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? > + 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. And why would you not enable this for a device that supports this? greg k-h -- 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
