linux-kernel - [PATCH v3] pwm: bcm2835: Support apply function for atomic configuration

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Message-Id: <1607464905-16630-1-git-send-email-LinoSanfilippo@gmx.de>
Date:   Tue,  8 Dec 2020 23:01:45 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     thierry.reding@...il.com
Cc:     u.kleine-koenig@...gutronix.de, lee.jones@...aro.org,
        nsaenzjulienne@...e.de, f.fainelli@...il.com, rjui@...adcom.com,
        sean@...s.org, sbranden@...adcom.com,
        bcm-kernel-feedback-list@...adcom.com, linux-pwm@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Lino Sanfilippo <LinoSanfilippo@....de>
Subject: [PATCH v3] pwm: bcm2835: Support apply function for atomic configuration

Use the newer .apply function of pwm_ops instead of .config, .enable,
.disable and .set_polarity. This guarantees atomic changes of the pwm
controller configuration. It also reduces the size of the driver.

Since now period is a 64 bit value, add an extra check to reject periods
that exceed the possible max value for the 32 bit register.

This has been tested on a Raspberry PI 4.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>
---

v3: Check against period truncation (based on a review by Uwe Kleine-König)
v2: Fix compiler error for 64 bit builds

 drivers/pwm/pwm-bcm2835.c | 72 +++++++++++++++++------------------------------
 1 file changed, 26 insertions(+), 46 deletions(-)

diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
index 6841dcf..d339898 100644
--- a/drivers/pwm/pwm-bcm2835.c
+++ b/drivers/pwm/pwm-bcm2835.c
@@ -58,13 +58,15 @@ static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 	writel(value, pc->base + PWM_CONTROL);
 }
 
-static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			      int duty_ns, int period_ns)
+static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			     const struct pwm_state *state)
 {
+
 	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
 	unsigned long rate = clk_get_rate(pc->clk);
+	unsigned long long period;
 	unsigned long scaler;
-	u32 period;
+	u32 val;
 
 	if (!rate) {
 		dev_err(pc->dev, "failed to get clock rate\n");
@@ -72,65 +74,43 @@ static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	}
 
 	scaler = DIV_ROUND_CLOSEST(NSEC_PER_SEC, rate);
-	period = DIV_ROUND_CLOSEST(period_ns, scaler);
+	/* set period */
+	period = DIV_ROUND_CLOSEST_ULL(state->period, scaler);
 
-	if (period < PERIOD_MIN)
+	/* dont accept a period that is too small or has been truncated */
+	if ((period < PERIOD_MIN) || (period > U32_MAX))
 		return -EINVAL;
 
-	writel(DIV_ROUND_CLOSEST(duty_ns, scaler),
-	       pc->base + DUTY(pwm->hwpwm));
-	writel(period, pc->base + PERIOD(pwm->hwpwm));
-
-	return 0;
-}
-
-static int bcm2835_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
-	u32 value;
-
-	value = readl(pc->base + PWM_CONTROL);
-	value |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
-	writel(value, pc->base + PWM_CONTROL);
-
-	return 0;
-}
-
-static void bcm2835_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
-	u32 value;
+	writel((u32) period, pc->base + PERIOD(pwm->hwpwm));
 
-	value = readl(pc->base + PWM_CONTROL);
-	value &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
-	writel(value, pc->base + PWM_CONTROL);
-}
+	/* set duty cycle */
+	val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle, scaler);
+	writel(val, pc->base + DUTY(pwm->hwpwm));
 
-static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
-				enum pwm_polarity polarity)
-{
-	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
-	u32 value;
+	/* set polarity */
+	val = readl(pc->base + PWM_CONTROL);
 
-	value = readl(pc->base + PWM_CONTROL);
+	if (state->polarity == PWM_POLARITY_NORMAL)
+		val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
+	else
+		val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
 
-	if (polarity == PWM_POLARITY_NORMAL)
-		value &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
+	/* enable/disable */
+	if (state->enabled)
+		val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
 	else
-		value |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
+		val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
 
-	writel(value, pc->base + PWM_CONTROL);
+	writel(val, pc->base + PWM_CONTROL);
 
 	return 0;
 }
 
+
 static const struct pwm_ops bcm2835_pwm_ops = {
 	.request = bcm2835_pwm_request,
 	.free = bcm2835_pwm_free,
-	.config = bcm2835_pwm_config,
-	.enable = bcm2835_pwm_enable,
-	.disable = bcm2835_pwm_disable,
-	.set_polarity = bcm2835_set_polarity,
+	.apply = bcm2835_pwm_apply,
 	.owner = THIS_MODULE,
 };
 
-- 
2.7.4