linux-kernel - Re: [PATCH 06/14] spi: dt-bindings: dw-apb-ssi: update spi-{r,t}x-bus-width for dwc-ssi

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Date:   Mon, 20 Jun 2022 23:56:54 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Conor Dooley <mail@...chuod.ie>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Niklas Cassel <niklas.cassel@....com>,
        Dillon Min <dillon.minfei@...il.com>,
        Heng Sia <jee.heng.sia@...el.com>,
        Jose Abreu <joabreu@...opsys.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
        alsa-devel@...a-project.org, linux-spi@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 06/14] spi: dt-bindings: dw-apb-ssi: update
 spi-{r,t}x-bus-width for dwc-ssi

On Sat, Jun 18, 2022 at 01:30:28PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@...rochip.com>
> 
> snps,dwc-ssi-1.01a has a single user - the Canaan k210, which uses a
> width of 4 for spi-{r,t}x-bus-width. Update the binding to reflect
> this.
> 
> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
> ---
>  .../bindings/spi/snps,dw-apb-ssi.yaml         | 48 ++++++++++++++-----
>  1 file changed, 35 insertions(+), 13 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> index e25d44c218f2..f2b9e3f062cd 100644
> --- a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> +++ b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> @@ -135,19 +135,41 @@ properties:
>        of the designware controller, and the upper limit is also subject to
>        controller configuration.
>  
> -patternProperties:
> -  "^.*@[0-9a-f]+$":
> -    type: object
> -    properties:
> -      reg:
> -        minimum: 0
> -        maximum: 3
> -
> -      spi-rx-bus-width:
> -        const: 1
> -
> -      spi-tx-bus-width:
> -        const: 1
> +if:
> +  properties:
> +    compatible:
> +      contains:
> +        const: snps,dwc-ssi-1.01a
> +
> +then:
> +  patternProperties:
> +    "^.*@[0-9a-f]+$":
> +      type: object
> +      properties:
> +        reg:
> +          minimum: 0
> +          maximum: 3
> +
> +        spi-rx-bus-width:
> +          const: 4
> +
> +        spi-tx-bus-width:
> +          const: 4
> +
> +else:
> +  patternProperties:
> +    "^.*@[0-9a-f]+$":
> +      type: object
> +      properties:
> +        reg:
> +          minimum: 0
> +          maximum: 3
> +
> +        spi-rx-bus-width:
> +          const: 1
> +
> +        spi-tx-bus-width:
> +          const: 1

You can just use a more relaxed constraint "enum: [1 2 4 8]" here
irrespective from the compatible string. The modern DW APB SSI
controllers of v.4.* and newer also support the enhanced SPI Modes too
(Dual, Quad and Octal). Since the IP-core version is auto-detected at
run-time there is no way to create a DT-schema correctly constraining
the Rx/Tx SPI bus widths. So let's keep the
compatible-string-independent "patternProperties" here but just extend
the set of acceptable "spi-rx-bus-width" and "spi-tx-bus-width"
properties values.

Note the DW APB SSI/AHB SSI driver currently doesn't support the
enhanced SPI modes. So I am not sure whether the multi-lines Rx/Tx SPI
bus indeed works for Canaan K210 AHB SSI controller. AFAICS from the
DW APB SSI v4.01a manual the Enhanced SPI mode needs to be properly
activated by means of the corresponding CSR. So most likely the DW AHB
SSI controllers need some specific setups too.

-Sergey

>  
>  unevaluatedProperties: false
>  
> -- 
> 2.36.1
>