Re: [PATCH 4/7] regulator: add mxs regulator driver

[Stefan Wahren <stefan.wahren@i2se.com>]

Hi Mark,

>
> > + if (ldo->get_power_source)
> > + power_source = ldo->get_power_source(reg);
> > +
> > + switch (power_source) {
> > + case HW_POWER_LINREG_DCDC_OFF:
> > + case HW_POWER_LINREG_DCDC_READY:
> > + case HW_POWER_EXTERNAL_SOURCE_5V:
> > + usleep_range(1000, 2000);
> > + return 0;
> > + }
>
> I'd expect the switch to be in the if here?

yes, that's possible too.

>
> > +
> > + usleep_range(15, 20);
> > + start = jiffies;
> > + while (1) {
> > + if (readl(ldo->status_addr) & BM_POWER_STS_DC_OK)
> > + return 0;
> > +
> > + if (time_after(jiffies, start + msecs_to_jiffies(20)))
> > + break;
> > +
> > + schedule();
> > + }
>
> So, this isn't actually quite a busy wait because we do a schedule()
> rather than a cpu_relax() but still it could devolve into that - 20ms
> seems a long time to burn doing that. If we're expecting this to finish
> very quickly can we do an initial busy wait then fall back to something
> with an actual sleep or soemthing?

We will need to keep the initial usleep_range(). So do you think of the
following:

1. usleep_range
2. busy_wait for BM_POWER_STS_DC_OK
3. msleep (for the timeout case)

Stefan