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+1. How to test OTG FSM(HNP and SRP)
+-----------------------------------
+To show how to demo OTG HNP and SRP functions via sys input files
+with 2 Freescale i.MX6Q sabre SD boards.
+
+1.1 How to enable OTG FSM in menuconfig
+---------------------------------------
+Select CONFIG_USB_OTG_FSM, rebuild kernel Image and modules.
+If you want to check some internal variables for otg fsm,
+select CONFIG_USB_CHIPIDEA_DEBUG, there are 2 files which
+can show otg fsm variables and some controller registers value:
+cat /sys/kernel/debug/ci_hdrc.0/otg
+cat /sys/kernel/debug/ci_hdrc.0/registers
+
+1.2 Test operations
+-------------------
+1) Power up 2 Freescale i.MX6Q sabre SD boards with gadget class driver loaded
+   (e.g. g_mass_storage).
+
+2) Connect 2 boards with usb cable with one end is micro A plug, the other end
+   is micro B plug.
+
+   The A-device(with micro A plug inserted) should enumrate B-device.
+
+3) Role switch
+   On B-device:
+   echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
+
+   if HNP polling is not supported, also need:
+   On A-device:
+   echo 0 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_req
+
+   B-device should take host role and enumrate A-device.
+
+4) A-device switch back to host.
+   On B-device:
+   echo 0 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
+
+   A-device should switch back to host and enumrate B-device.
+
+5) Remove B-device(unplug micro B plug) and insert again in 10 seconds,
+   A-device should enumrate B-device again.
+
+6) Remove B-device(unplug micro B plug) and insert again after 10 seconds,
+   A-device should NOT enumrate B-device.
+
+   if A-device wants to use bus:
+   On A-device:
+   echo 0 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_drop
+   echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_req
+
+   if B-device wants to use bus:
+   On B-device:
+   echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
+
+7) A-device power down the bus.
+   On A-device:
+   echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_drop
+
+   A-device should disconnect with B-device and power down the bus.
+
+8) B-device does data pulse for SRP.
+   On B-device:
+   echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
+
+   A-device should resume usb bus and enumrate B-device.
+
+1.3 Reference document
+----------------------
+"On-The-Go and Embedded Host Supplement to the USB Revision 2.0 Specification
+July 27, 2012 Revision 2.0 version 1.1a"