[Bugme-new] [Bug 12391] New: Processor does not go below C2 state until usb.autosuspend is enabled

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=12391

           Summary: Processor does not go below C2 state until
                    usb.autosuspend is enabled
           Product: Power Management
           Version: 2.5
     KernelVersion: 2.6.28
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Other
        AssignedTo: power-management_other at kernel-bugs.osdl.org
        ReportedBy: imrehg at gmail.com


Latest working kernel version:
2.6.27.10

Earliest failing kernel version:
2.6.28

Distribution:
Self-compiled kernel (on Arch Linux)

Hardware Environment:
Asus EeePC 8G, with replaced wireless card and increased memory


Software Environment:
-

Problem Description:
In the 2.6.27.10 kernel right after boot, if the CPU was idle, it went down to
the C3 state (according to PowerTop 1.11). Powertop recommends usb.autosuspend
to be enabled, but that does not change the processor's state.
In the 2.6.28 kernel, after boot the processor is stuck in C2 state. Powertop
recommends usb.autosuspend, then the processor goes down successfully to C3
state.

Steps to reproduce:
1) Boot with 2.6.27.10 kernel
2) Use powertop to see C-state statistics (~100% in C3)
3) Boot with 2.6.28 kernel
4) Use powertop to see C-state statistics (~100% in C2)
5) Enable usb.autosuspend from powertop (~100% in C3)


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