HelenOS sources

XHCI_PORT_PLC     121 uspace/drv/bus/usb/xhci/debug.c 	DUMP_REG(port, XHCI_PORT_PLC);
XHCI_PORT_PLC      61 uspace/drv/bus/usb/xhci/rh.c     XHCI_REG_MASK(XHCI_PORT_PLC) |
HelenOS homepage, sources at GitHub