On Thu, 12 Jul 2007, Rafael J. Wysocki wrote:
note that what devices get put to sleep could be configurable, potentially
to the extreme of things like the OLPC (that have hardware designed for
cheap sleeping) going into a light suspend-to-ram state between keystrokes
if nothing else has a timer event scheduled before that.
Suspend-do-disk (Hibernate) involves stopping the system, makeing a
snapshot of ram, writing the snapshot to somewhere and powering off the
box. on wakeup (power-on) a helper kernel boots, loads the snapshot into
ram and jumps to the kernel in the snapshot to resume operation.
as I understand the proposal the thought is to do the following
1. system kernel does suspend-to-ram to put the devices into a known safe
state.
Not necessarily suspend-to-RAM. I'd much prefer it if devices were not put
into low power states but quiesced (ie. no DMA, no interrupts).
as I asked in another message, is it really worth having two (or more)
modes here?
I think so. The suspend-to-RAM mode is quite specific and on some platform
(ie. ACPI) it requires platform support.
We've already reached the conclusion that it's better to separate suspend from
hibernation, as far as device drivers are concerned, and let's not repeat the
discussion.
Ok, I seem to have been miscommunicating here. the old combined
suspend/hibernate took everything to the hibernate state even if you only
needed to suspend.
I was still seeing two diffent states involved
for suspend go to low-power mode
for hibernate go to low-power mode, kexec the new kernel, do your stuff, power off
note that this doesn't really matter as you have pointed out in other
messages that we don't really want to put things in low-power mode, and
Eric pointed out that kexec already handles disabling devices, so it
sounds like this may be a solved problem if he's right and an issue to be
solved differently if he's not.
David Lang
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