On 07/24/2013 12:49 AM, Viresh Kumar wrote:
Adding more relevant list in cc.
On 23 July 2013 16:05, Ryan <ryanphilip...@googlemail.com> wrote:
Hi,
I have some doubts on backup and restore operation. From what i understand:
We copy all registers values & addresses of all controllers in the SOC
to the internal RAM or SRAM.
before we put CPU to sleep?
I want to know if we also copy the code segment into SRAM and what
happens after wakeup.
If so, where exactly we need to copy and how cpu jumps here after
wakeup. or is there any other mechanism
that is used. What executes first since DDR is in self-refresh.
I use OMAP4 and this is my understanding. I could not understand much
other than in OFF mode
all the controller registers get copied to SRAM. Does anything else
also gets copied too?
or am i missing any basics here.
This understanding is not accurate. OMAP behavior for "OFF mode" is as
follows (as part of suspend/resume):
- drivers do their own "context save" - saving of registers based on
their need.
- SAR registers are saved (note - this is *not* every possible register
on OMAP - but a core subset).
- cpu goes to WFI triggering h/w statemachine flow. (wfi instruction is
in DDR)
- as part of "OFF mode" DDR is put into self refresh automatically
by memory controller.
on wakeup
- core registers are restored by hardware
- DDR is brought out of selfrefresh,
- execution resume in resume function pointer
- drivers restore their own modules as needed.
So, there is no real black magic here :)
--
Regards,
Nishanth Menon
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