(cc'ing Len) Hi Mark, On Mon, 11 Jul 2011, Mark Brown wrote: > The interesting bits are things like being able to kill lots of the SoC > core supplies when the RAM is in retention mode - the CPU needs to go > through its shutdown procedures. This is indeed possible on OMAP3+ chips with TWL4030+ PMICs. Probably other PMICs also. TI calls it "off-mode." The N900 shipped with this feature enabled. Not sure how many other similar products did. This can be enabled in mainline, but not all of the mainline drivers have context save/restore code merged yet, so in mainline it only works with a subset of drivers. > Actually, it just occurred to me that if we're waiting for a system > timer and can hand that off to a suitable timer in the PMIC then we can > do a suspend to RAM for the deep idle state from the hardware point of > view. Yep. At LinuxCon Cambridge two years ago, we had a discussion about whether it would be possible to enter ACPI S-states from CPUIdle (or some idle governor) on Intel chips. If I remember correctly, the conclusion was that ACPI always disables the screen/backlight, so it would only be useful for situations where that was acceptable. To the best of my (limited) knowledge, that's the only case I know of where there's a hardware limitation that prevents dynamic idle from reaching the same low power state as system suspend. If someone has hard details of a similar example, it would be great to know about it. - Paul -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
