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

On Thu, Aug 6, 2015 at 1:46 PM, Scott Wood [off-list ref] 
wrote:

On Thu, 2015-08-06 at 12:20 +0800, Chenhui Zhao wrote:

quoted

 On Thu, Aug 6, 2015 at 10:57 AM, Scott Wood 
[off-list ref]
 wrote:
 > On Wed, 2015-08-05 at 18:11 +0800, Chenhui Zhao wrote:
 > >  On Tue, Aug 4, 2015 at 4:26 AM, Scott Wood 
[off-list ref]
 > >  wrote:
 > >  > On Mon, 2015-08-03 at 19:32 +0800, Chenhui Zhao wrote:
 > >  > >  >
 > >  >
 > >  > >  On Sat, Aug 1, 2015 at 7:59 AM, Scott Wood
 > > [off-list ref]
 > >  > >  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.
 >
 > Why would the MPIC be signalling those interrupts if they've been
 > masked at
 > the MPIC?
 >
 > -Scott
 >

 The interrupts to RCPM from MPIC are IRQ, Machine Check, NMI and
 Critical interrupts. Some of them didn't be masked in MPIC.

What interrupt could actually happen to a sleeping cpu that this 
protects
against?

-Scott

Not sure. Maybe spurious interrupts or hardware exceptions. However, 
setting them make sure dead cpus can not be waked up unexpectedly.

-Chenhui