much
for older hardware variants? By changing the top-level maxItems to 6, older
SCIF generations (like Gen1-Gen4) will now pass dt_binding_check even if a
device tree incorrectly specifies more than 4 DMA channels. Should this
expanded limit be constrained to the R-Car X5H compatible string using an
if-then conditional block instead?

>      description:
>        Must contain a list of pairs of references to DMA specifiers, one for
>        transmission, and one for reception.
>  
>    dma-names:
>      minItems: 2
> -    maxItems: 4
> +    maxItems: 6

[Severity: Low]
Similarly, does changing the global properties.dma-names maxItems to 6
allow invalid configurations for older SoCs to pass validation? If previous
hardware only supports up to 4 DMA names, applying this limit globally
bypasses the stricter constraints of older generations.

>      items:
>        enum:
>          - tx

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/4d6e5ac045af387dde8ef3810ce08c7cb079fc29.1789653872.git.geert@linux-m68k.org?part=1

Re: [PATCH] dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6

[Geert Uytterhoeven]

Hi Sashiko,

On Thu, 17 Sept 2026 at 16:14, <sashiko-bot@kernel.org> wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] dt-bindings: schema allows 6 DMAs for older SCIF hardware
> --
>
> commit ca96f7e40234020713acb3baf706d0b07d5dcc48
> Author: Geert Uytterhoeven <geert@linux-m68k.org>
>
> dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6
>
> This commit updates the renesas,scif device tree binding to allow up to 6
> DMA channels. This supports the R-Car X5H hardware where SCIF serial
> interfaces are connected to three DMACs.

I wouldn't bother adding further restrictions, as these are not related
to the actual I2C block, but to on-SoC wiring.  DMARQ is just a single
signal going from the serial block to one or more DMAC instances.
The number may also differs among serial instances on an SoC.

See also my similar reply for rcar-i2c:
https://lore.kernel.org/all/CAMuHMdXj04QoxituCF3wRcyzN7qZrVBn7-ukNkKDd0OfhB8zOQ@mail.gmail.com/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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

Re: [PATCH] dt-bindings: serial: renesas,scif: Increase number of DMA channels to 6

[Wolfram Sang]

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On Thu, Sep 17, 2026 at 04:06:50PM +0200, Geert Uytterhoeven wrote:
> On R-Car X5H, SCIF serial interfaces are wired to three DMACs, hence
> referring to up to six DMA channels.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>


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