On Mon, 14 Jan 2013, Joe Perches wrote:
> On Fri, 2013-01-11 at 13:12 +0000, Lee Jones wrote:
> > Doing so provides a greater degree of accuracy when dealing with
> > time-frames between 1us and 20ms. msleep() is only accurate for
> > wake-ups greater than 20ms.
> []
> > diff --git a/drivers/power/ab8500_fg.c b/drivers/power/ab8500_fg.c
> []
> > @@ -956,7 +956,7 @@ static int ab8500_fg_load_comp_volt_to_capacity(struct
> > ab8500_fg *di)
> > do {
> > vbat += ab8500_fg_bat_voltage(di);
> > i++;
> > - msleep(5);
> > + usleep_range(5000, 5001);
>
> If you're going to give a range that small
> you might as well use usleep instead.
>
> Otherwise, add some tolerance to allow any
> other coalesced wakeup to occur.
I can't increase the tolerance, as I don't know how that would
effect the running of the system, and the person who would know
is off on parental leave.
What I can tell you is we're only using usleep_range() because
there is no usleep in the kernel. At least that's what we've
been led to believe:
Documentation/timers/timers-howto.txt:
- Why is there no "usleep" / What is a good range?
Since usleep_range is built on top of hrtimers, the
wakeup will be very precise (ish), thus a simple
usleep function would likely introduce a large number
of undesired interrupts.
--
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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