[PATCH 13/25] OMAP4: PM: Add WakeupGen module as OMAP gic_arch_extn

On Wednesday 14 September 2011 10:38 PM, Tony Lindgren wrote:

* Santosh[off-list ref]  [110914 09:16]:

quoted

First and foremost, I have to go with the approach here because MPUSS
hardware team put a requirement that GIC and wakeupgen should always be
kept in sync. If needed we can discuss this off-the list with Richard.

Below is the extract from the veyron func specs.
-------------------------------------
Version 1.6 of veyron spec has this.

 From page 95, paragraph 2 on version 1.6:

"It is SW responsibility to program interrupt enabling/disabling
coherently in the GIC and in the Wugen enable registers. That is, a
given interrupt for a given CPU is either enable at both GIC and Wugen,
or disable at both, but no mix."
-------------------------------------

The way understand this IP is, even in normal scenario's every IRQ
will come to wakeupgen and then it will pass that to GIC. CPU clock
domains are kept under HW supervised always and they can enter inactive
any time without WFI. Only wakeup gen can bring the CPU out of inactive
state.

That's requirement really lead to this design choice. Just to add
all ARM SOC's using GIC has a gic extension interrupt controller and
follow the same approach for the secondary IRQCHIPO.

Thanks for the clarification. It seems to me the spec is most likely
wrong as we've had the GIC working for over two years now without
doing anything with the wakeup gen registers :)

It's working because CPU clockdomain are never put under HW
supervised mode and they are kept in force wakeup. Clock-domain
never idles on mainline code. PM series will put the clock-domains
under HW supervison as needed to achieve any low power states and
then all sorts of corner cases will come out.

Regards
Santosh