Subject: [PATCH 04/18] power: ab8500_fg: Replace msleep() with usleep_range() for greater accuracy

From: [email-masked] (Arnd Bergmann)
Date: Tue, 15 Jan 2013 13:23:28 +0000

On Tuesday 15 January 2013, Lee Jones wrote:
> > > @@ -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.

The function only averages the voltage between a couple of readings.
It won't change much if those register reads are slightly more
uniformly timed. Note that the thread can still be preempted for
a much longer time if anything else is running, and the entire
interrupt handling in this driver looks so fragile that I would
not rely on the interrupt actually happening at the right time
anyway. I think it should first be debugged properly to remove
the need for the enable_irq/disable_irq calls.

	Arnd