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From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Lothar =?ISO-8859-1?Q?Wa=DFmann?= <LW@karo-electronics.de>,
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Subject: Re: [PATCH 2/2] pwm: imx: support polarity inversion
Date: Mon, 13 Jan 2014 12:13:58 +0100
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On Monday 13 January 2014 11:29:48 Lothar Waßmann wrote:

> diff --git a/arch/arm/boot/dts/imx50.dtsi b/arch/arm/boot/dts/imx50.dtsi
> index 01c0499..e3647a8 100644
> --- a/arch/arm/boot/dts/imx50.dtsi
> +++ b/arch/arm/boot/dts/imx50.dtsi
> @@ -273,7 +273,7 @@
>  			};
>  
>  			pwm1: pwm@53fb4000 {
> -				#pwm-cells = <2>;
> +				#pwm-cells = <3>;
>  				compatible = "fsl,imx50-pwm", "fsl,imx27-pwm";
>  				reg = <0x53fb4000 0x4000>;
>  				clocks = <&clks IMX5_CLK_PWM1_IPG_GATE>,
...
> @@ -271,6 +293,13 @@ static int imx_pwm_probe(struct platform_device *pdev)
>  		return PTR_ERR(imx->mmio_base);
>  
>  	data = of_id->data;
> +	if (data->output_polarity) {
> +		dev_info(&pdev->dev, "PWM supports inversion\n");
> +		imx_pwm_ops.set_polarity = imx_pwm_set_polarity;
> +		imx->chip.of_xlate = of_pwm_xlate_with_flags;
> +		imx->chip.of_pwm_n_cells = 3;
> +	}
> +
>  	imx->config = data->config;
>  	imx->set_enable = data->set_enable;

This looks like you are breaking compatibility with the binding,
which requires #pwm-cells to be <2>. You can extend the binding
to allow both <2> and <3>, but then you have to not only document
that change in the binding, but also ensure that the pwm driver
is able to use either variant.

	Arnd