On Tue, 2011-09-06 at 08:27 -0700, Greg KH wrote: > On Tue, Sep 06, 2011 at 03:51:47PM +0800, Andiry Xu wrote: > > This patch adds sysfs support to xHCI usb2 hardware LPM, so user can enable > > and disable usb2 hardware LPM manually. > > > > Signed-off-by: Andiry Xu <andiry.xu@xxxxxxx> > > --- > > Documentation/usb/power-management.txt | 29 ++++++++++++++++ > > drivers/usb/core/sysfs.c | 56 ++++++++++++++++++++++++++++++++ > > 2 files changed, 85 insertions(+), 0 deletions(-) > > > > diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt > > index c9ffa9c..9e5d9dd 100644 > > --- a/Documentation/usb/power-management.txt > > +++ b/Documentation/usb/power-management.txt > > @@ -487,3 +487,32 @@ succeed, it may still remain active and thus cause the system to > > resume as soon as the system suspend is complete. Or the remote > > wakeup may fail and get lost. Which outcome occurs depends on timing > > and on the hardware and firmware design. > > + > > + > > + xHCI hardware link PM > > + --------------------- > > + > > +xHCI host controller provides hardware link power management to usb2.0 > > +(xHCI 1.0 feature) and usb3.0 devices which support link PM. By > > +enabling hardware LPM, the host can automatically put the device into > > +lower power state(L1 for usb2.0 devices, or U1/U2 for usb3.0 devices), > > +which state device can enter and resume very quickly. > > + > > +The user interface for controlling USB2 hardware LPM is located in the > > +power/ subdirectory of each USB device's sysfs directory, that is, in > > +/sys/bus/usb/devices/.../power/ where "..." is the device's ID. The > > +relevant attribute files is usb2_hardware_lpm. > > + > > + power/usb2_hardware_lpm > > This also needs to go into Documentation/ABI/ right? > Yes, I assume it should be added to Testing directory. > > + When a USB2 device which support LPM is plugged to a > > + xHCI host root hub which support software LPM, the > > + host will run a software LPM test for it; if the device > > + enters L1 state and resume successfully and the host > > + supports USB2 hardware LPM, it will enable hardware LPM > > + for the device and the file shows "enable", otherwise > > + it shows "disable". You can write those words to the > > + file to enable/disable USB2 hardware LPM manually only > > + if the device can perform LPM and the host supports > > + hardware LPM. When driver suspend the port into U3 > > + state, it will disable hardware LPM first. > > This file should only show up if the device supports this, not for all > devices like this patch has. > Okay, will do that. > And why would you not enable this for a device that supports this? > The current test result of software LPM is not very optimistic: many devices claim to support LPM but fail to do so, and although the device I have passed LPM test work properly on the host with hardware LPM enabled, I'm not sure how other devices and hosts will behave. Add a switch in sysfs help debugging in some cases. Thanks, Andiry -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
