linux-kernel - Re: [PATCH v7 05/11] dt-bindings: pwm: add microchip corepwm binding

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Message-ID: <4c470378-7aa0-deb8-e7b5-2aa4a86cac8e@microchip.com>
Date:   Mon, 21 Feb 2022 07:55:47 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <u.kleine-koenig@...gutronix.de>
CC:     <Lewis.Hanly@...rochip.com>, <Daire.McNamara@...rochip.com>,
        <Ivan.Griffin@...rochip.com>, <atishp@...osinc.com>,
        <robh@...nel.org>, <palmer@...osinc.com>,
        <linus.walleij@...aro.org>, <brgl@...ev.pl>, <robh+dt@...nel.org>,
        <jassisinghbrar@...il.com>, <thierry.reding@...il.com>,
        <lee.jones@...aro.org>, <a.zummo@...ertech.it>,
        <alexandre.belloni@...tlin.com>, <paul.walmsley@...ive.com>,
        <palmer@...belt.com>, <aou@...s.berkeley.edu>,
        <geert@...ux-m68k.org>, <krzysztof.kozlowski@...onical.com>,
        <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pwm@...r.kernel.org>,
        <linux-rtc@...r.kernel.org>, <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v7 05/11] dt-bindings: pwm: add microchip corepwm binding

Hey Uwe,
Could you take a look at this version & see if the descriptions are 
easier to understand?
Thanks,
Conor

On 14/02/2022 13:58, conor.dooley@...rochip.com wrote:
> From: Conor Dooley <conor.dooley@...rochip.com>
> 
> Add device tree bindings for the Microchip fpga fabric based "core" PWM
> controller.
> 
> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
> Acked-by: Palmer Dabbelt <palmer@...osinc.com>
> ---
>   .../bindings/pwm/microchip,corepwm.yaml       | 81 +++++++++++++++++++
>   1 file changed, 81 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml
> 
> diff --git a/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml b/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml
> new file mode 100644
> index 000000000000..a7fae1772a81
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml
> @@ -0,0 +1,81 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pwm/microchip,corepwm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip IP corePWM controller bindings
> +
> +maintainers:
> +  - Conor Dooley <conor.dooley@...rochip.com>
> +
> +description: |
> +  corePWM is an 16 channel pulse width modulator FPGA IP
> +
> +  https://www.microsemi.com/existing-parts/parts/152118
> +
> +allOf:
> +  - $ref: pwm.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: microchip,corepwm-rtl-v4
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  "#pwm-cells":
> +    const: 2
> +
> +  microchip,sync-update-mask:
> +    description: |
> +      Depending on how the IP is instantiated, there are two modes of operation.
> +      In synchronous mode, all channels are updated at the beginning of the PWM period,
> +      and in asynchronous mode updates happen as the control registers are written.
> +      A 16 bit wide "SHADOW_REG_EN" parameter of the IP core controls whether synchronous
> +      mode is possible for each channel, and is set by the bitstream programmed to the
> +      FPGA. If the IP core is instantiated with SHADOW_REG_ENx=1, both registers that
> +      control the duty cycle for channel x have a second "shadow"/buffer reg synthesised.
> +      At runtime a bit wide register exposed to APB can be used to toggle on/off
> +      synchronised mode for all channels it has been synthesised for.
> +      Each bit of "microchip,sync-update-mask" corresponds to a PWM channel & represents
> +      whether synchronous mode is possible for the PWM channel.
> +
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 0
> +
> +  microchip,dac-mode-mask:
> +    description: |
> +      Optional, per-channel Low Ripple DAC mode is possible on this IP core. It creates
> +      a minimum period pulse train whose High/Low average is that of the chosen duty
> +      cycle. This "DAC" will have far better bandwidth and ripple performance than the
> +      standard PWM algorithm can achieve. A 16 bit DAC_MODE module parameter of the IP
> +      core, set at instantiation and by the bitstream programmed to the FPGA, determines
> +      whether a given channel operates in regular PWM or DAC mode.
> +      Each bit corresponds to a PWM channel & represents whether DAC mode is enabled
> +      for that channel.
> +
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 0
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    pwm@...00000 {
> +      compatible = "microchip,corepwm-rtl-v4";
> +      microchip,sync-update-mask = /bits/ 32 <0>;
> +      clocks = <&clkcfg 30>;
> +      reg = <0x41000000 0xF0>;
> +      #pwm-cells = <2>;
> +    };