linux-kernel - Re: [PATCH 3/3] PowerPC/mpc85xx: Add hotplug support on E6500 cores

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Date:	Wed, 5 Aug 2015 19:08:26 +0800
From:	Chenhui Zhao <chenhui.zhao@...escale.com>
To:	Scott Wood <scottwood@...escale.com>
CC:	<b29983@...escale.com>, <b07421@...escale.com>,
	<linux-kernel@...r.kernel.org>,
	Tang Yuantian <Yuantian.Tang@...escale.com>,
	Tang Yuantian <Yuantian.Tang@...scale.com>
Subject: Re: [PATCH 3/3] PowerPC/mpc85xx: Add hotplug support on E6500 cores



On Sat, Aug 1, 2015 at 8:22 AM, Scott Wood <scottwood@...escale.com> 
wrote:
> On Fri, 2015-07-31 at 17:20 +0800, b29983@...escale.com wrote:
>>  diff --git a/arch/powerpc/platforms/85xx/smp.c
>>  b/arch/powerpc/platforms/85xx/smp.c
>>  index 7f0dadb..8652a49 100644
>>  --- a/arch/powerpc/platforms/85xx/smp.c
>>  +++ b/arch/powerpc/platforms/85xx/smp.c
>>  @@ -189,15 +189,22 @@ static inline u32 read_spin_table_addr_l(void
>>  *spin_table)
>>   static void wake_hw_thread(void *info)
>>   {
>>        void fsl_secondary_thread_init(void);
>>  -     unsigned long imsr1, inia1;
>>  +     unsigned long imsr, inia;
>>        int nr = *(const int *)info;
>>  -
>>  -     imsr1 = MSR_KERNEL;
>>  -     inia1 = *(unsigned long *)fsl_secondary_thread_init;
>>  -
>>  -     mttmr(TMRN_IMSR1, imsr1);
>>  -     mttmr(TMRN_INIA1, inia1);
>>  -     mtspr(SPRN_TENS, TEN_THREAD(1));
>>  +     int hw_cpu = get_hard_smp_processor_id(nr);
>>  +     int thread_idx = cpu_thread_in_core(hw_cpu);
>>  +
>>  +     booting_cpu_hwid = (u32)hw_cpu;
> 
> Unnecessary cast.  Please explain why you need booting_cpu_hwid.
> 
> 
>>  +     imsr = MSR_KERNEL;
>>  +     inia = *(unsigned long *)fsl_secondary_thread_init;
>>  +     if (thread_idx == 0) {
>>  +             mttmr(TMRN_IMSR0, imsr);
>>  +             mttmr(TMRN_INIA0, inia);
>>  +     } else {
>>  +             mttmr(TMRN_IMSR1, imsr);
>>  +             mttmr(TMRN_INIA1, inia);
>>  +     }
>>  +     mtspr(SPRN_TENS, TEN_THREAD(thread_idx));
> 
> Please rebase this on top of http://patchwork.ozlabs.org/patch/496952/

OK.

> 
> 
>>  +             /*
>>  +              * 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.

-Chenhui





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