linux-kernel - Re: [PATCH 1/3] Powerpc: mpc85xx: refactor the PM operations

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Date:	Mon, 3 Aug 2015 19:32:58 +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 1/3] Powerpc: mpc85xx: refactor the PM operations



On Sat, Aug 1, 2015 at 7:59 AM, Scott Wood <scottwood@...escale.com> 
wrote:
> On Fri, 2015-07-31 at 17:20 +0800, b29983@...escale.com wrote:
>>  @@ -71,7 +56,7 @@ static void mpc85xx_give_timebase(void)
>>                barrier();
>>        tb_req = 0;
>> 
>>  -     mpc85xx_timebase_freeze(1);
>>  +     qoriq_pm_ops->freeze_time_base(1);
> 
> freeze_time_base() takes a bool.  Use true/false.

OK.

> 
> 
>>   #ifdef CONFIG_PPC64
>>        /*
>>         * e5500/e6500 have a workaround for erratum A-006958 in place
>>  @@ -104,7 +89,7 @@ static void mpc85xx_give_timebase(void)
>>        while (tb_valid)
>>                barrier();
>> 
>>  -     mpc85xx_timebase_freeze(0);
>>  +     qoriq_pm_ops->freeze_time_base(0);
>> 
>>        local_irq_restore(flags);
>>   }
>>  @@ -127,20 +112,10 @@ static void mpc85xx_take_timebase(void)
>>   }
>> 
>>   #ifdef CONFIG_HOTPLUG_CPU
>>  -static void smp_85xx_mach_cpu_die(void)
>>  +static void e500_cpu_idle(void)
> 
> This is not the function that gets called during normal cpu idle, and 
> it
> shouldn't be named to look like it is.

Sorry, it's a typo. It shoule be "e500_cpu_die".

> 
>>   {
>>  -     unsigned int cpu = smp_processor_id();
>>        u32 tmp;
>> 
>>  -     local_irq_disable();
>>  -     idle_task_exit();
>>  -     generic_set_cpu_dead(cpu);
>>  -     mb();
>>  -
>>  -     mtspr(SPRN_TCR, 0);
>>  -
>>  -     cur_cpu_spec->cpu_down_flush();
>>  -
>>        tmp = (mfspr(SPRN_HID0) & ~(HID0_DOZE|HID0_SLEEP)) | HID0_NAP;
>>        mtspr(SPRN_HID0, tmp);
>>        isync();
>>  @@ -151,6 +126,25 @@ static void smp_85xx_mach_cpu_die(void)
>>        mb();
>>        mtmsr(tmp);
>>        isync();
>>  +}
>>  +
>>  +static void qoriq_cpu_dying(void)
>>  +{
>>  +     unsigned int cpu = smp_processor_id();
>>  +
>>  +     hard_irq_disable();
>>  +     /* mask all irqs to prevent cpu wakeup */
>>  +     qoriq_pm_ops->irq_mask(cpu);
>>  +     idle_task_exit();
>>  +
>>  +     mtspr(SPRN_TCR, 0);
>>  +     mtspr(SPRN_TSR, mfspr(SPRN_TSR));
>>  +
>>  +     cur_cpu_spec->cpu_down_flush();
>>  +
>>  +     generic_set_cpu_dead(cpu);
>>  +
>>  +     e500_cpu_idle();
> 
> Why is something that claims to be applicable to all qoriq directly 
> calling
> an e500v2-specific function?

Added "#ifndef CONFIG_PPC_E500MC" in the following patch.

> 
> Could you explain irq_mask()?  Why would there still be IRQs destined 
> for
> this CPU at this point?

This function just masks irq by setting the registers in RCPM (for 
example, RCPM_CPMIMR, RCPM_CPMCIMR). Actually, all irqs to this CPU 
have been migrated to other CPUs.

> 
> @@ -431,21 +415,9 @@ void __init mpc85xx_smp_init(void)
>>                smp_85xx_ops.probe = NULL;
>>        }
>> 
>>  -     np = of_find_matching_node(NULL, mpc85xx_smp_guts_ids);
>>  -     if (np) {
>>  -             guts = of_iomap(np, 0);
>>  -             of_node_put(np);
>>  -             if (!guts) {
>>  -                     pr_err("%s: Could not map guts node 
>> address\n",
>>  -                                                             
>> __func__);
>>  -                     return;
>>  -             }
>>  -             smp_85xx_ops.give_timebase = mpc85xx_give_timebase;
>>  -             smp_85xx_ops.take_timebase = mpc85xx_take_timebase;
>>   #ifdef CONFIG_HOTPLUG_CPU
>>  -             ppc_md.cpu_die = smp_85xx_mach_cpu_die;
>>  +     ppc_md.cpu_die = qoriq_cpu_dying;
>>   #endif
> 
> Shouldn't you make sure there's a valid qoriq_pm_ops before setting
> cpu_die()?  Or make sure that qoriq_cpu_dying() works regardless.
> 
> -Scott

This patch is just for e500v2. The following patches will handle the 
case of e500mc, e5500 and e6500.

-Chenhui

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