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regulator: core: Fix off_on_delay handling

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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>
This commit is contained in:
Vincent Whitchurch 2021-04-23 13:45:24 +02:00 committed by Mark Brown
parent 41a36ffc18
commit a8ce7bd896
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
2 changed files with 8 additions and 25 deletions
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31
drivers/regulator/core.c
View File

@ -1443,7 +1443,7 @@ 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);
@ -2488,29 +2488,15 @@ 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;
ktime_t end = ktime_add_us(rdev->last_off, rdev->desc->off_on_delay);
s64 remaining = ktime_us_delta(end, ktime_get());
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));
}
if (remaining > 0)
_regulator_enable_delay(remaining);
}
if (rdev->ena_pin) {
@ -2740,11 +2726,8 @@ 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));

2
include/linux/regulator/driver.h
View File

@ -476,7 +476,7 @@ 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 *