Andrew Lunn wrote: > As i said in my last email, the AT91 system controller has a different > watchdog timer than the older devices. This patch contains a driver > for this new hardware. > > A couple of points to note: > > 1) The watchdog timer is driven by the slow clock of the AT91. This is > an LC oscillator on the chip. The accuracy of this oscillator is > dependent on silicon process at manufacturing time and the > temperature. I found that my development board a watchdog timeout of > 1000ms actually goes off at around 550ms at room temperature. So be > generous with your timeouts. This also means that one of the test case > fails because the timer goes off too early.
Is it possible to measure the rate of this clock at boot time? By comparing its rate against that of a more accurate clock, for example. If not, I think you should consider adding a sufficiently a large fudge factor so that the watchdog never goes off early. Presumably the datasheet provides minimum and maximum values for the rate of this slow clock? David Vrabel -- David Vrabel, Design Engineer Arcom, Clifton Road Tel: +44 (0)1223 411200 ext. 3233 Cambridge CB1 7EA, UK Web: http://www.arcom.com/
