Bug 6071 - uhci_hcd and ohci_hcd prevents CPU from entering C3 state
Summary: uhci_hcd and ohci_hcd prevents CPU from entering C3 state
Alias: None
Product: Drivers
Classification: Unclassified
Component: USB (show other bugs)
Hardware: i386 Linux
: P2 normal
Assignee: Greg Kroah-Hartman
Depends on:
Blocks: USB
  Show dependency tree
Reported: 2006-02-14 11:09 UTC by Jakub Jozwicki
Modified: 2009-07-28 16:46 UTC (History)
2 users (show)

See Also:
Kernel Version: 2.6.25
Tree: Mainline
Regression: No

dmesg (33.44 KB, text/plain)
2006-02-15 05:22 UTC, Jakub Jozwicki
lspci -vvv (14.25 KB, text/plain)
2006-02-15 05:26 UTC, Jakub Jozwicki
lsusb -vvv (12.66 KB, text/plain)
2006-02-15 05:29 UTC, Jakub Jozwicki

Description Jakub Jozwicki 2006-02-14 11:09:56 UTC
Most recent kernel where this bug did not occur:  
Distribution: Gentoo  
Hardware Environment: AMD Turion 64, ASUS A6K laptop  
Software Environment:  
Problem Description: uhci_hcd and ohci_hcd prevents CPU from entering C3 state 
cat /proc/acpi/processor/CPU1/power: 
active state:            C2 
max_cstate:              C8 
bus master activity:     00200803 
    C1:                  type[C1] promotion[C2] demotion[--] latency[000] 
   *C2:                  type[C2] promotion[C3] demotion[C1] latency[099] 
    C3:                  type[C3] promotion[--] demotion[C2] latency[990] 
after rmmod ohci_hcd: 
active state:            C3 
max_cstate:              C8 
bus master activity:     00200800 
    C1:                  type[C1] promotion[C2] demotion[--] latency[000] 
    C2:                  type[C2] promotion[C3] demotion[C1] latency[099] 
   *C3:                  type[C3] promotion[--] demotion[C2] latency[990] 
Steps to reproduce: 
1) Buy some hardware with CPU supporting C3 power state and USB 1.1, USB mouse 
2) Install linux with coldplug/hotplug which will load drivers for mouse 
3) See that CPU never enters C3 and laptop life on battery is shortened 
by 30 minutes - 1 hour
Comment 1 Greg Kroah-Hartman 2006-02-14 16:38:32 UTC
Has this ever worked on other kernel version?

Can you enable CONFIG_USB_DEBUG and provide some debug log messages for
when you try to suspend?

Comment 2 Jakub Jozwicki 2006-02-15 05:22:48 UTC
Created attachment 7339 [details]
Comment 3 Jakub Jozwicki 2006-02-15 05:26:10 UTC
Created attachment 7342 [details]
lspci -vvv
Comment 4 Jakub Jozwicki 2006-02-15 05:29:45 UTC
Created attachment 7343 [details]
lsusb -vvv
Comment 5 Jakub Jozwicki 2006-02-15 05:44:25 UTC
> Has this ever worked on other kernel version? 
Probably not. 
Here is explanation of the problem: 
"When a USB device is attached to a PC, the USB host controller polls the frame  
scheduler in memory. This is a direct memory access (DMA) bus master operation.  
Any bus master traffic, interrupt, or one of several other system activities  
are "break events" that will move a CPU out of C3 because, by definition, the  
CPU's cache cannot be snooped while in C3. The resolution is selective suspend. 
This feature allows a driver to suspend the USB device it controls when the 
device becomes idle, even while the system itself remains in a fully 
operational power state (S0)." 
Comment 7 Greg Kroah-Hartman 2006-03-06 10:33:00 UTC
Yeah, this is a known issue with USB and Linux right now.  People
are working on it, but it will be a while before it's fixed.

I recommend just unloading the modules for now if you wish to suspend
and have good battery life.
Comment 8 Björn Jacke 2007-02-01 01:42:01 UTC
who is actually working on this? The bug should be assigned to them instead of
being "rejected documented". The ehci-hcd driver without polling works nice and
leaves the cpu in c3 state. uhci's polling is really a bad thing for some laptop
Comment 9 Natalie Protasevich 2008-03-18 02:34:51 UTC
Any update on this problem? Bjorn, have you tested with recent kernel?
Comment 10 HJH 2008-04-21 16:22:33 UTC
An update:
on kernel 2.6.25 this problem still exists!
Unloading the module does indeed make entering the C3 state possible, but it would  be nice to actually get this fixed (as by removing the module I also shut down the bluetooth and fingerprint scanner in the X61).
Comment 11 Greg Kroah-Hartman 2009-07-28 16:46:28 UTC
This is a hardware issue.  Will close as WILL_NOT_FIX unless someone submits some patches to implement this.

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