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Date: Mon, 3 Aug 2015 19:52:04 +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 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and
E500MC cores
On Sat, Aug 1, 2015 at 8:14 AM, Scott Wood <scottwood@...escale.com>
wrote:
> On Fri, 2015-07-31 at 17:20 +0800, b29983@...escale.com wrote:
>> From: Tang Yuantian <Yuantian.Tang@...escale.com>
>>
>> Freescale E500MC and E5500 core-based platforms, like P4080, T1040,
>> support disabling/enabling CPU dynamically.
>> This patch adds this feature on those platforms.
>>
>> Signed-off-by: Chenhui Zhao <chenhui.zhao@...escale.com>
>> Signed-off-by: Tang Yuantian <Yuantian.Tang@...scale.com>
>> ---
>> arch/powerpc/Kconfig | 2 +-
>> arch/powerpc/include/asm/smp.h | 1 +
>> arch/powerpc/kernel/smp.c | 5 +++++
>> arch/powerpc/platforms/85xx/smp.c | 39
>> ++++++++++++++++++++++++++++++++----
>> ---
>> 4 files changed, 39 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 5ef2711..dd9e252 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -386,7 +386,7 @@ config SWIOTLB
>> config HOTPLUG_CPU
>> bool "Support for enabling/disabling CPUs"
>> depends on SMP && (PPC_PSERIES || \
>> - PPC_PMAC || PPC_POWERNV || (PPC_85xx && !PPC_E500MC))
>> + PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE)
>> ---help---
>> Say Y here to be able to disable and re-enable individual
>> CPUs at runtime on SMP machines.
>
>
>
>> diff --git a/arch/powerpc/include/asm/smp.h
>> b/arch/powerpc/include/asm/smp.h
>> index 825663c..bf37d17 100644
>> --- a/arch/powerpc/include/asm/smp.h
>> +++ b/arch/powerpc/include/asm/smp.h
>> @@ -67,6 +67,7 @@ void generic_cpu_die(unsigned int cpu);
>> void generic_set_cpu_dead(unsigned int cpu);
>> void generic_set_cpu_up(unsigned int cpu);
>> int generic_check_cpu_restart(unsigned int cpu);
>> +int generic_check_cpu_dead(unsigned int cpu);
>> #endif
>>
>> #ifdef CONFIG_PPC64
>> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
>> index ec9ec20..2cca27a 100644
>> --- a/arch/powerpc/kernel/smp.c
>> +++ b/arch/powerpc/kernel/smp.c
>> @@ -454,6 +454,11 @@ int generic_check_cpu_restart(unsigned int cpu)
>> return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
>> }
>>
>> +int generic_check_cpu_dead(unsigned int cpu)
>> +{
>> + return per_cpu(cpu_state, cpu) == CPU_DEAD;
>> +}
>
> Is there a non-generic check_cpu_dead()?
NO, just follow the name "generic_check_cpu_restart()".
>
> It gets open-coded in generic_cpu_die()... Either open-code it
> elsewhere, or
> call it check_cpu_dead() and use it everywhere there's a CPU_DEAD
> check.
>
>
>> +
>> static bool secondaries_inhibited(void)
>> {
>> return kvm_hv_mode_active();
>> diff --git a/arch/powerpc/platforms/85xx/smp.c
>> b/arch/powerpc/platforms/85xx/smp.c
>> index 6811a5b..7f0dadb 100644
>> --- a/arch/powerpc/platforms/85xx/smp.c
>> +++ b/arch/powerpc/platforms/85xx/smp.c
>> @@ -42,6 +42,7 @@ struct epapr_spin_table {
>> u32 pir;
>> };
>>
>> +#ifdef CONFIG_HOTPLUG_CPU
>> static u64 timebase;
>> static int tb_req;
>> static int tb_valid;
>> @@ -111,7 +112,7 @@ static void mpc85xx_take_timebase(void)
>> local_irq_restore(flags);
>> }
>>
>> -#ifdef CONFIG_HOTPLUG_CPU
>> +#ifndef CONFIG_PPC_E500MC
>> static void e500_cpu_idle(void)
>
> What happens if we bisect to patch 1/3 and run this on e500mc?
>
> Please move the ifdef to that patch.
OK.
>
>
>> {
>> u32 tmp;
>> @@ -127,6 +128,7 @@ static void e500_cpu_idle(void)
>> mtmsr(tmp);
>> isync();
>> }
>> +#endif
>>
>> static void qoriq_cpu_dying(void)
>> {
>> @@ -144,11 +146,30 @@ static void qoriq_cpu_dying(void)
>>
>> generic_set_cpu_dead(cpu);
>>
>> +#ifndef CONFIG_PPC_E500MC
>> e500_cpu_idle();
>> +#endif
>>
>> while (1)
>> ;
>> }
>> +
>> +static void qoriq_real_cpu_die(unsigned int cpu)
>
> Real as opposed to...?
It's hard to find a good name. :)
>
>
>> +{
>> + int i;
>> +
>> + for (i = 0; i < 50000; i++) {
>> + if (generic_check_cpu_dead(cpu)) {
>> + qoriq_pm_ops->cpu_die(cpu);
>> +#ifdef CONFIG_PPC64
>> + paca[cpu].cpu_start = 0;
>> +#endif
>> + return;
>> + }
>> + udelay(10);
>> + }
>> + pr_err("%s: CPU%d didn't die...\n", __func__, cpu);
>> +}
>
> Only 500ms timeout, versus 10sec in generic_cpu_die()?
The process is fast. Maybe 10 second is too large.
>
>> #endif
>>
>> static inline void flush_spin_table(void *spin_table)
>> @@ -246,11 +267,7 @@ static int smp_85xx_kick_cpu(int nr)
>> spin_table = phys_to_virt(*cpu_rel_addr);
>>
>> local_irq_save(flags);
>> -#ifdef CONFIG_PPC32
>> #ifdef CONFIG_HOTPLUG_CPU
>> - /* Corresponding to generic_set_cpu_dead() */
>> - generic_set_cpu_up(nr);
>> -
>> if (system_state == SYSTEM_RUNNING) {
>> /*
>> * To keep it compatible with old boot program which
>> uses
>> @@ -263,6 +280,7 @@ static int smp_85xx_kick_cpu(int nr)
>> out_be32(&spin_table->addr_l, 0);
>> flush_spin_table(spin_table);
>>
>> + qoriq_pm_ops->cpu_up(nr);
>
> Again, is it possible to get here without a valid qoriq_pm_ops (i.e.
> is there
> anything stopping the user from trying to initiate CPU hotplug)?
>
> -Scott
For every platform running this code, should has a valid qoriq_pm_ops.
If not valid, it's a bug.
-Chenhui
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