[ltp] T400 does not enter C4/C6 sleep state with USB devices connected

Henrique de Moraes Holschuh linux-thinkpad@linux-thinkpad.org
Thu, 18 Feb 2010 16:36:51 -0200

On Thu, 18 Feb 2010, Pedro Ribeiro wrote:
> I spent lots of hours trying to figure out why my T400 would not enter
> C4 and C6 sleep states.
> Here are my findings for anyone which is interested:
> - When a USB device is connected, even if it supports USB autosuspend,
> the cpu will never go down more than C3 (apparently the mode is
> disabled by the BIOS).
> - After removing all the USB devices, in AC it enters C4 and in
> battery it enters C6.
> So one more reason not to use USB devices while on battery...

Did you try that using only EHCI (unload uhci_hcd) and USB2.0 devices?

  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh