On Tue, 25 Nov 2014, tianjulin wrote: > Hi Stern, > > *1*:I turn off media-change polling when connect sdcard-reader,the usb > bus still can't enter runtime suspend.I guss sdcard-reader can't enter > runtime suspend cause the usb bus cat't enter runtime suspend,but I > can't understand that why the sdcard-reader can't enter runtime suspend > if have no Operating.
Because you have to enable runtime suspend. It is turned off by default. > *2*: connect USB storage,the run command as A->B->C->D,the usb bus still > can't enter runtime suspend. > *A：* > shell@byt_t_crv2:/sys/bus/usb/devices # ls > 1-0:1.0 > 1-2 > *1-2:1.0* > 2-0:1.0 > usb1 > usb2 > shell@byt_t_crv2:/sys/bus/usb/devices # > *B：* > shell@byt_t_crv2:/sys/bus/usb/devices/1-2:1.0/power # ls > shell@byt_t_crv2:/sys/bus/usb/devices/1-2:1.0/power # > have any files show. > > *C：* > shell@byt_t_crv2:/sys/bus/usb/devices/1-2/power # ls > active_duration > autosuspend > autosuspend_delay_ms > connected_duration > control > level > persist > runtime_active_time > runtime_status > runtime_suspended_time > shell@byt_t_crv2:/sys/bus/usb/devices/1-2/power # > > *D：* > shell@byt_t_crv2:#echo auto > /sys/bus/usb/devices/1-2/power/control > > > *3:*The bus won't enter runtime suspend until all of the devices attached > to the bus are in runtime suspend > ---------------why I have no any operation,connect usb and run "echo auto > > control",the usb bus still can't runtime suspend? why usb storage can't enter > runtime suspend if have no any operation? What you did isn't enough. You also need to enable runtime suspend for the card reader's sd device. For example, echo 1000 >/sys/bus/usb/devices/1-2:1.0/host2/target2:0:0/2:0:0:0/power/autosuspend_delay_ms echo auto >/sys/bus/usb/devices/1-2:1.0/host2/target2:0:0/2:0:0:0/power/control Some of those path names may be different on your system. Basically, you need to visit every "power" directory under /sys/bus/usb/devices/1-2, and make sure they contain "auto" in power/control and a reasonable value in power/autosuspend_delay_ms. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
