tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
11. How to test OTG FSM(HNP and SRP)
2-----------------------------------
3To show how to demo OTG HNP and SRP functions via sys input files
4with 2 Freescale i.MX6Q sabre SD boards.
5
61.1 How to enable OTG FSM in menuconfig
7---------------------------------------
8Select CONFIG_USB_OTG_FSM, rebuild kernel Image and modules.
9If you want to check some internal variables for otg fsm,
10mount debugfs, there are 2 files which can show otg fsm
11variables and some controller registers value:
12cat /sys/kernel/debug/ci_hdrc.0/otg
13cat /sys/kernel/debug/ci_hdrc.0/registers
14
151.2 Test operations
16-------------------
171) Power up 2 Freescale i.MX6Q sabre SD boards with gadget class driver loaded
18 (e.g. g_mass_storage).
19
202) Connect 2 boards with usb cable with one end is micro A plug, the other end
21 is micro B plug.
22
23 The A-device(with micro A plug inserted) should enumrate B-device.
24
253) Role switch
26 On B-device:
27 echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
28
29 B-device should take host role and enumrate A-device.
30
314) A-device switch back to host.
32 On B-device:
33 echo 0 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
34
35 or, by introducing HNP polling, B-Host can know when A-peripheral wish
36 to be host role, so this role switch also can be trigged in A-peripheral
37 side by answering the polling from B-Host, this can be done on A-device:
38 echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_req
39
40 A-device should switch back to host and enumrate B-device.
41
425) Remove B-device(unplug micro B plug) and insert again in 10 seconds,
43 A-device should enumrate B-device again.
44
456) Remove B-device(unplug micro B plug) and insert again after 10 seconds,
46 A-device should NOT enumrate B-device.
47
48 if A-device wants to use bus:
49 On A-device:
50 echo 0 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_drop
51 echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_req
52
53 if B-device wants to use bus:
54 On B-device:
55 echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
56
577) A-device power down the bus.
58 On A-device:
59 echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/a_bus_drop
60
61 A-device should disconnect with B-device and power down the bus.
62
638) B-device does data pulse for SRP.
64 On B-device:
65 echo 1 > /sys/bus/platform/devices/ci_hdrc.0/inputs/b_bus_req
66
67 A-device should resume usb bus and enumrate B-device.
68
691.3 Reference document
70----------------------
71"On-The-Go and Embedded Host Supplement to the USB Revision 2.0 Specification
72July 27, 2012 Revision 2.0 version 1.1a"
73
742. How to enable USB as system wakeup source
75-----------------------------------
76Below is the example for how to enable USB as system wakeup source
77at imx6 platform.
78
792.1 Enable core's wakeup
80echo enabled > /sys/bus/platform/devices/ci_hdrc.0/power/wakeup
812.2 Enable glue layer's wakeup
82echo enabled > /sys/bus/platform/devices/2184000.usb/power/wakeup
832.3 Enable PHY's wakeup (optional)
84echo enabled > /sys/bus/platform/devices/20c9000.usbphy/power/wakeup
852.4 Enable roothub's wakeup
86echo enabled > /sys/bus/usb/devices/usb1/power/wakeup
872.5 Enable related device's wakeup
88echo enabled > /sys/bus/usb/devices/1-1/power/wakeup
89
90If the system has only one usb port, and you want usb wakeup at this port, you
91can use below script to enable usb wakeup.
92for i in $(find /sys -name wakeup | grep usb);do echo enabled > $i;done;
93