implementing "suspend to ram" on cortex A8 based on linux 3.0.8

Chenglie He chengjie.he at
Fri Mar 9 14:08:30 UTC 2012


I am doing this on A9, echo mem >/sys/power/state is right, will trigger
kernel to sleep.


On 7 March 2012 23:05, yang gqyang <hustgqyang at> wrote:

> dear all:
> I am working on arm cortex a8 now, trying to implement "suspend to ram"
> based on linux 3.0.8.
> Before i start my work, the soc already support standby(the cpu is on wfi
> state), so in order to implement "suspend to ram", i think i just need to
> implement the arch-specific related api. The "suspend to ram" works like
> this:
> "echo mem > /sys/power/state"  -> enter_state -> suspend_devices_and_enter
> ->suspend_ops->enter(state)
>  Is that right? Do you think the "suspend to ram" can be realized in this
> way?
>  In order to power off the cortex A8, i save all the writable
> co-processor and   all modes's state register set, and restore them when
> resuming.
>  All the code seems work ok, because when I just does not power off the
> cortex-A8 and jump to excute the resume code, the system works well. But,
> when I power off the cpu, and wake up and excute resume code, the kernel
> seem ok, but the busybox toolkit does not work proper, eg: "ls" can not
> output the result through serial port. i add "printk statement" trying to
> locate the reason, but at this time, the "ls" work fine.  hence, i doubt
> something must be corrupted after resume.
>  I have checked all the state register and co-processor, having not found
> any exception, and I also compared all the dram data before power off and
> after wake up, nothing have changed. Right now, I do not know what has
> happened, and what should I do to locate the real problem to make the
> busybox works ok. I also want to know does the linux kernel 3.0.8 support
> "suspend to ram" like this:
> "echo mem > /sys/power/state"  -> enter_state -> suspend_devices_and_enter
> ->suspend_ops->enter(state)?
> Can anyone give me some suggestion? Any comment is welcome, thanks a lot.
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