Re: [PATCH 1/7] powerpc/85xx: re-enable timebase sync disabled by KEXEC patch

[Kumar Gala <galak@kernel.crashing.org>]

On Nov 4, 2011, at 12:33 PM, Scott Wood wrote:

> On 11/04/2011 07:29 AM, Zhao Chenhui wrote:
>> From: Li Yang <leoli@freescale.com>
>> 
>> The timebase sync is not only necessary when using KEXEC. It should also
>> be used by normal boot up and cpu hotplug. Remove the ifdef added by
>> the KEXEC patch.
> 
> The KEXEC patch didn't just add the ifdef, it also added the initializers:
> 
>> @@ -105,8 +107,64 @@ smp_85xx_setup_cpu(int cpu_nr)
>> 
>> struct smp_ops_t smp_85xx_ops = {
>>        .kick_cpu = smp_85xx_kick_cpu,
>> +#ifdef CONFIG_KEXEC
>> +       .give_timebase  = smp_generic_give_timebase,
>> +       .take_timebase  = smp_generic_take_timebase,
>> +#endif
>> };
> 
> U-Boot synchronizes the timebase on 85xx.  With what chip and U-Boot
> version are you seeing this not happen?
> 
> If you are seeing only a small (around one tick) difference, make sure
> you're running a U-Boot that has this commit:
> 
>> commit 7afc45ad7d9493208d89072cbb78a5bfc8034b59
>> Author: Kumar Gala <galak@kernel.crashing.org>
>> Date:   Sun Mar 13 10:55:53 2011 -0500
>> 
>>    powerpc/85xx: Fix synchronization of timebase on MP boot
>> 
>>    There is a small ordering issue in the master core in that we need to
>>    make sure the disabling of the timebase in the SoC is visible before we
>>    set the value to 0.  We can simply just read back the value to
>>    synchronizatize the write, before we set TB to 0.
>> 
>>    Reported-by: Dan Hettena
>>    Tested-by: Dan Hettena
>>    Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

Scott,

Aren't we going to need this when a core is woken back up w/o any state?

- k