On Thu, Jul 19, 2012 at 11:42:57AM +0200, Oliver Neukum wrote: > On Thursday 19 July 2012 15:42:37 Lan Tianyu wrote: > > On 2012年07月19日 14:37, Oliver Neukum wrote: > > > > But this leaves me with a question. Has anybody ever measured the additional > > > power savings compared to a suspended state for devices? Or are you doing > > > this only as a prelude to become able to send host controllers to D3cold? > > hi Oliver: > > I have done a test on a usb3.0 ORICO SSD which may cost 3w normally. > > Traditional suspend can save 1w. Power off can save additional 2w. I also test > > 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. 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. Sarah Sharp -- 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
