diff options
| -rw-r--r-- | drivers/pwm/pwm-pca9685.c | 65 |
1 files changed, 64 insertions, 1 deletions
diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c index 0d17d99b749b..70448a6079b0 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) @@ -111,7 +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) @@ -252,6 +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); |