linux-kernel - Re: [PATCH v6 1/3] dt-bindings: pwm: Add Xilinx AXI Timer

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Message-ID: <YS6M9jmTmy4EvB4k@robh.at.kernel.org>
Date:   Tue, 31 Aug 2021 15:11:34 -0500
From:   Rob Herring <robh@...nel.org>
To:     Sean Anderson <sean.anderson@...o.com>
Cc:     linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Alvaro Gamez <alvaro.gamez@...ent.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        linux-arm-kernel@...ts.infradead.org,
        Lee Jones <lee.jones@...aro.org>, michal.simek@...inx.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/3] dt-bindings: pwm: Add Xilinx AXI Timer

On Thu, Aug 26, 2021 at 05:18:28PM -0400, Sean Anderson wrote:
> This adds a binding for the Xilinx LogiCORE IP AXI Timer. This device is a
> "soft" block, so it has some parameters which would not be configurable in
> most hardware. This binding is usually automatically generated by Xilinx's
> tools, so the names and values of some properties should be kept as they
> are, if possible. In addition, this binding is already in the kernel at
> arch/microblaze/boot/dts/system.dts, and in user software such as QEMU.
> 
> The existing driver uses the clock-frequency property, or alternatively the
> /cpus/timebase-frequency property as its frequency input. Because these
> properties are deprecated, they have not been included with this schema.
> All new bindings should use the clocks/clock-names properties to specify
> the parent clock.
> 
> Because we need to init timer devices so early in boot, we determine if we
> should use the PWM driver or the clocksource/clockevent driver by the
> presence/absence, respectively, of #pwm-cells. Because both counters are
> used by the PWM, there is no need for a separate property specifying which
> counters are to be used for the PWM.
> 
> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
> ---
> 
> Changes in v6:
> - Fix incorrect schema id
> - Enumerate possible counter widths
> 
> Changes in v5:
> - Update commit message to reflect revisions
> - Fix indentation lint
> - Add example for timer binding
> - Remove xlnx,axi-timer-2.0 compatible string
> - Move schema into the timer directory
> 
> Changes in v4:
> - Remove references to generate polarity so this can get merged
> - Predicate PWM driver on the presence of #pwm-cells
> - Make some properties optional for clocksource drivers
> 
> Changes in v3:
> - Mark all boolean-as-int properties as deprecated
> - Add xlnx,pwm and xlnx,gen?-active-low properties.
> - Make newer replacement properties mutually-exclusive with what they
>   replace
> - Add an example with non-deprecated properties only.
> 
> Changes in v2:
> - Use 32-bit addresses for example binding
> 
>  .../bindings/timer/xlnx,xps-timer.yaml        | 90 +++++++++++++++++++
>  1 file changed, 90 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/xlnx,xps-timer.yaml
> 
> diff --git a/Documentation/devicetree/bindings/timer/xlnx,xps-timer.yaml b/Documentation/devicetree/bindings/timer/xlnx,xps-timer.yaml
> new file mode 100644
> index 000000000000..5be353a642aa
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/xlnx,xps-timer.yaml
> @@ -0,0 +1,90 @@
> +# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/timer/xlnx,xps-timer.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xilinx LogiCORE IP AXI Timer Device Tree Binding
> +
> +maintainers:
> +  - Sean Anderson <sean.anderson@...o.com>
> +
> +properties:
> +  compatible:
> +    contains:
> +      const: xlnx,xps-timer-1.00.a
> +
> +  clocks:
> +    maxItems: 1
> +
> +  clock-names:
> +    const: s_axi_aclk
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  reg:
> +    maxItems: 1
> +
> +  xlnx,count-width:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [8, 16, 32]
> +    default: 32
> +    description:
> +      The width of the counter(s), in bits.
> +
> +  xlnx,one-timer-only:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [ 0, 1 ]
> +    description:
> +      Whether only one timer is present in this block.
> +
> +required:
> +  - compatible
> +  - reg
> +  - xlnx,one-timer-only
> +
> +allOf:
> +  - if:
> +      required:
> +        - '#pwm-cells'
> +    then:
> +      allOf:
> +        - required:
> +            - clocks
> +        - properties:
> +            xlnx,one-timer-only:
> +              const: 0
> +    else:
> +      required:
> +        - interrupts
> +  - if:
> +      required:
> +        - clocks
> +    then:
> +      required:
> +        - clock-names
> +
> +additionalProperties: true

This needs to be false. What else do you expect to be present?

> +
> +examples:
> +  - |
> +    timer@...e0000 {
> +        clock-names = "s_axi_aclk";
> +        clocks = <&zynqmp_clk 71>;
> +        compatible = "xlnx,xps-timer-1.00.a";
> +        reg = <0x800e0000 0x10000>;
> +        interrupts = <0 39 2>;
> +        xlnx,count-width = <16>;
> +        xlnx,one-timer-only = <0x0>;
> +    };
> +
> +    timer@...f0000 {
> +        #pwm-cells = <0>;
> +        clock-names = "s_axi_aclk";
> +        clocks = <&zynqmp_clk 71>;
> +        compatible = "xlnx,xps-timer-1.00.a";
> +        reg = <0x800e0000 0x10000>;
> +        xlnx,count-width = <32>;
> +        xlnx,one-timer-only = <0x0>;
> +    };
> -- 
> 2.25.1
> 
>