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path: root/drivers/pwm/pwm-pca9685.c
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Diffstat (limited to 'drivers/pwm/pwm-pca9685.c')
-rw-r--r--drivers/pwm/pwm-pca9685.c90
1 files changed, 88 insertions, 2 deletions
diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index 34b5c275a..70448a607 100644
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -2,6 +2,7 @@
* Driver for PCA9685 16-channel 12-bit PWM LED controller
*
* Copyright (C) 2013 Steffen Trumtrar <s.trumtrar@pengutronix.de>
+ * Copyright (C) 2015 Clemens Gruber <clemens.gruber@pqgruber.com>
*
* based on the pwm-twl-led.c driver
*
@@ -24,6 +25,15 @@
#include <linux/pwm.h>
#include <linux/regmap.h>
#include <linux/slab.h>
+#include <linux/delay.h>
+
+/*
+ * Because the PCA9685 has only one prescaler per chip, changing the period of
+ * one channel affects the period of all 16 PWM outputs!
+ * However, the ratio between each configured duty cycle and the chip-wide
+ * period remains constant, because the OFF time is set in proportion to the
+ * counter range.
+ */
#define PCA9685_MODE1 0x00
#define PCA9685_MODE2 0x01
@@ -42,10 +52,18 @@
#define PCA9685_ALL_LED_OFF_H 0xFD
#define PCA9685_PRESCALE 0xFE
+#define PCA9685_PRESCALE_MIN 0x03 /* => max. frequency of 1526 Hz */
+#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
#define PCA9685_MAXCHAN 0x10
#define LED_FULL (1 << 4)
+#define MODE1_RESTART (1 << 7)
#define MODE1_SLEEP (1 << 4)
#define MODE2_INVRT (1 << 4)
#define MODE2_OUTDRV (1 << 2)
@@ -59,6 +77,8 @@ struct pca9685 {
struct pwm_chip chip;
struct regmap *regmap;
int active_cnt;
+ int duty_ns;
+ int period_ns;
};
static inline struct pca9685 *to_pca(struct pwm_chip *chip)
@@ -72,6 +92,47 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
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) {
+ /* Put chip into sleep mode */
+ regmap_update_bits(pca->regmap, PCA9685_MODE1,
+ MODE1_SLEEP, MODE1_SLEEP);
+
+ /* Change the chip-wide output frequency */
+ regmap_write(pca->regmap, PCA9685_PRESCALE, prescale);
+
+ /* Wake the chip up */
+ regmap_update_bits(pca->regmap, PCA9685_MODE1,
+ MODE1_SLEEP, 0x0);
+
+ /* Wait 500us for the oscillator to be back up */
+ udelay(500);
+
+ pca->period_ns = period_ns;
+
+ /*
+ * If the duty cycle did not change, restart PWM with
+ * the same duty cycle to period ratio and return.
+ */
+ if (duty_ns == pca->duty_ns) {
+ regmap_update_bits(pca->regmap, PCA9685_MODE1,
+ MODE1_RESTART, 0x1);
+ return 0;
+ }
+ } else {
+ dev_err(chip->dev,
+ "prescaler not set: period out of bounds!\n");
+ return -EINVAL;
+ }
+ }
+
+ pca->duty_ns = duty_ns;
if (duty_ns < 1) {
if (pwm->hwpwm >= PCA9685_MAXCHAN)
@@ -85,6 +146,22 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
}
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
@@ -95,7 +172,7 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
return 0;
}
- duty = 4096 * (unsigned long long)duty_ns;
+ duty = PCA9685_COUNTER_RANGE * (unsigned long long)duty_ns;
duty = DIV_ROUND_UP_ULL(duty, period_ns);
if (pwm->hwpwm >= PCA9685_MAXCHAN)
@@ -112,6 +189,14 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
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;
}
@@ -228,6 +313,8 @@ static int pca9685_pwm_probe(struct i2c_client *client,
ret);
return ret;
}
+ pca->duty_ns = 0;
+ pca->period_ns = PCA9685_DEFAULT_PERIOD;
i2c_set_clientdata(client, pca);
@@ -285,7 +372,6 @@ MODULE_DEVICE_TABLE(of, pca9685_dt_ids);
static struct i2c_driver pca9685_i2c_driver = {
.driver = {
.name = "pca9685-pwm",
- .owner = THIS_MODULE,
.of_match_table = pca9685_dt_ids,
},
.probe = pca9685_pwm_probe,