On 10/15/07, David Brownell <david-b@xxxxxxxxxxx> wrote: > > From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx> > > Date: Mon, 15 Oct 2007 18:03:59 +0200 > > > > On Mon, 2007-10-15 at 14:43 +0200, Francis Moreau wrote: > > > > > So my question is that when we suspend the system, it seems that all > > > IRQs are masked and I'm a bit suprise since the event that should wake > > > up the system is an interrupt. This mask is done by > > > arch_suspend_disable_irqs() and none of the arch is overriding this > > > stub. If I'm right, how the system should be waked up ? > > > > No, well, in most cases the CPU is actually turned off by some other > > chip (like the PMU on powermac systems) and turned on again by it when > > the system should wake up. > > Not true on most embedded systems using ARM SOCs I've seen ... most > of those have the SOC enter a low power state which doesn't power off > the SOC, and moreover leaves the CPU (and most peripherals) in a low > power data-retaining state. > And it's my case too. > Coming back from suspend states (like "standby" or "suspend-to-RAM") > then doesn't involve any kind of powerup/reset at all. That's a goal, > since it shrinks the suspend/resume cycle time substantially. > True, and once the cpu is in standy mode, it's definitely not the thing which consumes power. > In conjunction with that model, the last step of entering a system > suspend state should involve disabling all IRQs that aren't flagged as > wakeup sources by enable_irq_wake(). Ok, I missed that because I'm using a 2.6.17 kernel. > That's shortly before the magic > which powers down memory and CPU, but after devices have all been told > to suspend themselves. > Is it done in pm_ops->enter method ? > > Of course, the CPU itself is often only a small part of the system's > power usage. More power is saved by powering devices down, or even > off. I'm thinking of making powering the disk off because when suspended it still uses more that 5W ! > In that example of a disk drive, one way to handle that would > be to introduce a power domain within which the drive's controller > and the drive both live. If that's properly located in the driver > model tree, as a device node, then its suspend and resume methods > could poer the drive off and on (respectively). > Do you have any examples that you could give ? BTW I'm using a SATA hard drive. Thanks -- Francis _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
