linux-kernel - Re: [PATCH 2/4] pwm: rockchip: Allow polarity invert on rk3288

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Date:	Tue, 19 Aug 2014 09:18:58 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Heiko Stuebner <heiko@...ech.de>,
	Caesar Wang <caesar.wang@...k-chips.com>,
	Sonny Rao <sonnyrao@...omium.org>, olof@...om.net,
	Eddie Cai <eddie.cai@...k-chips.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] pwm: rockchip: Allow polarity invert on rk3288

On Mon, Aug 18, 2014 at 10:09:07AM -0700, Doug Anderson wrote:
[...]
> diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
>  #define PWM_LP_DISABLE		(0 << 8)
>  
> @@ -32,6 +34,7 @@ struct rockchip_pwm_chip {
>  	struct pwm_chip chip;
>  	struct clk *clk;
>  	const struct rockchip_pwm_data *data;
> +	enum pwm_polarity polarity;

Why do you need this field? struct pwm_device already has a copy of it.

> @@ -74,10 +78,14 @@ static void rockchip_pwm_set_enable_v2(struct pwm_chip *chip, bool enable)
>  {
>  	struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
>  	u32 enable_conf = PWM_OUTPUT_LEFT | PWM_LP_DISABLE | PWM_ENABLE |
> -			  PWM_CONTINUOUS | PWM_DUTY_POSITIVE |
> -			  PWM_INACTIVE_NEGATIVE;
> +			  PWM_CONTINUOUS;
>  	u32 val;
>  
> +	if (pc->polarity == PWM_POLARITY_INVERSED)
> +		enable_conf |= PWM_DUTY_NEGATIVE | PWM_INACTIVE_POSITIVE;
> +	else
> +		enable_conf |= PWM_DUTY_POSITIVE | PWM_INACTIVE_NEGATIVE;

I have a feeling you're going to answer the above question with: "Because
it's needed here". If so, my reply would be: "Then this function should
take a struct pwm_device instead of struct pwm_chip."

> @@ -173,6 +195,7 @@ static const struct rockchip_pwm_data pwm_data_v2 = {
>  		.ctrl = 0x0c,
>  	},
>  	.prescaler = 1,
> +	.has_invert = 1,

Since has_invert is a boolean, the proper value here would be "true".

> @@ -228,6 +252,10 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
>  	pc->data = id->data;
>  	pc->chip.dev = &pdev->dev;
>  	pc->chip.ops = &rockchip_pwm_ops;
> +	if (pc->data->has_invert) {
> +		pc->chip.of_xlate = of_pwm_xlate_with_flags;
> +		pc->chip.of_pwm_n_cells = 3;
> +	}
>  	pc->chip.base = -1;
>  	pc->chip.npwm = 1;

I suggest to rewrite the above as follows for readability:

 	pc->data = id->data;
 	pc->chip.dev = &pdev->dev;
 	pc->chip.ops = &rockchip_pwm_ops;
 	pc->chip.base = -1;
 	pc->chip.npwm = 1;
+
+	if (pc->data->has_invert) {
+		pc->chip.of_xlate = of_pwm_xlate_with_flags;
+		pc->chip.of_pwm_n_cells = 3;
+	}

Thierry

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