Message-Id: <20210329125707.182732-1-clemens.gruber@pqgruber.com>
Date:   Mon, 29 Mar 2021 14:57:01 +0200
From:   Clemens Gruber <clemens.gruber@...ruber.com>
To:     linux-pwm@...r.kernel.org
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Sven Van Asbroeck <TheSven73@...il.com>,
        u.kleine-koenig@...gutronix.de, linux-kernel@...r.kernel.org,
        Clemens Gruber <clemens.gruber@...ruber.com>
Subject: [PATCH v6 1/7] pwm: pca9685: Switch to atomic API

The switch to the atomic API goes hand in hand with a few fixes to
previously experienced issues:
- The duty cycle is no longer lost after disable/enable (previously the
  OFF registers were cleared in disable and the user was required to
  call config to restore the duty cycle settings)
- If one sets a period resulting in the same prescale register value,
  the sleep and write to the register is now skipped

Signed-off-by: Clemens Gruber <clemens.gruber@...ruber.com>
---
Changes since v5:
- Function documentation for set_duty
- Variable initializations
- Print warning if all LEDs channel
- Changed EOPNOTSUPP to EINVAL
- Improved error messages
- Register reset corrections moved to this patch

Changes since v4:
- Patches split up
- Use a single set_duty function
- Improve readability / new macros
- Added a patch to restrict prescale changes to the first user

Changes since v3:
- Refactoring: Extracted common functions
- Read prescale register value instead of caching it
- Return all zeros and disabled for "all LEDs" channel state
- Improved duty calculation / mapping to 0..4096

Changes since v2:
- Always set default prescale value in probe
- Simplified probe code
- Inlined functions with one callsite

Changes since v1:
- Fixed a logic error
- Impoved PM runtime handling and fixed !CONFIG_PM
- Write default prescale reg value if invalid in probe
- Reuse full_off/_on functions throughout driver
- Use cached prescale value whenever possible

 drivers/pwm/pwm-pca9685.c | 261 ++++++++++++++------------------------
 1 file changed, 92 insertions(+), 169 deletions(-)

diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index 4a55dc18656c..0ed1013737e3 100644
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -51,7 +51,6 @@
 #define PCA9685_PRESCALE_MAX	0xFF	/* => min. frequency of 24 Hz */
 
 #define PCA9685_COUNTER_RANGE	4096
-#define PCA9685_DEFAULT_PERIOD	5000000	/* Default period_ns = 1/200 Hz */
 #define PCA9685_OSC_CLOCK_MHZ	25	/* Internal oscillator with 25 MHz */
 
 #define PCA9685_NUMREGS		0xFF
@@ -71,10 +70,14 @@
 #define LED_N_OFF_H(N)	(PCA9685_LEDX_OFF_H + (4 * (N)))
 #define LED_N_OFF_L(N)	(PCA9685_LEDX_OFF_L + (4 * (N)))
 
+#define REG_ON_H(C)	((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_ON_H : LED_N_ON_H((C)))
+#define REG_ON_L(C)	((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_ON_L : LED_N_ON_L((C)))
+#define REG_OFF_H(C)	((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_OFF_H : LED_N_OFF_H((C)))
+#define REG_OFF_L(C)	((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_OFF_L : LED_N_OFF_L((C)))
+
 struct pca9685 {
 	struct pwm_chip chip;
 	struct regmap *regmap;
-	int period_ns;
 #if IS_ENABLED(CONFIG_GPIOLIB)
 	struct mutex lock;
 	struct gpio_chip gpio;
@@ -87,6 +90,51 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip)
 	return container_of(chip, struct pca9685, chip);
 }
 
+/* Helper function to set the duty cycle ratio to duty/4096 (e.g. duty=2048 -> 50%) */
+static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int duty)
+{
+	if (duty == 0) {
+		/* Set the full OFF bit, which has the highest precedence */
+		regmap_write(pca->regmap, REG_OFF_H(channel), LED_FULL);
+	} else if (duty >= PCA9685_COUNTER_RANGE) {
+		/* Set the full ON bit and clear the full OFF bit */
+		regmap_write(pca->regmap, REG_ON_H(channel), LED_FULL);
+		regmap_write(pca->regmap, REG_OFF_H(channel), 0);
+	} else {
+		/* Set OFF time (clears the full OFF bit) */
+		regmap_write(pca->regmap, REG_OFF_L(channel), duty & 0xff);
+		regmap_write(pca->regmap, REG_OFF_H(channel), (duty >> 8) & 0xf);
+		/* Clear the full ON bit */
+		regmap_write(pca->regmap, REG_ON_H(channel), 0);
+	}
+}
+
+static unsigned int pca9685_pwm_get_duty(struct pca9685 *pca, int channel)
+{
+	unsigned int off_h = 0, val = 0;
+
+	if (WARN_ON(channel >= PCA9685_MAXCHAN)) {
+		/* HW does not support reading state of "all LEDs" channel */
+		return 0;
+	}
+
+	regmap_read(pca->regmap, LED_N_OFF_H(channel), &off_h);
+	if (off_h & LED_FULL) {
+		/* Full OFF bit is set */
+		return 0;
+	}
+
+	regmap_read(pca->regmap, LED_N_ON_H(channel), &val);
+	if (val & LED_FULL) {
+		/* Full ON bit is set */
+		return PCA9685_COUNTER_RANGE;
+	}
+
+	val = 0;
+	regmap_read(pca->regmap, LED_N_OFF_L(channel), &val);
+	return ((off_h & 0xf) << 8) | (val & 0xff);
+}
+
 #if IS_ENABLED(CONFIG_GPIOLIB)
 static bool pca9685_pwm_test_and_set_inuse(struct pca9685 *pca, int pwm_idx)
 {
@@ -138,34 +186,23 @@ static int pca9685_pwm_gpio_request(struct gpio_chip *gpio, unsigned int offset)
 static int pca9685_pwm_gpio_get(struct gpio_chip *gpio, unsigned int offset)
 {
 	struct pca9685 *pca = gpiochip_get_data(gpio);
-	struct pwm_device *pwm = &pca->chip.pwms[offset];
-	unsigned int value;
 
