On Mon, 5 Jan 2015, vichy wrote: > hi all: > after tracing and reading kernel usb source code about run time and > normal suspend. > 1. how could we check the rum time suspend is work on some device? > By plugging in devices and check whether > /sys/bus/usb/devices/.../power/ is empty or not? No. That directory will never be empty. You can check whether runtime suspend works by enabling it: echo auto >/sys/bus/usb/devices/.../power/control You can see whether the device has been suspended by looking at the runtime_status and runtime_suspended_time files in the .../power directory. > 2. I plug in one mouse and found the device will auto disconnect every > 2 secs, the default value of usb_autosuspend_delay. > But I have some questions > a. how kernel judge the device is idle, from usb spec, the idle > mean there is no any bus traffic, including sof, over 3ms and host > will always firing sof even there is no transaction on the bus. The kernel judges a device to be idle if it hasn't been used in some time. The bus traffic has nothing to do with it. > b. I think dynamic suspend is used for saving power when device is > idle for a specific time, but why the mouse will dynamic resume when > suspend for a while. it should resume when user or external event > trigger it for resume right? That's right. If your mouse is resuming, it must be because some event has triggered the resume. 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
