On Fri, 20 Jul 2012, Sarah Sharp wrote: > > Well, then the device violates the standard for power consumption. > > Not necessarily. > > Tianyu, are you measuring the whole system power consumption or just the > power drawn by the device? How are you measuring power consumption? > > Also, are you sure the mass storage device was actually suspended? > Unfortunately, userspace polls unmounted drives every two seconds or so > to see if there's a medium change. So even though you may have enabled > auto-suspend, userspace will still be waking the device out of suspend > every two seconds. That might explain your high suspend power > consumption. > > You would need to unload the mass storage driver to truly measure > uninterrupted suspend power consumption. It is possible to disable this polling without unloading usb-storage: echo 0 >/sys/block/sdX/events_poll_msec > You can also set the power/autosuspend_delay_ms to something very low, > like 10, in order to get the mass storage device into suspend faster > than every two seconds. Alan Stern -- 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
