linux-kernel - Re: [PATCH v2 06/16] dt-bindings: timer: add Canaan k210 to Synopsys DesignWare timer

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Date:   Tue, 28 Jun 2022 00:13:14 +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 v2 06/16] dt-bindings: timer: add Canaan k210 to Synopsys
 DesignWare timer

On Mon, Jun 27, 2022 at 08:39:54PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@...rochip.com>
> 
> The Canaan k210 apparently has a Sysnopsys Designware timer but
> according to the documentation & devicetree it has 2 interrupts rather
> than the standard one. Add a custom compatible that supports the 2
> interrupt configuration and falls back to the standard binding (which
> is currently the one in use in the devicetree entry).
> 

> Link: https://canaan-creative.com/wp-content/uploads/2020/03/kendryte_standalone_programming_guide_20190311144158_en.pdf #Page 58

Firstly, it's page 51 in the framework of the document pages
enumeration.

Judging by the comment in the document above and what the HW reference
manual says regarding the IRQ signals, what you really have on K210 is
the DW APB Timer IP-cores each configured with two embedded timers.
It's done by the IP-core synthesize parameter NUM_TIMERS={1..8}, which
in your case equals to 2. A similar situation is on our SoC and, for
instance, here:

arch/arm/boot/dts/berlin2q.dtsi
arch/arm/boot/dts/berlin2.dtsi
arch/arm/boot/dts/berlin2cd.dtsi
(Though the Berlin2 APB Timer have been configured with 8 timers.)

So the correct modification would be:
1. Split up the nodes into two ones with one IRQ per each node.
2. Make sure I was right by testing the new dts out.
3. Update the DT-node only and leave the DT-bindings as is.

-Sergey

> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
> ---
>  .../bindings/timer/snps,dw-apb-timer.yaml     | 28 +++++++++++++++----
>  1 file changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/timer/snps,dw-apb-timer.yaml b/Documentation/devicetree/bindings/timer/snps,dw-apb-timer.yaml
> index d33c9205a909..9a76acc7a66f 100644
> --- a/Documentation/devicetree/bindings/timer/snps,dw-apb-timer.yaml
> +++ b/Documentation/devicetree/bindings/timer/snps,dw-apb-timer.yaml
> @@ -12,6 +12,9 @@ maintainers:
>  properties:
>    compatible:
>      oneOf:
> +      - items:
> +          - const: canaan,k210-apb-timer
> +          - const: snps,dw-apb-timer
>        - const: snps,dw-apb-timer
>        - enum:
>            - snps,dw-apb-timer-sp
> @@ -21,9 +24,6 @@ properties:
>    reg:
>      maxItems: 1
>  
> -  interrupts:
> -    maxItems: 1
> -
>    resets:
>      maxItems: 1
>  
> @@ -41,7 +41,23 @@ properties:
>  
>    clock-frequency: true
>  
> -additionalProperties: false
> +unevaluatedProperties: false
> +
> +if:
> +  properties:
> +    compatible:
> +      contains:
> +        const: canaan,k210-apb-timer
> +
> +then:
> +  properties:
> +    interrupts:
> +      maxItems: 2
> +
> +else:
> +  properties:
> +    interrupts:
> +      maxItems: 1
>  
>  required:
>    - compatible
> @@ -60,8 +76,8 @@ oneOf:
>  examples:
>    - |
>      timer@...00000 {
> -      compatible = "snps,dw-apb-timer";
> -      interrupts = <0 170 4>;
> +      compatible = "canaan,k210-apb-timer", "snps,dw-apb-timer";
> +      interrupts = <0 170 4>, <0 170 4>;
>        reg = <0xffe00000 0x1000>;
>        clocks = <&timer_clk>, <&timer_pclk>;
>        clock-names = "timer", "pclk";
> -- 
> 2.36.1
>