Commit 8d254a34 authored Dec 13, 2016 by Clemens Gruber Committed by Thierry Reding Jan 20, 2017

pwm: pca9685: Fix period change with same duty cycle



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: 01ec8472 ("pwm-pca9685: Support changing the output frequency")
Cc: <stable@vger.kernel.org> # v4.3+
Signed-off-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

parent b2ec9efc

drivers/pwm/pwm-pca9685.c

+0 −11

Original line number	Diff line number	Diff line
		@@ -67,7 +67,6 @@
		#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)
		@@ -268,16 +267,6 @@ 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");

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