2.6.{9,10}: C3 not working once USB driver gets loaded (ThinkPad T40p)

2.6.{9,10}: C3 not working once USB driver gets loaded (ThinkPad T40p)

[Tomas Szepe]

Hi,

In recent kernels (tried 2.6.9, 2.6.10), after I load the uhci_hcd module,
the processor never goes to state C3.  Unloading the module again puts things
back to normal.  The system is an IBM ThinkPad T40p.

Is the USB driver setting some kinda flag in the ACPI subsystem to achieve
this behavior intentionally or is this a bug?

Thanks,
-- 
Tomas Szepe <szepe@pinerecords.com>

Re: 2.6.{9,10}: C3 not working once USB driver gets loaded (ThinkPad T40p)

[Len Brown]

On Sun, 2004-12-26 at 15:50, Tomas Szepe wrote:
> Hi,
> 
> In recent kernels (tried 2.6.9, 2.6.10), after I load the uhci_hcd
> module, the processor never goes to state C3.  Unloading the module
> again puts things back to normal.  The system is an IBM ThinkPad T40p.
> 
> Is the USB driver setting some kinda flag in the ACPI subsystem to
> achieve this behavior intentionally or is this a bug?

It is not a Linux bug -- it is a system hardware architecture flaw.

There is a workaround for this issue called
USB Selective Suspend, which you can google and
read all about.  Hopefully we'll have this workaround
available on Linux systems before too long.

cheers,
-Len