Choosing between DELAY(useconds) and pause()

[John Baldwin]

On Friday, September 23, 2011 11:21:06 am Gavin Atkinson wrote:
> On Thu, 2011-09-22 at 20:07 +0200, Hans Petter Selasky wrote:
> > On Thursday 22 September 2011 19:55:23 David Somayajulu wrote:
> > > It appears that the pause() function cannot be used in driver functions
> > > which are invoked early in the boot process. Is there is a kernel api
> > > which a device driver can use to determine whether to use pause() or
> > > DELAY(), for delays which are say greater than 10hz - may be even 1 hz ?
> > 
> > Maybe you want to use something like this:
> > 
> > if (cold)
> >  DELAY()
> > else
> >  pause()
> > 
> > In your code.
> 
> Note that this still shouldn't be done in your suspend/resume paths, as
> "cold" isn't set there, however there also appears to be no guarantee
> that pause() will ever return (as you could be running after the timer
> has been suspended, or before it resumes).
> 
> I'm not sure what the correct answer is for suspend/resume code.

Hmmm, on x86 the timers are explicitly shutdown after the DEVICE_SUSPEND() 
pass over the tree and re-enabled before DEVICE_RESUME().  Perhaps this has 
changed in HEAD though with the eventtimers stuff.  I do think it is best 
however, to use DELAY() in the suspend/resume path always regardless.

-- 
John Baldwin