Patch "pwm: pca9685: Fix period change with same duty cycle" has been added to the 4.10-stable tree

Patch "pwm: pca9685: Fix period change with same duty cycle" has been added to the 4.10-stable tree

[gregkh]

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 4.10-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-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8d254a340efb12b40c4c1ff25a48a4f48f7bbd6b Mon Sep 17 00:00:00 2001
From: Clemens Gruber <clemens.gruber@pqgruber.com>
Date: Tue, 13 Dec 2016 16:52:50 +0100
Subject: pwm: pca9685: Fix period change with same duty cycle

From: Clemens Gruber <clemens.gruber@pqgruber.com>

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.

Fixes: 01ec8472009c9 ("pwm-pca9685: Support changing the output frequency")
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- 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
 			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 clemens.gruber@pqgruber.com are

queue-4.10/pwm-pca9685-fix-period-change-with-same-duty-cycle.patch