-	regmap_read(pca->regmap, LED_N_ON_H(pwm->hwpwm), &value);
-
-	return value & LED_FULL;
+	return pca9685_pwm_get_duty(pca, offset) != 0;
 }
 
 static void pca9685_pwm_gpio_set(struct gpio_chip *gpio, unsigned int offset,
 				 int value)
 {
 	struct pca9685 *pca = gpiochip_get_data(gpio);
-	struct pwm_device *pwm = &pca->chip.pwms[offset];
-	unsigned int on = value ? LED_FULL : 0;
-
-	/* Clear both OFF registers */
-	regmap_write(pca->regmap, LED_N_OFF_L(pwm->hwpwm), 0);
-	regmap_write(pca->regmap, LED_N_OFF_H(pwm->hwpwm), 0);
 
-	/* Set the full ON bit */
-	regmap_write(pca->regmap, LED_N_ON_H(pwm->hwpwm), on);
+	pca9685_pwm_set_duty(pca, offset, value ? PCA9685_COUNTER_RANGE : 0);
 }
 
 static void pca9685_pwm_gpio_free(struct gpio_chip *gpio, unsigned int offset)
 {
 	struct pca9685 *pca = gpiochip_get_data(gpio);
 
-	pca9685_pwm_gpio_set(gpio, offset, 0);
+	pca9685_pwm_set_duty(pca, offset, 0);
 	pm_runtime_put(pca->chip.dev);
 	pca9685_pwm_clear_inuse(pca, offset);
 }
@@ -246,167 +283,56 @@ static void pca9685_set_sleep_mode(struct pca9685 *pca, bool enable)
 	}
 }
 
-static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			      int duty_ns, int period_ns)
+static int pca9685_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			     const struct pwm_state *state)
 {
 	struct pca9685 *pca = to_pca(chip);
-	unsigned long long duty;
-	unsigned int reg;
-	int prescale;
-
-	if (period_ns != pca->period_ns) {
-		prescale = DIV_ROUND_CLOSEST(PCA9685_OSC_CLOCK_MHZ * period_ns,
-					     PCA9685_COUNTER_RANGE * 1000) - 1;
-
-		if (prescale >= PCA9685_PRESCALE_MIN &&
-			prescale <= PCA9685_PRESCALE_MAX) {
-			/*
-			 * Putting the chip briefly into SLEEP mode
-			 * at this point won't interfere with the
-			 * pm_runtime framework, because the pm_runtime
-			 * state is guaranteed active here.
-			 */
-			/* Put chip into sleep mode */
-			pca9685_set_sleep_mode(pca, true);
-
-			/* Change the chip-wide output frequency */
-			regmap_write(pca->regmap, PCA9685_PRESCALE, prescale);
-
-			/* Wake the chip up */
-			pca9685_set_sleep_mode(pca, false);
-
-			pca->period_ns = period_ns;
-		} else {
-			dev_err(chip->dev,
-				"prescaler not set: period out of bounds!\n");
-			return -EINVAL;
-		}
-	}
+	unsigned long long duty, prescale;
+	unsigned int val = 0;
 
-	if (duty_ns < 1) {
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_OFF_H;
-		else
-			reg = LED_N_OFF_H(pwm->hwpwm);
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
 
-		regmap_write(pca->regmap, reg, LED_FULL);
-
-		return 0;
+	prescale = DIV_ROUND_CLOSEST_ULL(PCA9685_OSC_CLOCK_MHZ * state->period,
+					 PCA9685_COUNTER_RANGE * 1000) - 1;
+	if (prescale < PCA9685_PRESCALE_MIN || prescale > PCA9685_PRESCALE_MAX) {
+		dev_err(chip->dev, "pwm not changed: period out of bounds!\n");
+		return -EINVAL;
 	}
 
