From: Uwe Kleine-König Date: Tue, 29 Jul 2025 10:36:01 +0000 (+0200) Subject: pwm: pca9685: Use bulk write to atomicially update registers X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=de5855613263b426ee697dd30224322f2e634dec;p=users%2Fhch%2Fmisc.git pwm: pca9685: Use bulk write to atomicially update registers The output of a PWM channel is configured by four register values. Write them in a single i2c transaction to ensure glitch free updates. Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/bfa8c0267c9ec059d0d77f146998d564654c75ca.1753784092.git.u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König --- diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c index de5fe86b4f33..b22c6da20ebc 100644 --- a/drivers/pwm/pwm-pca9685.c +++ b/drivers/pwm/pwm-pca9685.c @@ -61,6 +61,8 @@ #define MODE1_SUB2 BIT(2) #define MODE1_SUB1 BIT(3) #define MODE1_SLEEP BIT(4) +#define MODE1_AI BIT(5) + #define MODE2_INVRT BIT(4) #define MODE2_OUTDRV BIT(2) @@ -131,6 +133,19 @@ static int pca9685_write_reg(struct pwm_chip *chip, unsigned int reg, unsigned i return err; } +static int pca9685_write_4reg(struct pwm_chip *chip, unsigned int reg, u8 val[4]) +{ + struct pca9685 *pca = to_pca(chip); + struct device *dev = pwmchip_parent(chip); + int err; + + err = regmap_bulk_write(pca->regmap, reg, val, 4); + if (err) + dev_err(dev, "regmap_write to register 0x%x failed: %pe\n", reg, ERR_PTR(err)); + + return err; +} + /* Helper function to set the duty cycle ratio to duty/4096 (e.g. duty=2048 -> 50%) */ static void pca9685_pwm_set_duty(struct pwm_chip *chip, int channel, unsigned int duty) { @@ -143,12 +158,10 @@ static void pca9685_pwm_set_duty(struct pwm_chip *chip, int channel, unsigned in return; } else if (duty >= PCA9685_COUNTER_RANGE) { /* Set the full ON bit and clear the full OFF bit */ - pca9685_write_reg(chip, REG_ON_H(channel), LED_FULL); - pca9685_write_reg(chip, REG_OFF_H(channel), 0); + pca9685_write_4reg(chip, REG_ON_L(channel), (u8[4]){ 0, LED_FULL, 0, 0 }); return; } - if (pwm->state.usage_power && channel < PCA9685_MAXCHAN) { /* * If usage_power is set, the pca9685 driver will phase shift @@ -163,12 +176,9 @@ static void pca9685_pwm_set_duty(struct pwm_chip *chip, int channel, unsigned in off = (on + duty) % PCA9685_COUNTER_RANGE; - /* Set ON time (clears full ON bit) */ - pca9685_write_reg(chip, REG_ON_L(channel), on & 0xff); - pca9685_write_reg(chip, REG_ON_H(channel), (on >> 8) & 0xf); - /* Set OFF time (clears full OFF bit) */ - pca9685_write_reg(chip, REG_OFF_L(channel), off & 0xff); - pca9685_write_reg(chip, REG_OFF_H(channel), (off >> 8) & 0xf); + /* implicitly clear full ON and full OFF bit */ + pca9685_write_4reg(chip, REG_ON_L(channel), + (u8[4]){ on & 0xff, (on >> 8) & 0xf, off & 0xff, (off >> 8) & 0xf }); } static unsigned int pca9685_pwm_get_duty(struct pwm_chip *chip, int channel) @@ -543,9 +553,8 @@ static int pca9685_pwm_probe(struct i2c_client *client) mutex_init(&pca->lock); - ret = pca9685_read_reg(chip, PCA9685_MODE2, ®); - if (ret) - return ret; + /* clear MODE2_OCH */ + reg = 0; if (device_property_read_bool(&client->dev, "invert")) reg |= MODE2_INVRT; @@ -561,16 +570,19 @@ static int pca9685_pwm_probe(struct i2c_client *client) if (ret) return ret; - /* Disable all LED ALLCALL and SUBx addresses to avoid bus collisions */ + /* + * Disable all LED ALLCALL and SUBx addresses to avoid bus collisions, + * enable Auto-Increment. + */ pca9685_read_reg(chip, PCA9685_MODE1, ®); reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3); + reg |= MODE1_AI; pca9685_write_reg(chip, PCA9685_MODE1, reg); /* Reset OFF/ON registers to POR default */ - pca9685_write_reg(chip, PCA9685_ALL_LED_OFF_L, 0); - pca9685_write_reg(chip, PCA9685_ALL_LED_OFF_H, LED_FULL); - pca9685_write_reg(chip, PCA9685_ALL_LED_ON_L, 0); - pca9685_write_reg(chip, PCA9685_ALL_LED_ON_H, LED_FULL); + ret = pca9685_write_4reg(chip, PCA9685_ALL_LED_ON_L, (u8[]){ 0, LED_FULL, 0, LED_FULL }); + if (ret < 0) + return dev_err_probe(&client->dev, ret, "Failed to reset ON/OFF registers\n"); chip->ops = &pca9685_pwm_ops;