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SubjectRe: [PATCH 3/3] PowerPC/mpc85xx: Add hotplug support on E6500 cores


On Thu, Aug 6, 2015 at 11:16 AM, Scott Wood <scottwood@freescale.com>
wrote:
> On Wed, 2015-08-05 at 19:08 +0800, Chenhui Zhao wrote:
>> On Sat, Aug 1, 2015 at 8:22 AM, Scott Wood <scottwood@freescale.com>
>> wrote:
>> > On Fri, 2015-07-31 at 17:20 +0800, b29983@freescale.comwrote:
>> > > + /*
>> > > + * If both threads are offline, reset core to
>> start.
>> > > + * When core is up, Thread 0 always gets up
>> first,
>> > > + * so bind the current logical cpu with Thread 0.
>> > > + */
>> > > + if (hw_cpu != cpu_first_thread_sibling(hw_cpu)) {
>> > > + int hw_cpu1, hw_cpu2;
>> > > +
>> > > + hw_cpu1 =
>> get_hard_smp_processor_id(primary);
>> > > + hw_cpu2 =
>> get_hard_smp_processor_id(primary +
>> > > 1);
>> > > + set_hard_smp_processor_id(primary,
>> hw_cpu2);
>> > > + set_hard_smp_processor_id(primary + 1,
>> > > hw_cpu1);
>> > > + /* get new physical cpu id */
>> > > + hw_cpu = get_hard_smp_processor_id(nr);
>> >
>> > NACK as discussed in http://patchwork.ozlabs.org/patch/454944/
>> >
>> > -Scott
>>
>> You said,
>>
>> There's no need for this. I have booting from a thread1, and
>> having
>> it
>> kick its thread0, working locally without messing with the
>> hwid/cpu
>> mapping.
>>
>> I still have questions here. After a core reset, how can you boot
>> Thread1
>> of the core first. As I know, Thread0 boots up first by default.
>
> So the issue isn't that thread1 comes up first, but that you *want*
> thread1
> to come up first and it won't. I don't think this remapping is an
> acceptable
> answer, though. Instead, if you need only thread1 to come up, start
> the
> core, have thread0 start thread1, and then send thread0 into whatever
> waiting
> state it would be in if thread1 had never been offlined.
>
> -Scott

Remapping is a concise solution. what's the harm of it?
Keeping things simple is good in my opinion.

-Chenhui





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