Re: [PATCH v6 1/5] powerpc/85xx: implement hardware timebase sync

On Jun 28, 2012, at 5:50 AM, Benjamin Herrenschmidt wrote:

On Thu, 2012-06-28 at 11:38 +0800, Zhao Chenhui wrote:

quoted

=20
=20
The bootloader have done a timebase sync. If we do not need KEXEC or
HOTPLUG_CPU feature, it is unnecessary to do it again at boot time of
kernel. I only compile the timebase sync routines
when users enable KEXEC or HOTPLUG_CPU.=20

=20
Still, how much are you really saving ? Is it worth the added mess and
loss of test coverage ?
=20
We have too many conditional stuff like that already.
=20
Cheers,
Ben.
=20

I'd also be interested to know how long it actually takes to do time =
base sync this way.  Since you are freezing the timers for some period =
how long does it really take between the freeze/unfreeze in =
mpc85xx_give_timebase()

+	mpc85xx_timebase_freeze(1);
...
+	mpc85xx_timebase_freeze(0);

You can use ATBL/U as a way to see # of cycles taken.

- k=