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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
B-device should take host role and enumrate A-device.
4) A-device switch back to host.
On A-device:
echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_req
or, 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"
1.4 OTG compliance test
Only below 3 popular gadget drivers are declared to be USB OTG and EH 2.0
compliant(with otg descriptor comply with USB OTG and EH 2.0 as a peripheral):
- mass storage
- ether
- serial