Question: ARM: local timers: add num_possible_cpus() in local_timer_register()

[steve.zhan]

Hi,
    Russel, Marc,
2013/1/14 Marc Zyngier <marc.zyngier at arm.com>:
> On 14/01/13 13:33, Steve zhan wrote:
>
> Hi Steve,
>
>>       Do you think we should add num_possible_cpus() in
>> local_timer_register() function, When core number is
>>> 1, then reutrn TRUE? Enable the local timer only if
>> we have more than one CPU, if the current config is
>> SMP and setup_max_cpus >= 1, but if smp_init_cpus in
>> platform code have set cpu possible value to One(that
>> maybe read number from scu or other hardware), then
>> percpu_timer_setup in smp_prepare_cpus have no chance
>> to be called.
>>
>>       For local timer, because local_timer_register have
>> return 1, that will miss global timer register.
>>
>>       Could you pls check it?
>
> I'm not sure I understand your question.
>
> We only enable the use of the SMP local timers infrastructure if we're
> SMP and we have more that one CPU. If you only have one CPU up and
> running, then you can still use your CPU local timer as a global timer.
>
> What would we gain by using the local timer infrastructure when we're
> not running on SMP hardware?
>
>         M.
> --
> Jazz is not dead. It just smells funny...
>

For these code:
        err = local_timer_register(&arch_timer_ops);
        if (err) {
                /*
                 * We couldn't register as a local timer (could be
                 * because we're on a UP platform, or because some
                 * other local timer is already present...). Try as a
                 * global timer instead.
                 */
                arch_timer_global_evt.cpumask = cpumask_of(0);
                err = arch_timer_setup(&arch_timer_global_evt);
        }

if err == 0, we have no register global arch timer,  but platform code
platsmp.c will set
cpu possible number to one, that let percpu_timer_setup in
smp_prepare_cpus have no
chance to call becaue ncores = num_possible_cpus() is one.
Is this right?


-- 
Steve Zhan