[PATCH v2 2/5] pwm: imx27: move constant PWMCR register values into probe

[Marco Felsch]

The STOPEN, DOZEN, WAITEN, DBGEN and the CLKSRC bit values never change.
So it should be safe to move this bit settings into probe() and change
only the necessary bits during apply(). Therefore I added the
pwm_imx27_update_bits() helper.

Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
---
v2:
- drop software reset from the logic
- fix setting STOPEN, DOZEN, WAITEN and DBGEN bits in case the pwm is
  already enabled

 drivers/pwm/pwm-imx27.c | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index 7edac4ac6395..b761764b8375 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -96,6 +96,16 @@ struct pwm_imx27_chip {
 
 #define to_pwm_imx27_chip(chip)	container_of(chip, struct pwm_imx27_chip, chip)
 
+static void pwm_imx27_update_bits(void __iomem *reg, u32 mask, u32 val)
+{
+	u32 tmp;
+
+	tmp = readl(reg);
+	tmp &= ~mask;
+	tmp |= val & mask;
+	return writel(tmp, reg);
+}
+
 static int pwm_imx27_clk_prepare_enable(struct pwm_imx27_chip *imx)
 {
 	int ret;
@@ -221,7 +231,7 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	unsigned long long c;
 	unsigned long long clkrate;
 	int ret;
-	u32 cr;
+	u32 cr, mask;
 
 	ret = pwm_imx27_clk_prepare_enable(imx);
 	if (ret)
@@ -267,10 +277,7 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	 */
 	imx->duty_cycle = duty_cycles;
 
-	cr = MX3_PWMCR_PRESCALER_SET(prescale) |
-	     MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
-	     FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) |
-	     MX3_PWMCR_DBGEN;
+	cr = MX3_PWMCR_PRESCALER_SET(prescale);
 
 	if (state->polarity == PWM_POLARITY_INVERSED)
 		cr |= FIELD_PREP(MX3_PWMCR_POUTC,
@@ -279,7 +286,9 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (state->enabled)
 		cr |= MX3_PWMCR_EN;
 
-	writel(cr, imx->mmio_base + MX3_PWMCR);
+	mask = MX3_PWMCR_PRESCALER | MX3_PWMCR_POUTC | MX3_PWMCR_EN;
+
+	pwm_imx27_update_bits(imx->mmio_base + MX3_PWMCR, mask, cr);
 
 	if (imx->enabled != state->enabled) {
 		if (state->enabled) {
@@ -314,7 +323,7 @@ static int pwm_imx27_probe(struct platform_device *pdev)
 {
 	struct pwm_imx27_chip *imx;
 	int ret;
-	u32 pwmcr;
+	u32 pwmcr, mask;
 
 	imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
 	if (imx == NULL)
@@ -361,10 +370,20 @@ static int pwm_imx27_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	/* keep clks on if pwm is running */
+	mask = MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
+	       MX3_PWMCR_DBGEN;
+	pwmcr = MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
+		MX3_PWMCR_DBGEN;
+	pwm_imx27_update_bits(imx->mmio_base + MX3_PWMCR, mask, pwmcr);
+
+	/* keep clks on and clk settings unchanged if pwm is running */
 	pwmcr = readl(imx->mmio_base + MX3_PWMCR);
-	if (!(pwmcr & MX3_PWMCR_EN))
+	if (!(pwmcr & MX3_PWMCR_EN)) {
+		mask = MX3_PWMCR_CLKSRC;
+		pwmcr = FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH);
+		pwm_imx27_update_bits(imx->mmio_base + MX3_PWMCR, mask, pwmcr);
 		pwm_imx27_clk_disable_unprepare(imx);
+	}
 
 	return pwmchip_add(&imx->chip);
 }
-- 
2.20.1