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

Conor.Dooley
2022-02-21T07:56:02Z

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@microchip.com wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
>
> Add device tree bindings for the Microchip fpga fabric based "core" PWM
> controller.
>
> Reviewed-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.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@microchip.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@41000000 {
> + compatible = "microchip,corepwm-rtl-v4";
> + microchip,sync-update-mask = /bits/ 32 <0>;
> + clocks = <&clkcfg 30>;
> + reg = <0x41000000 0xF0>;
> + #pwm-cells = <2>;
> + };