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From:   Rob Herring <robh+dt@kernel.org>
Date:   Tue, 10 Sep 2019 09:33:32 +0100
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Subject: Re: [RFC PATCH 1/2] dt-bindings: pwm: Convert PWM bindings to json-schema
To:     Krzysztof Kozlowski <krzk@kernel.org>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux PWM List <linux-pwm@vger.kernel.org>,
        devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Maciej Falkowski <m.falkowski@samsung.com>,
        linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        Linux LED Subsystem <linux-leds@vger.kernel.org>,
        linux-clk <linux-clk@vger.kernel.org>
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On Mon, Sep 9, 2019 at 7:35 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
>
> Convert generic PWM bindings to DT schema format using json-schema.  The
> consumer bindings are split to separate file.
>
> Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> ---
>  .../devicetree/bindings/clock/pwm-clock.txt   |  2 +-
>  .../bindings/display/bridge/ti,sn65dsi86.txt  |  2 +-
>  .../devicetree/bindings/display/ssd1307fb.txt |  2 +-
>  .../bindings/leds/backlight/pwm-backlight.txt |  2 +-
>  .../devicetree/bindings/leds/leds-pwm.txt     |  2 +-
>  .../devicetree/bindings/mfd/max77693.txt      |  2 +-
>  .../bindings/pwm/atmel-hlcdc-pwm.txt          |  2 +-
>  .../devicetree/bindings/pwm/atmel-pwm.txt     |  2 +-
>  .../devicetree/bindings/pwm/atmel-tcb-pwm.txt |  2 +-
>  .../bindings/pwm/brcm,bcm7038-pwm.txt         |  2 +-
>  .../bindings/pwm/brcm,iproc-pwm.txt           |  2 +-
>  .../devicetree/bindings/pwm/brcm,kona-pwm.txt |  2 +-
>  .../devicetree/bindings/pwm/img-pwm.txt       |  2 +-
>  .../devicetree/bindings/pwm/imx-pwm.txt       |  2 +-
>  .../devicetree/bindings/pwm/imx-tpm-pwm.txt   |  2 +-
>  .../bindings/pwm/lpc1850-sct-pwm.txt          |  2 +-
>  .../devicetree/bindings/pwm/mxs-pwm.txt       |  2 +-
>  .../bindings/pwm/nvidia,tegra20-pwm.txt       |  2 +-
>  .../bindings/pwm/nxp,pca9685-pwm.txt          |  2 +-
>  .../devicetree/bindings/pwm/pwm-bcm2835.txt   |  2 +-
>  .../devicetree/bindings/pwm/pwm-berlin.txt    |  2 +-
>  .../bindings/pwm/pwm-consumers.yaml           | 76 +++++++++++++++++++
>  .../devicetree/bindings/pwm/pwm-fsl-ftm.txt   |  2 +-
>  .../devicetree/bindings/pwm/pwm-hibvt.txt     |  2 +-
>  .../devicetree/bindings/pwm/pwm-lp3943.txt    |  2 +-
>  .../devicetree/bindings/pwm/pwm-mediatek.txt  |  2 +-
>  .../devicetree/bindings/pwm/pwm-meson.txt     |  2 +-
>  .../devicetree/bindings/pwm/pwm-mtk-disp.txt  |  2 +-
>  .../bindings/pwm/pwm-omap-dmtimer.txt         |  2 +-
>  .../devicetree/bindings/pwm/pwm-rockchip.txt  |  2 +-
>  .../devicetree/bindings/pwm/pwm-sifive.txt    |  2 +-
>  .../devicetree/bindings/pwm/pwm-stm32-lp.txt  |  2 +-
>  .../devicetree/bindings/pwm/pwm-stm32.txt     |  2 +-
>  .../devicetree/bindings/pwm/pwm-tiecap.txt    |  2 +-
>  .../devicetree/bindings/pwm/pwm-tiehrpwm.txt  |  2 +-
>  .../devicetree/bindings/pwm/pwm-zx.txt        |  2 +-
>  Documentation/devicetree/bindings/pwm/pwm.txt | 69 -----------------
>  .../devicetree/bindings/pwm/pwm.yaml          | 30 ++++++++
>  .../bindings/pwm/renesas,pwm-rcar.txt         |  2 +-
>  .../bindings/pwm/renesas,tpu-pwm.txt          |  4 +-
>  .../devicetree/bindings/pwm/spear-pwm.txt     |  2 +-
>  .../devicetree/bindings/pwm/st,stmpe-pwm.txt  |  2 +-
>  .../devicetree/bindings/pwm/ti,twl-pwm.txt    |  2 +-
>  .../devicetree/bindings/pwm/ti,twl-pwmled.txt |  2 +-
>  .../devicetree/bindings/pwm/vt8500-pwm.txt    |  2 +-
>  .../bindings/regulator/pwm-regulator.txt      |  2 +-
>  .../devicetree/bindings/timer/ingenic,tcu.txt |  2 +-

We've been leaving the .txt file with a reference to the schema file
to avoid doing all the updates. But as you've done it already, that's
good.

