Am Mittwoch, den 18.03.2009, 14:08 -0400 schrieb Len Brown: > 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 Thank you Len for your explanation. The long term way would be my preference as I don't want to be "stuck" with a single state. (I want them all! ;-)). Regards, Daniel -- 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
