On Tue, Dec 13, 2016 at 04:52:51PM +0100, Clemens Gruber wrote: > 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: <sta...@vger.kernel.org> # v4.3+ > Signed-off-by: Clemens Gruber <clemens.gru...@pqgruber.com> > --- > drivers/pwm/pwm-pca9685.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-)
Cc'ing Mika and Andy and quoting verbatim for review.
Thierry
> 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
>
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