Re: [PATCH V2 0/6] arm_smp_twd: mpcore_wdt: Fix MPCORE watchdog setup

Catalin Marinas
2011-07-11T09:44:28Z

On Wed, Jul 06, 2011 at 12:16:03PM +0100, Russell King - ARM Linux wrote:
> On Wed, Jul 06, 2011 at 12:05:48PM +0100, Catalin Marinas wrote:
> > On Wed, Jul 06, 2011 at 11:14:56AM +0100, Russell King - ARM Linux wrote:
> > > Do we know why the calibration was initially introduced? FWIR, it came
> > > from the SMP group in ARM, so I guess they had a reason for it rather
> > > than copying x86.
> >
> > I think it was introduced because the TWD frequency is half of the CPU
> > frequency but the latter may not be known - boot monitor configuration
> > could change it.
>
> Okay, that implies we can't have a fixed frequency built into the kernel
> then. For such platforms like the ARM dev boards (realview + vexpress),
> I expect we can read the CPU frequency from somewhere like one of the
> ICST PLLs.

That's highly platform dependent and it's not just ARM dev boards. Any
board with ARM11MPCore, Cortex-A9 or Cortex-A5 would need to find a way
to retrieve such information. If anyone is prepared to go through each
board and figure out how to get the information, it's fine by me.

--
Catalin