Subject: [PATCH 2/5] ARM: PXA: Zipit Z2: Add USB host and device support

From: [email-masked] (Daniel Mack)
Date: Mon, 29 Oct 2012 12:14:34 +0100

On 29.10.2012 12:12, Vasily Khoruzhick wrote:
> On Mon, Oct 29, 2012 at 2:00 PM, Daniel Mack <[email-masked]> wrote:
> 
>>> Well, there's an issue - Z2 does not preserve memory contents in deep sleep
>>> (but it does in sleep), so userspace can't be fixed here unfortunatelly.
>>> There's no another possibility to turn Z2 off, and plain sleep is too
>>> power hungry.
>>> So the only way to keep Z2 in low-power mode is fake power off, which just puts
>>> Z2 in deep sleep.
>>
>> Why can't the userspace trigger a deep sleep then instead of powering
>> off? Which details do I lack?
> 
> How? echo mem >/sys/power/state puts system into non-deep sleep. Anyway, kernel
> is not ready for fake power off instead of suspend (we can't resume
> from deep sleep,
> memory content is not preserved), so there can be some data loss.
> Adding some sysfs file to control sleep type does not look like a good
> idea to me.
> 
> Btw, how other DT-capable boards handle power off?

No idea. I never actually used that kind of power state.