On Wed, Mar 29, 2017 at 03:56:23PM +0100, Mike Leach wrote:
[...]
> >> > + /*
> >> > + * Unfortunately the CPU cannot be powered up, so return
> >> > + * back and later has no permission to access other
> >> > + * registers. For this case, should set 'idle_constraint'
> >> > + * to ensure CPU power domain is enabled!
> >> > + */
> >> > + if (!(drvdata->edprsr & EDPRSR_PU)) {
> >> > + pr_err("%s: power up request for CPU%d failed\n",
> >> > + __func__, drvdata->cpu);
> >> > + goto out;
> >> > + }
> >> > +
> >> > +out_powered_up:
> >> > + debug_os_unlock(drvdata);
> >> > +
> >> > + /*
> >> > + * At this point the CPU is powered up, so set the no powerdown
> >> > + * request bit so we don't lose power and emulate power down.
> >> > + */
> >> > + drvdata->edprsr = readl(drvdata->base + EDPRCR);
> >> > + drvdata->edprsr |= EDPRCR_COREPURQ | EDPRCR_CORENPDRQ;
> >>
> >> If we are here the core is already up. Shouldn't we need to set
> >> EDPRCR_CORENPDRQ only?
> >
> > Yeah. Will fix.
>
> No - EDPRCR_COREPURQ and EDPRCR_CORENPDRQ have different semantics and purposes
>
> EDPRCR_COREPURQ is in the debug power domain an is tied to an external
> debug request that should be an input to the external (to the PE)
> system power controller.
> The requirement is that the system power controller powers up the core
> domain and does not power it down while it remains asserted.
>
> EDPRCR_CORENPDRQ is in the core power domain and thus to the specific
> core only. This ensures that any power control software running on
> that core should emulate a power down if this is set to one.
I'm curious the exact meaning for "power control software".
Does it mean EDPRCR_CORENPDRQ should be checked by kernel or PSCI
liked code in ARM trusted firmware to avoid to run CPU power off flow?
Or will EDPRCR_CORENPDRQ assert CPU external signal to notify power
controller so power controller emulate a power down?
> We cannot know the power control design of the system, so the safe
> solution is to set both bits.
Thanks a lot for the suggestion. Will set both bits.
Thanks,
Leo Yan
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