>  47 files changed, 151 insertions(+), 114 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/pwm/pwm-consumers.yaml
>  delete mode 100644 Documentation/devicetree/bindings/pwm/pwm.txt
>  create mode 100644 Documentation/devicetree/bindings/pwm/pwm.yaml

[...]

> diff --git a/Documentation/devicetree/bindings/pwm/pwm-consumers.yaml b/Documentation/devicetree/bindings/pwm/pwm-consumers.yaml
> new file mode 100644
> index 000000000000..39c844fe6338
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm-consumers.yaml

We already have a PWM consumer schema in dt-schema repository. It
doesn't have the descriptions because we need permission to relicense.
My aim is to have all common schema in the dt-schema repo, but we have
a mixture because of needing to relicense.

> @@ -0,0 +1,76 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pwm/pwm-consumers.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Specifying PWM information for devices
> +
> +maintainers:
> +  - Thierry Reding <thierry.reding@gmail.com>
> +
> +description: |
> +  PWM properties should be named "pwms". The exact meaning of each pwms
> +  property must be documented in the device tree binding for each device.
> +  An optional property "pwm-names" may contain a list of strings to label
> +  each of the PWM devices listed in the "pwms" property. If no "pwm-names"
> +  property is given, the name of the user node will be used as fallback.
> +
> +  Drivers for devices that use more than a single PWM device can use the
> +  "pwm-names" property to map the name of the PWM device requested by the
> +  pwm_get() call to an index into the list given by the "pwms" property.
> +
> +properties:
> +  pwms:
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    description: |
> +      Phandle to PWM controller node and pwm-specifier (controller specific).
> +      pwm-specifier typically encodes the chip-relative PWM number and the PWM
> +      period in nanoseconds.
> +      Optionally, the pwm-specifier can encode a number of flags (defined in
> +      <dt-bindings/pwm/pwm.h>) in a third cell:
> +        - PWM_POLARITY_INVERTED: invert the PWM signal polarity
> +
> +  pwm-names:
> +    $ref: /schemas/types.yaml#/definitions/string-array
> +    description:
> +      A list of strings to label each of the PWM devices listed in the "pwms"
> +      property. If no "pwm-names" property is given, the name of the user node
> +      will be used as fallback.
> +
> +required:
> +  - pwms

Doing this means every consumer has to include this file where as I do
'select: true' some every occurrence of these properties is checked.
We're generally only including other schema on the provider side.

> +
> +dependencies:
> +  pwm-names: [ pwms ]
> +
> +examples:
> +  - |
> +    // The following example could be used to describe a PWM-based
> +    // backlight device:
> +
> +    pwm: pwm {
> +      #pwm-cells = <2>;
> +    };
> +
> +    bl: backlight {
> +      pwms = <&pwm 0 5000000>;
> +      pwm-names = "backlight";
> +    };
> +
> +    // Note that in the example above, specifying the "pwm-names" is redundant
> +    // because the name "backlight" would be used as fallback anyway.
> +
> +  - |
> +    // Example with optional PWM specifier for inverse polarity
> +
> +    #include <dt-bindings/pwm/pwm.h>
> +
> +    pwm2: pwm {
> +      #pwm-cells = <3>;
> +    };
> +
> +    backlight {
> +      pwms = <&pwm2 0 5000000 PWM_POLARITY_INVERTED>;
> +      pwm-names = "backlight";
> +    };

> diff --git a/Documentation/devicetree/bindings/pwm/pwm.yaml b/Documentation/devicetree/bindings/pwm/pwm.yaml
> new file mode 100644
> index 000000000000..5d8029f11ccc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm.yaml
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pwm/pwm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: PWM controllers (providers)
> +
> +maintainers:
> +  - Thierry Reding <thierry.reding@gmail.com>
> +
> +properties:
> +  $nodename:
> +    pattern: "^pwm(@.*)?$"

Copy the pattern for spi. We allow for 'pwm-[0-9]' for cases like GPIO PWMs.

> +
> +  "#pwm-cells":
> +    $ref: /schemas/types.yaml#/definitions/uint32

You don't actually need to define the type as we already have for '#.*-cells'

> +    description:
> +      Number of cells in a PWM specifier.
> +
> +required:
> +  - "#pwm-cells"
> +
> +examples:
> +  - |
> +    pwm: pwm@7000a000 {
> +      compatible = "nvidia,tegra20-pwm";
> +      reg = <0x7000a000 0x100>;
> +      #pwm-cells = <2>;
> +    };