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

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Date:	Wed, 5 Aug 2015 18:11:17 +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 Tue, Aug 4, 2015 at 4:26 AM, Scott Wood <scottwood@...escale.com> 
wrote:
> On Mon, 2015-08-03 at 19:32 +0800, Chenhui Zhao wrote:
>>  >
> 
>>  On Sat, Aug 1, 2015 at 7:59 AM, Scott Wood <scottwood@...escale.com>
>>  wrote:
> 
>>  >
>>  > 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.
> 
> So why do we need to set those bits in RCPM?  Is it just caution?

Setting these bits can mask interrupts signalled to RCPM from MPIC as a 
means of
waking up from a lower power state. So, cores will not be waked up 
unexpectedly.

> 
>>  > @@ -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.
> 
> What stops a user from trying to use cpu hotplug on unsupported cpus, 
> or in a
> virtualized environment, and crashing here?
> 
> -Scott

Will set these callback functions only if qoriq_pm_ops is valid.

-Chenhui

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