Patch "regulator: pwm: Fix regulator ramp delay for continuous mode" has been added to the 4.7-stable tree

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

regulator: pwm: Fix regulator ramp delay for continuous mode

to the 4.7-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:
regulator-pwm-fix-regulator-ramp-delay-for-continuous-mode.patch
and it can be found in the queue-4.7 subdirectory.

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

From: Douglas Anderson <[email protected]>
Date: Wed, 6 Jul 2016 11:42:01 -0700
Subject: regulator: pwm: Fix regulator ramp delay for continuous mode

From: Douglas Anderson <[email protected]>

commit c2588393e6315ab68207323d37d2a73713d6bc81 upstream.

The original commit adding support for continuous voltage mode didn't handle the regulator ramp delay properly. It treated the delay as a fixed delay in uS despite the property being defined as uV / uS. Let's adjust it. Luckily there appear to be no users of this ramp delay for PWM regulators (as per grepping through device trees in linuxnext).

Note also that the upper bound of usleep_range probably shouldn't be a full 1 ms longer than the lower bound since I've seen plenty of hardware with a ramp rate of ~5000 uS / uV and for small jumps the total delays are in the tens of uS. 1000 is way too much. We'll try to be dynamic and use 10%.

NOTE: This commit doesn't add support for regulator-enable-ramp-delay. That could be done in a future patch when someone has a user of that featre.

Though this patch is shows as "fixing" a bug, there are no actual known users of continuous mode PWM regulator w/ ramp delay in mainline and so this likely won't have any effect on anyone unless they are working out-of-tree with private patches. For anyone in this state, it is highly encouraged to also pick Boris Brezillon's WIP patches to get yourself a reliable and glitch-free regulator.

---
 drivers/regulator/pwm-regulator.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

@@ -132,6 +132,7 @@ static int pwm_regulator_set_voltage(str
 	unsigned int duty_pulse;
 	u64 req_period;
 	u32 rem;
+	int old_uV = pwm_regulator_get_voltage(rdev);
 	int ret;
 
 	pwm_get_args(drvdata->pwm, &pargs);

@@ -166,8 +167,12 @@ static int pwm_regulator_set_voltage(str
 	}
 	drvdata->volt_uV = min_uV;
 
-	/* Delay required by PWM regulator to settle to the new voltage */
-	usleep_range(ramp_delay, ramp_delay + 1000);
+	if ((ramp_delay == 0) || !pwm_regulator_is_enabled(rdev))
+		return 0;
+
+	/* Ramp delay is in uV/uS. Adjust to uS and delay */
+	ramp_delay = DIV_ROUND_UP(abs(min_uV - old_uV), ramp_delay);
+	usleep_range(ramp_delay, ramp_delay + DIV_ROUND_UP(ramp_delay, 10));
 
 	return 0;
 }

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

queue-4.7/regulator-pwm-fix-regulator-ramp-delay-for-continuous-mode.patch