[PATCH] ARM: imx: replace imx6q_restart() with mxc_restart()

[Russell King - ARM Linux]

On Tue, Oct 29, 2013 at 09:53:32AM +0100, Lothar Waßmann wrote:
> Hi,
> 
> Shawn Guo wrote:
> > On Mon, Oct 28, 2013 at 10:46:02AM -0700, Olof Johansson wrote:
> > > By the way, the errata document says that you must write it twice
> > > within one 32kHz clock period. You might want to write it three times
> > > just in case two of them happen to straddle that period by pure bad
> > > luck. I'm guessing it's rare enough that you haven't been able to
> > > reproduce it though.
> > 
> > With CPU running at hundred MHz, two writes in the row should not
> > straddle one 32kHz clock period - 31.25 us.
> > 
> But they still may end up in adjacent periods of the 32MHz
> clock. If both writes have to happen within the same period of the
> clock, the third write may be necessary to guarantee this.

Yes, that is correct to the description given.  It's also rather vague
in that it doesn't describe the mechanism for the bug, so we can't say
for certain whether two or three writes are sufficient.

If the problem is to do with a write too close to the 32kHz clock edge,
then two writes should solve it (if the first is too close, the second
one will likely be afterwards).  If the problem is something else, then
three writes would be sensible.

As we don't have this information, I'd suggest using three just to be
sure as Lothar suggests.