[PATCH 5.10 051/147] regulator: core: Fix off_on_delay handling

Sasha Levin
2026-02-28T18:18:16Z

From: Vincent Whitchurch <vincent.whitchurch@axis.com>

[ Upstream commit a8ce7bd89689997537dd22dcbced46cf23dc19da ]

The jiffies-based off_on_delay implementation has a couple of problems
that cause it to sometimes not actually delay for the required time:

(1) If, for example, the off_on_delay time is equivalent to one jiffy,
and the ->last_off_jiffy is set just before a new jiffy starts,
then _regulator_do_enable() does not wait at all since it checks
using time_before().

(2) When jiffies overflows, the value of "remaining" becomes higher
than "max_delay" and the code simply proceeds without waiting.

Fix these problems by changing it to use ktime_t instead.

[Note that since jiffies doesn't start at zero but at INITIAL_JIFFIES
("-5 minutes"), (2) above also led to the code not delaying if
the first regulator_enable() is called when the ->last_off_jiffy is not
initialised, such as for regulators with ->constraints->boot_on set.
It's not clear to me if this was intended or not, but I've preserved
this behaviour explicitly with the check for a non-zero ->last_off.]

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20210423114524.26414-1-vincent.whitchurch@axis.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Stable-dep-of: 86a8eeb0e913 ("regulator: core: move supply check earlier in set_machine_constraints()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/regulator/core.c | 33 ++++++++------------------------
include/linux/regulator/driver.h | 2 +-
2 files changed, 9 insertions(+), 26 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 38c01516d2ed0..3147498948373 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1530,7 +1530,7 @@ static int set_machine_constraints(struct regulator_dev *rdev)
if (rdev->constraints->always_on)
rdev->use_count++;
} else if (rdev->desc->off_on_delay) {
- rdev->last_off_jiffy = jiffies;
+ rdev->last_off = ktime_get();
}

print_constraints(rdev);
@@ -2604,29 +2604,15 @@ static int _regulator_do_enable(struct regulator_dev *rdev)

trace_regulator_enable(rdev_get_name(rdev));

- if (rdev->desc->off_on_delay) {
+ if (rdev->desc->off_on_delay && rdev->last_off) {
/* if needed, keep a distance of off_on_delay from last time
* this regulator was disabled.
*/
- unsigned long start_jiffy = jiffies;
- unsigned long intended, max_delay, remaining;
-
- max_delay = usecs_to_jiffies(rdev->desc->off_on_delay);
- intended = rdev->last_off_jiffy + max_delay;
-
- if (time_before(start_jiffy, intended)) {
- /* calc remaining jiffies to deal with one-time
- * timer wrapping.
- * in case of multiple timer wrapping, either it can be
- * detected by out-of-range remaining, or it cannot be
- * detected and we get a penalty of
- * _regulator_enable_delay().
- */
- remaining = intended - start_jiffy;
- if (remaining <= max_delay)
- _regulator_enable_delay(
- jiffies_to_usecs(remaining));
- }
+ ktime_t end = ktime_add_us(rdev->last_off, rdev->desc->off_on_delay);
+ s64 remaining = ktime_us_delta(end, ktime_get());
+
+ if (remaining > 0)
+ _regulator_enable_delay(remaining);
}

if (rdev->ena_pin) {
@@ -2858,11 +2844,8 @@ static int _regulator_do_disable(struct regulator_dev *rdev)
return ret;
}

- /* cares about last_off_jiffy only if off_on_delay is required by
- * device.
- */
if (rdev->desc->off_on_delay)
- rdev->last_off_jiffy = jiffies;
+ rdev->last_off = ktime_get();

trace_regulator_disable_complete(rdev_get_name(rdev));

diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index 633e7a2ab01d0..a465350427087 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -473,7 +473,7 @@ struct regulator_dev {
unsigned int is_switch:1;

/* time when this regulator was disabled last time */
- unsigned long last_off_jiffy;
+ ktime_t last_off;
};

struct regulator_dev *
--
2.51.0