On Tue, Dec 13, 2016 at 04:52:50PM +0100, Clemens Gruber wrote:
> When first implementing support for changing the output frequency, an
> optimization was added to continue the PWM after changing the prescaler
> without having to reprogram the ON and OFF registers for the duty cycle,
> in case the duty cycle stayed the same.
> This was flawed, because we compared the absolute value of the duty
> cycle in nanoseconds instead of the ratio to the period.
>
> Fix the problem by removing the shortcut.
>
> Fixes: 01ec8472009c9 ("pwm-pca9685: Support changing the output frequency")
> Cc: <sta...@vger.kernel.org> # v4.3+
> Signed-off-by: Clemens Gruber <clemens.gru...@pqgruber.com>
> ---
> drivers/pwm/pwm-pca9685.c | 11 -----------
> 1 file changed, 11 deletions(-)
Mika, Andy, can you guys help review this and 2/2?
Thanks,
Thierry
>
> diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
> index 117fccf..01a6a83 100644
> --- a/drivers/pwm/pwm-pca9685.c
> +++ b/drivers/pwm/pwm-pca9685.c
> @@ -65,7 +65,6 @@
> #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)
> @@ -117,16 +116,6 @@ static int pca9685_pwm_config(struct pwm_chip *chip,
> struct pwm_device *pwm,
> 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");
> --
> 2.10.2
>
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