linux-kernel - [PATCHv3 3/3] pwm: imx: support output polarity inversion

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Date:	Fri, 28 Mar 2014 09:49:00 +0100
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Thierry Reding <thierry.reding@...il.com>,
	linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
	Lothar Waßmann <LW@...O-electronics.de>,
	Shawn Guo <shawn.guo@...aro.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Arnd Bergmann <arnd@...db.de>
Subject: [PATCHv3 3/3] pwm: imx: support output polarity inversion

The i.MX pwm unit on i.MX27 and newer SoCs provides a configurable
output polarity. This patch adds support to utilize this feature where
available.

Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
---
 drivers/pwm/pwm-imx.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
index 52aac5e..a43410a 100644
--- a/drivers/pwm/pwm-imx.c
+++ b/drivers/pwm/pwm-imx.c
@@ -138,6 +138,8 @@ static int imx_pwm_config_v2(struct pwm_chip *chip,
 
 	if (test_bit(PWMF_ENABLED, &pwm->flags))
 		cr |= MX3_PWMCR_EN;
+	if (pwm->polarity == PWM_POLARITY_INVERSED)
+		cr |= MX3_PWMCR_POUTC;
 
 	writel(cr, imx->mmio_base + MX3_PWMCR);
 
@@ -156,6 +158,11 @@ static void imx_pwm_set_enable_v2(struct pwm_chip *chip, bool enable)
 	else
 		val &= ~MX3_PWMCR_EN;
 
+	if (chip->pwms[0].polarity == PWM_POLARITY_INVERSED)
+		val |= MX3_PWMCR_POUTC;
+	else
+		val &= ~MX3_PWMCR_POUTC;
+
 	writel(val, imx->mmio_base + MX3_PWMCR);
 }
 
@@ -199,6 +206,17 @@ static void imx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 	clk_disable_unprepare(imx->clk_per);
 }
 
+static int imx_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+				enum pwm_polarity polarity)
+{
+	struct imx_chip *imx = to_imx_chip(chip);
+
+	dev_dbg(imx->chip.dev, "%s: polarity set to %s\n", __func__,
+		polarity == PWM_POLARITY_INVERSED ? "inverted" : "normal");
+
+	return 0;
+}
+
 static struct pwm_ops imx_pwm_ops = {
 	.enable = imx_pwm_enable,
 	.disable = imx_pwm_disable,
@@ -210,6 +228,7 @@ struct imx_pwm_data {
 	int (*config)(struct pwm_chip *chip,
 		struct pwm_device *pwm, int duty_ns, int period_ns);
 	void (*set_enable)(struct pwm_chip *chip, bool enable);
+	unsigned output_polarity:1;
 };
 
 static struct imx_pwm_data imx_pwm_data_v1 = {
@@ -220,6 +239,7 @@ static struct imx_pwm_data imx_pwm_data_v1 = {
 static struct imx_pwm_data imx_pwm_data_v2 = {
 	.config = imx_pwm_config_v2,
 	.set_enable = imx_pwm_set_enable_v2,
+	.output_polarity = 1,
 };
 
 static const struct of_device_id imx_pwm_dt_ids[] = {
@@ -272,6 +292,11 @@ static int imx_pwm_probe(struct platform_device *pdev)
 		return PTR_ERR(imx->mmio_base);
 
 	data = of_id->data;
+	if (data->output_polarity) {
+		dev_dbg(&pdev->dev, "PWM supports output inversion\n");
+		imx_pwm_ops.set_polarity = imx_pwm_set_polarity;
+	}
+
 	imx->config = data->config;
 	imx->set_enable = data->set_enable;
 
-- 
1.7.10.4

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