linux-kernel - Re: [RFC PATCH 05/10] dt-bindings: pwm: Add bindings for PWM function in Netronix EC

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Date:   Sun, 21 Jun 2020 20:41:23 +0200
From:   Andreas Kemnade <andreas@...nade.info>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>
Cc:     linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
        Stephan Gerhold <stephan@...hold.net>,
        Lubomir Rintel <lkundrak@...sk>,
        Mark Brown <broonie@...nel.org>, allen <allen.chen@....com.tw>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        devicetree@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-rtc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Heiko Stuebner <heiko@...ech.de>,
        Josua Mayer <josua.mayer@....eu>
Subject: Re: [RFC PATCH 05/10] dt-bindings: pwm: Add bindings for PWM
 function in Netronix EC

On Sun, 21 Jun 2020 00:42:16 +0200
Jonathan Neuschäfer <j.neuschaefer@....net> wrote:

> The Netronix embedded controller as found in Kobo Aura and Tolino Shine
> supports one PWM channel, which is used to control the frontlight
> brightness on these devices.
> 
> Known problems:
> - `make dt_binding_check` shows the following warnings:
>   Documentation/devicetree/bindings/mfd/netronix,ntxec.example.dts:49.17-42:
>   Warning (pwms_property): /example-0/backlight:pwms: cell 2 is not a
>   phandle reference
>   Documentation/devicetree/bindings/mfd/netronix,ntxec.example.dts:49.17-42:
>   Warning (pwms_property): /example-0/backlight:pwms: Could not get
>   phandle node for (cell 2)
> 
In the tolino sources in ./drivers/misc/ntx-misc.c I find this line

        if(4==gptHWCFG->m_val.bFL_PWM) {

No idea what it does but I would expect to have a kind of translation to
a dt property?

> Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@....net>
> ---
>  .../bindings/mfd/netronix,ntxec.yaml          | 13 ++++++++
>  .../bindings/pwm/netronix,ntxec-pwm.yaml      | 33 +++++++++++++++++++
>  2 files changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> index 596df460f98eb..6562c41c5a9a9 100644
> --- a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> +++ b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> @@ -31,6 +31,9 @@ properties:
>      description:
>        The EC can signal interrupts via a GPIO line
> 
> +  pwm:
> +    $ref: ../pwm/netronix,ntxec-pwm.yaml
> +
>  required:
>    - compatible
>    - reg
> @@ -53,5 +56,15 @@ examples:
>                      interrupts = <11 IRQ_TYPE_EDGE_FALLING>;
>                      interrupt-controller;
>                      #interrupt-cells = <1>;
> +
> +                    ec_pwm: pwm {
> +                            compatible = "netronix,ntxec-pwm";
> +                            #pwm-cells = <1>;
shouldn't that be 2?
> +                    };
>              };
>      };
> +
> +    backlight {
> +            compatible = "pwm-backlight";
> +            pwms = <&ec_pwm 0 50000>;
since you have 2 values after the &ec_pwm 

> +    };
> diff --git a/Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml b/Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml
> new file mode 100644
> index 0000000000000..1dc1b1aba081c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml
> @@ -0,0 +1,33 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pwm/netronix,ntxec-pwm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: PWM functionality in Netronix embedded controller
> +
> +maintainers:
> +  - Jonathan Neuschäfer <j.neuschaefer@....net>
> +
> +description: |
> +  See also Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> +
> +  The Netronix EC contains PWM functionality, which is usually used to drive
> +  the backlight LED.
> +
> +  The following PWM channels are supported:
> +    - 0: The PWM channel controlled by registers 0xa1-0xa7
> +
> +allOf:
> +  - $ref: pwm.yaml#
> +
> +properties:
> +  compatible:
> +    const: netronix,ntxec-pwm
> +
> +  "#pwm-cells":
> +    const: 1

shouln't that be 2?
> +
> +required:
> +  - compatible
> +  - "#pwm-cells"
> --
> 2.27.0
> 
> 

Regards,
Andreas