Until now, we assumed that the period is the hardware default of 1/200Hz at probe time, but if the period was changed and the user reboots, this assumption is wrong.
Solution: Check if the prescaler is set to the hardware default. If not, reprogram the prescaler at first configuration. Cc: <[email protected]> # v4.3+ Signed-off-by: Clemens Gruber <[email protected]> --- drivers/pwm/pwm-pca9685.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c index 01a6a83..efc657e 100644 --- a/drivers/pwm/pwm-pca9685.c +++ b/drivers/pwm/pwm-pca9685.c @@ -55,6 +55,7 @@ #define PCA9685_PRESCALE 0xFE #define PCA9685_PRESCALE_MIN 0x03 /* => max. frequency of 1526 Hz */ +#define PCA9685_PRESCALE_DEF 0x1E /* => default frequency of 200 Hz */ #define PCA9685_PRESCALE_MAX 0xFF /* => min. frequency of 24 Hz */ #define PCA9685_COUNTER_RANGE 4096 @@ -289,8 +290,8 @@ static int pca9685_pwm_probe(struct i2c_client *client, const struct i2c_device_id *id) { struct pca9685 *pca; + int prescale, mode2; int ret; - int mode2; pca = devm_kzalloc(&client->dev, sizeof(*pca), GFP_KERNEL); if (!pca) @@ -304,10 +305,15 @@ static int pca9685_pwm_probe(struct i2c_client *client, return ret; } pca->duty_ns = 0; - pca->period_ns = PCA9685_DEFAULT_PERIOD; i2c_set_clientdata(client, pca); + regmap_read(pca->regmap, PCA9685_PRESCALE, &prescale); + if (prescale == PCA9685_PRESCALE_DEF) + pca->period_ns = PCA9685_DEFAULT_PERIOD; + else + pca->period_ns = 0; + regmap_read(pca->regmap, PCA9685_MODE2, &mode2); if (device_property_read_bool(&client->dev, "invert")) -- 2.10.2
