Patch "pwm: pca9685: Fix period change with same duty cycle" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

pwm: pca9685: Fix period change with same duty cycle

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pwm-pca9685-fix-period-change-with-same-duty-cycle.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Clemens Gruber <[email protected]>
Date: Tue, 13 Dec 2016 16:52:50 +0100
Subject: pwm: pca9685: Fix period change with same duty cycle

From: Clemens Gruber <[email protected]>

commit 8d254a340efb12b40c4c1ff25a48a4f48f7bbd6b upstream.

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.

---
 drivers/pwm/pwm-pca9685.c |   11 -----------
 1 file changed, 11 deletions(-)

@@ -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
 			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");

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/pwm-pca9685-fix-period-change-with-same-duty-cycle.patch