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regulator: core: Reduce busy-wait looping

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Keep busy-wait looping to a minimum while waiting for a regulator to
ramp-up to the target voltage. This follows the guidelines set forth
in Documentation/timers/timers-howto.txt and assumes that regulators
are never enabled in atomic context.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
This commit is contained in:
Thierry Reding 2013-09-20 13:51:56 +02:00 committed by Mark Brown
parent 043c998f95
commit 5df529d440
1 changed files with 33 additions and 5 deletions
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38
drivers/regulator/core.c
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@ -1740,11 +1740,39 @@ static int _regulator_do_enable(struct regulator_dev *rdev)
* together. */
trace_regulator_enable_delay(rdev_get_name(rdev));
if (delay >= 1000) {
mdelay(delay / 1000);
udelay(delay % 1000);
} else if (delay) {
udelay(delay);
/*
* Delay for the requested amount of time as per the guidelines in:
*
* Documentation/timers/timers-howto.txt
*
* The assumption here is that regulators will never be enabled in
* atomic context and therefore sleeping functions can be used.
*/
if (delay) {
unsigned int ms = delay / 1000;
unsigned int us = delay % 1000;
if (ms > 0) {
/*
* For small enough values, handle super-millisecond
* delays in the usleep_range() call below.
*/
if (ms < 20)
us += ms * 1000;
else
msleep(ms);
}
/*
* Give the scheduler some room to coalesce with any other
* wakeup sources. For delays shorter than 10 us, don't even
* bother setting up high-resolution timers and just busy-
* loop.
*/
if (us >= 10)
usleep_range(us, us + 100);
else
udelay(us);
}
trace_regulator_enable_complete(rdev_get_name(rdev));