linux-kernel - Re: [PATCH V3 3/4] pwm: tegra: Add DT binding details to configure pin in suspends/resume

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Date:   Fri, 7 Apr 2017 11:25:35 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Laxman Dewangan <ldewangan@...dia.com>, <thierry.reding@...il.com>,
        <robh+dt@...nel.org>
CC:     <mark.rutland@....com>, <linux-pwm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 3/4] pwm: tegra: Add DT binding details to configure
 pin in suspends/resume


On 07/04/17 10:34, Laxman Dewangan wrote:
> In some of NVIDIA Tegra's platform, PWM controller is used to
> control the PWM controlled regulators. PWM signal is connected to
> the VID pin of the regulator where duty cycle of PWM signal decide
> the voltage level of the regulator output.
> 
> When system enters suspend, some PWM client/slave regulator devices
> require the PWM output to be tristated.
> 
> Add DT binding details to provide the pin configuration state
> from PWM and pinctrl DT node in suspend and active state of
> the system.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
> 
> ---
> Changes from v1:
> - Use standard pinctrl names for sleep and active state.
> 
> Changes from V2:
> - Fix the commit message and details
> ---
>  .../devicetree/bindings/pwm/nvidia,tegra20-pwm.txt | 45 ++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
> index b4e7377..c57e11b 100644
> --- a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
> +++ b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
> @@ -19,6 +19,19 @@ Required properties:
>  - reset-names: Must include the following entries:
>    - pwm
>  
> +Optional properties:
> +============================
> +In some of the interface like PWM based regulator device, it is required
> +to configure the pins differently in different states, especially in suspend
> +state of the system. The configuration of pin is provided via the pinctrl
> +DT node as detailed in the pinctrl DT binding document
> +	Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
> +
> +The PWM node will have following optional properties.
> +pinctrl-names:	Pin state names. Must be "default" and "sleep".
> +pinctrl-0:	phandle for the default/active state of pin configurations.
> +pinctrl-1:	phandle for the sleep state of pin configurations.
> +
>  Example:
>  
>  	pwm: pwm@...0a000 {
> @@ -29,3 +42,35 @@ Example:
>  		resets = <&tegra_car 17>;
>  		reset-names = "pwm";
>  	};
> +
> +
> +Example with the pin configuration for suspend and resume:
> +=========================================================
> +Suppose pin PE7 (On Tegra210) interfaced with the regulator device and
> +it requires PWM output to be tristated when system enters suspend.
> +Following will be DT binding to achieve this:
> +
> +#include <dt-bindings/pinctrl/pinctrl-tegra.h>
> +
> +	pinmux@...008d4 {
> +		pwm_active_state: pwm_active_state {
> +                        pe7 {
> +                                nvidia,pins = "pe7";
> +                                nvidia,tristate = <TEGRA_PIN_DISABLE>;
> +			};
> +		};
> +
> +		pwm_sleep_state: pwm_sleep_state {
> +                        pe7 {
> +                                nvidia,pins = "pe7";
> +                                nvidia,tristate = <TEGRA_PIN_ENABLE>;
> +			};
> +		};
> +	};
> +
> +	pwm@...0a000 {
> +		/* Mandatory PWM properties */

Maybe these are mandatory for the platform, but given these are
optional, its a bit confusing.

> +		pinctrl-names = "default", "sleep";
> +		pinctrl-0 = <&pwm_active_state>;
> +		pinctrl-1 = <&pwm_sleep_state>;
> +	};

However, fine with me so ...

Acked-by: Jon Hunter <jonathanh@...dia.com>

Cheers
Jon

-- 
nvpublic