Re: [PATCH v2 09/21] ARM: pxa: magician: Add OV9640 camera support

Arnd Bergmann
2015-08-21T13:46:16Z

On Friday 21 August 2015 00:39:30 Petr Cvek wrote:
> Dne 20.8.2015 v 22:26 Arnd Bergmann napsal(a):
> > On Thursday 20 August 2015 21:48:20 Robert Jarzmik wrote:
> >> Petr Cvek <petr.cvek@tul.cz> writes:
> >>
> >>> + mdelay(3);
> >> Okay, there are several mdelay(3) in this file.
> >>
> >> Could you please test if removing these mdelays prevents the camera from working
> >> ? If not, I'd like to have them removed.
> >>
> >>
> >
> > FWIW, it might be possible to replace some of them with msleep() calls,
> > potentially after replacing spinlocks with mutexes where necessary.
> >
> > Arnd
> >
>
> Datasheet says:
>
> tS:RESET Setting time after software/hardware reset 1 ms
>
> So at least one ~1 ms should be left there. Are msleep less than 20ms valid?
>
> (checkpatch: msleep < 20ms can sleep for up to 20ms)

On most kernels, an msleep(1) will sleep somewhere between 1 and 3 milliseconds
(but could be much longer), while an mdelay(1) tries to sleep around one
millisecond, more or less.

Arnd