On Sun, 29 Jun 2008, garkein@xxxxxxxxxxxxxxxx wrote: > Hello, > with recent powertop, I could confirm that my T61 uses the C6 processor > state only in battery mode: > > (Kernel 2.6.25) > > AC: > Your CPU supports the following C-states : C1 C2 C3 C4 C5 C6 > Your BIOS reports the following C-states : C1 C2 C3 > > Battery: > Your CPU supports the following C-states : C1 C2 C3 C4 C5 C6 > Your BIOS reports the following C-states : C1 C2 C6 > > Since the notebook runs quite a bit cooler, and thus less noisy (fan) in > battery mode, I would like to have it use that C6 state also in AC mode. > Is it possible, maybe with some slight tweaks, to convice the kernel (or > BIOS?) to also use that C6 state when in AC mode? Lenovo decided when they designed the platform to do extra work to switch what ACPI C3 means on AC vs DC. They chose to have lower latency on AC, and save energy on DC. (you will notice lower latency reported for C3 when on DC if you look in /proc/acpi/processor/*/power or in /sys/devices/system/cpu/cpu*/cpuidle/*/latency eg. it may switch between 57usec and 17usec if you boot with "processor.nocst=1" then you'll use the legach FADT method of specifying C-states, and will lose the AC/DC switching capability, and also lose the MWAIT capability -- though you'll unlikely notice. So you'll get stuck with a single C3 state -- dunno if it is the one you prefer or the one you don't prefer... If this doesn't help and you want to hack your driver, then just go to acpi_processor_notify() in processor_core.c and disable the call to acpi_processor_cst_has_changed() and boot on DC... The long term answer to your question is that we are hoping to get permission to ship a native intel_idle driver which will give Linux the option to ignore the ACPI BIOS in this area. cheers, -Len -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
