lkml.org 
[lkml]   [2017]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] pwm: pca9685: fix prescaler initialization
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: <stable@vger.kernel.org> # v4.3+
> Signed-off-by: Clemens Gruber <clemens.gruber@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
>
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2017-01-18 12:01    [W:0.096 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site