Hi Mathias, Thanks for the tip. It's really helpful. root@tegra-ubuntu:/d/usb/xhci/3610000.usb/ports/port04# cat portsc Powered Connected Enabled Link:U2 PortSpeed:4 Change: Wake: -JC On 2/26/20 5:32 PM, Mathias Nyman wrote: > On 26.2.2020 10.12, JC Kuo wrote: >> Hi Thierry, >> Yes, it can be verified with a LPM capable device. For example, a VIA USB 3.0 >> hub is connected to Jetson-Xavier. "lsusb -v" output [1] shows the device >> supports LPM and the host has enabled U1/U2 states for the device. If host LPM >> is disabled, there will be no "U1 Enabled" and "U2 Enabled" strings in "Device >> Status" section. >> >> To check LPM operation, disconnect all USB 3.0 devices from the hub and disable >> runtime PM for the super-speed portion of the hub, so that it won't be >> auto-suspended. >> root@tegra-ubuntu:~# echo on > /sys/bus/usb/devices/2-4/power/control >> >> Since there is no data transaction for the hub, link will enter U2 soon. This >> can be checked by reading XHCI.PORTSC register. In below, PLS (Port Link State) >> field is U2. >> root@tegra-ubuntu:~# devmem 0x3610450 >> 0x00001243 > > A more human friendly way to read portsc registers: > > # cat /sys/kernel/debug/usb/xhci/0000\:00\:14.0/ports/port02/portsc > Powered Connected Enabled Link:U0 PortSpeed:3 Change: Wake: > > -Mathias >
