Subject: Re: Cannot wake-up from standby with MPC8313

From: Scott Wood <[email-masked]>
Date: Thu, 5 Jan 2012 12:22:35 -0600

On 01/05/2012 09:58 AM, Norbert van Bolhuis wrote:
> thanks for your response.
> 
> not setting MSR_POW gives same result.

OK, so you're not getting an interrupt regardless of low-power state.

Check whether the interrupt is getting masked during standby preparation.

Does the interrupt handler run when you're not trying to enter standby?

> if I set kernel.powersave-nap=1 it works fine,

What is "it"?  Do you mean that powersave-nap doesn't break things, or
that standby works when you specify that?

> so apparently NAP/DOZE mode does work (if CPU is idle). This saves almost no
> power though. Standby mode saves about 300-500 mW.
> 
> The problem could well be our board though, today I learned it does
> work by connecting an (inactive) JTAG debugger.
> Also, on another board it always works.

You mean connecting a JTAG but not doing anything with it made
wake-from-standby work?

There was a bug like that on early revisions of the mpc8313erdb board --
though in that case if you had a bad board the system would hang
whenever you access any PMC register.  I'm not sure what the mechanism
of failure was; IIRC the fix was adding a resistor.

-Scott