Messages in this thread |  | | Subject | RE: ACPI C and P states on Conroe | Date | Tue, 30 Jan 2007 14:31:14 -0800 | From | "Pallipadi, Venkatesh" <> |
| |
C0 is the state when processor is executing instruction. C1-C3 is the state that kernel puts the CPU into when there is nothing to run (idle loop). C1 is supported by all processors and it is entered either by using "hlt" or "mwait" instructions. You don't have to do anything to enable this. It should be getting used already (unless you are using "idle=poll" in which case C1 will not be used). C2 and C3 however are not supported on all processors/platforms typically. If it is supported, BIOS will export these states information to OS, through ACPI and kernel acpi processor module will enable those states. As long as you have CONFIG_ACPI_PROCESSOR enabled, this support will be built in and should get enabled (if your platform supports this feature). There are no magic setup to enable this. If present, you will see info about these C-states here - /proc/acpi/processor/CPU*/power
-Venki
>-----Original Message----- >From: linux-kernel-owner@vger.kernel.org >[mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Joe Harvell >Sent: Tuesday, January 30, 2007 9:34 AM >To: linux-kernel@vger.kernel.org >Subject: ACPI C and P states on Conroe > >I am trying to enable all the power saving features I can on my Conroe >E6600. After much searching on the web, I am a little confused about >the Linux kernel support for ACPI on the Conroe. > >Here is my setup: >Intel Core2 Duo E6600 >Asus P5-B Deluxe board (Intel P965). >I am running a Gentoo kernel based on 2.6.19.4. > >I have managed to enable EIST using cpufreq with the >speedstep-centrino >driver. But my understanding from browsing the ACPI spec is that this >is still within C0, i.e. not much power savings. > >Here are my questions: > >1) For P states, which cpufreq driver should I be using? I've heard >speedstep-centrino is deprecated (but only some aspects of it) >that are >being moved into acpi-cpufreq. But I can't get acpi-cpufreq >to load in >my kernel version. Also, I would have thought speedstep-ich would be >the driver, just based on the name. How do I know (other than trying >all modules to see which one loads) which one I should be using? >2) What kind of support for C1-C3 does the Conroe have? The ACPI spec >says C2 and C3 require chipset support on the motherboard. Does P965 >have that. Does it matter between boards (e.g. P5B)? >3) What versions of the kernel support C1-C3 states? What kernel >options are germane to this? What libraries/tools are involved? > >--- >Joe Harvell >- >To unsubscribe from this list: send the line "unsubscribe >linux-kernel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html >Please read the FAQ at http://www.tux.org/lkml/ > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |