Question about e300 core decrementer interrupt

[Li Tao]

Hi Johansson,

Thanks for your response

在 2009-09-10四的 11:09 +0200，Kenneth Johansson写道：
> On Wed, 2009-09-09 at 13:43 -0500, Scott Wood wrote:
> > On Wed, Sep 09, 2009 at 01:16:07PM +0200, Kenneth Johansson wrote:
> > > On Tue, 2009-09-08 at 13:48 +0800, Li Tao-B22598 wrote:
> > > > Dear all,
> > > > 
> > > > I have a problem in MPC5121 sleep mode. As you know MPC5121 use e300c4
> > > > core. When I make the e300c4 core into sleep mode, it will return to
> > > > full power mode when the“decrementer interrupt” occurred.
> > > > 
> > > > But in the e300 core reference manual said that the “decrementer
> > > > interrupt”have no effect when e300 core in sleep mode, because the
> > > > time
> > > > base and decrementer are disabled while the core is in sleep mode.
> > > > Can anybody explain about this procedure ?
> > 
> > I'm not specifically familiar with MPC5121, but I'll answer from the
> > perspective of MPC83xx which has a similar core:
> > 
> > The decrementer stops ticking when the core goes to sleep.  However, if a
> > decrementer was already pending (but masked with MSR[EE]) before you
> > enter sleep mode, it will cause a wakeup.
> > 
> > To avoid this, the decrementer is set to a very large value prior to and
> > after disabling interrupts.  See generic_suspend_disable_irqs() in
> > arch/powerpc/kernel/time.c.  Is this not happening for you?  Which kernel
> > version are you using, and what mechanism are you using to go to sleep? 
> > 
> > > I'm a bit irritated that it's not as the "solution" can mean hardware
> > > changes an thus it's potentially expensive.
> > 
> > What sort of hardware changes?
> 
>  I don't want to spread missinformation but this procedure has helped on
> the ads5121 rev3 and two custom boards. 
> 
> the gpio 28,29,30 needs to be low and gpio31 needs to be hi. regardless
> of what is used as wakeup source when the device enters deep sleep
> otherwise you end up in some sort of meta state where you might not wake
> up on anything and you have this 42 second auto wakeup from the
> decrementer. 
I use ads5121 rev4.1 board, the gpio 28,29,30 is low and gpio31 is high.
I find that the RTC is fail too, when I use hwclock -f /dev/rtc0 cmd, it
was always "Wed Dec 31 23:59:59 1969  0.000000 seconds". I measured the
the RTC oscillator is 32.768 kHz, and the VBAT_RTC is 4.2v. I have no
idea about why RTC is fail. 
> 
> Other weired states has also been observed. the PMC module is a bit
> tempremental in this chip.
> 
> 
>