-	if (duty_ns == period_ns) {
-		/* Clear both OFF registers */
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_OFF_L;
-		else
-			reg = LED_N_OFF_L(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, 0x0);
-
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_OFF_H;
-		else
-			reg = LED_N_OFF_H(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, 0x0);
-
-		/* Set the full ON bit */
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_ON_H;
-		else
-			reg = LED_N_ON_H(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, LED_FULL);
+	duty = PCA9685_COUNTER_RANGE * state->duty_cycle;
+	duty = DIV_ROUND_CLOSEST_ULL(duty, state->period);
 
+	if (!state->enabled || duty < 1) {
+		pca9685_pwm_set_duty(pca, pwm->hwpwm, 0);
+		return 0;
+	} else if (duty == PCA9685_COUNTER_RANGE) {
+		pca9685_pwm_set_duty(pca, pwm->hwpwm, duty);
 		return 0;
 	}
 
-	duty = PCA9685_COUNTER_RANGE * (unsigned long long)duty_ns;
-	duty = DIV_ROUND_UP_ULL(duty, period_ns);
-
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_OFF_L;
-	else
-		reg = LED_N_OFF_L(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, (int)duty & 0xff);
-
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_OFF_H;
-	else
-		reg = LED_N_OFF_H(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, ((int)duty >> 8) & 0xf);
-
-	/* Clear the full ON bit, otherwise the set OFF time has no effect */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_ON_H;
-	else
-		reg = LED_N_ON_H(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0);
-
-	return 0;
-}
-
-static int pca9685_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct pca9685 *pca = to_pca(chip);
-	unsigned int reg;
-
-	/*
-	 * The PWM subsystem does not support a pre-delay.
-	 * So, set the ON-timeout to 0
-	 */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_ON_L;
-	else
-		reg = LED_N_ON_L(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0);
-
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_ON_H;
-	else
-		reg = LED_N_ON_H(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0);
+	regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
+	if (prescale != val) {
+		/*
+		 * Putting the chip briefly into SLEEP mode
+		 * at this point won't interfere with the
+		 * pm_runtime framework, because the pm_runtime
+		 * state is guaranteed active here.
+		 */
+		/* Put chip into sleep mode */
+		pca9685_set_sleep_mode(pca, true);
 
-	/*
-	 * Clear the full-off bit.
-	 * It has precedence over the others and must be off.
-	 */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_OFF_H;
-	else
-		reg = LED_N_OFF_H(pwm->hwpwm);
+		/* Change the chip-wide output frequency */
+		regmap_write(pca->regmap, PCA9685_PRESCALE, (int)prescale);
 
-	regmap_update_bits(pca->regmap, reg, LED_FULL, 0x0);
+		/* Wake the chip up */
+		pca9685_set_sleep_mode(pca, false);
+	}
 
+	pca9685_pwm_set_duty(pca, pwm->hwpwm, duty);
 	return 0;
 }
 
-static void pca9685_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct pca9685 *pca = to_pca(chip);
-	unsigned int reg;
-
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_OFF_H;
-	else
-		reg = LED_N_OFF_H(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, LED_FULL);
-
-	/* Clear the LED_OFF counter. */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_OFF_L;
-	else
-		reg = LED_N_OFF_L(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0x0);
-}
-
 static int pca9685_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct pca9685 *pca = to_pca(chip);
@@ -422,15 +348,13 @@ static void pca9685_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct pca9685 *pca = to_pca(chip);
 
-	pca9685_pwm_disable(chip, pwm);
+	pca9685_pwm_set_duty(pca, pwm->hwpwm, 0);
 	pm_runtime_put(chip->dev);
 	pca9685_pwm_clear_inuse(pca, pwm->hwpwm);
 }
 
 static const struct pwm_ops pca9685_pwm_ops = {
-	.enable = pca9685_pwm_enable,
-	.disable = pca9685_pwm_disable,
-	.config = pca9685_pwm_config,
+	.apply = pca9685_pwm_apply,
 	.request = pca9685_pwm_request,
 	.free = pca9685_pwm_free,
 	.owner = THIS_MODULE,
@@ -461,7 +385,6 @@ static int pca9685_pwm_probe(struct i2c_client *client,
 			ret);
 		return ret;
 	}
-	pca->period_ns = PCA9685_DEFAULT_PERIOD;
 
 	i2c_set_clientdata(client, pca);
 
@@ -484,9 +407,9 @@ static int pca9685_pwm_probe(struct i2c_client *client,
 	reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3);
 	regmap_write(pca->regmap, PCA9685_MODE1, reg);
 
-	/* Clear all "full off" bits */
-	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, 0);
-	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, 0);
+	/* Reset OFF registers to POR default */
+	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, LED_FULL);
+	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, LED_FULL);
 
 	pca->chip.ops = &pca9685_pwm_ops;
 	/* Add an extra channel for ALL_LED */
-- 
2.31.1

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