USB OTG Serial on i.MX6 Android kk4.4.3_2.0.0

[mukelarvin]

Hi, I'm having some trouble getting the USB OTG port to appear as a usb serial port when connected to a PC.

- I.MX6DL custom board based on the SabreSD

- Android kk4.4.3_2.0.0 bsp

- USB OTG works for ADB with CONFIG_USB_G_ANDROID=y in my kernel config.

My understanding is that removing CONFIG_USB_G_ANDROID and setting CONFIG_USB_G_SERIAL=y should enable the serial mode. The device /dev/ttyGS0 appears in my device's file system but no computer sees the device when I plug in the usb otg port. What else should I be doing?

Device Tree Settings

Regulator

reg_usb_otg_vbus: usb_otg_vbus {
        compatible = "regulator-fixed";
        regulator-name = "usb_otg_vbus";
        regulator-min-microvolt = <5000000>;
        regulator-max-microvolt = <5000000>;
        gpio = <&gpio3 22 0>;
        enable-active-high;
};

USB OTG

&usbotg {
        vbus-supply = <&reg_usb_otg_vbus>;
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_usbotg_2>;
        disable-over-current;
        status = "okay";
};

[alejandrolozan1]

Hi,

Are you trying to configure the USB OTG port to work as a CDC device?

I just tried it out with L3.14.52 and it worked I just had to modprobe g_serial

Best Regards,

Alejandro

[mukelarvin]

Yeah I'd like it to be a CDC device. I'm trying to get the device to show up as a COM port on my windows PC.

I built the driver statically in the kernel and it appears to be getting loaded on boot:

root@sabresd_6dq:/ # ls -l /sys/module/g_serial
drwxr-xr-x root     root              1970-01-01 00:00 parameters
--w------- root     root         4096 1970-01-01 00:00 uevent

I think it is something to do with the USB port not being set up correctly. On my old 3.0.35 kernel I used to get messages for each USB port:

ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
fsl-ehci fsl-ehci.0: Freescale On-Chip EHCI Host Controller
fsl-ehci fsl-ehci.0: new USB bus registered, assigned bus number 1
fsl-ehci fsl-ehci.0: irq 75, io base 0x02184000
fsl-ehci fsl-ehci.0: USB 2.0 started, EHCI 1.00
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
add wake up source irq 72
fsl-ehci fsl-ehci.1: Freescale On-Chip EHCI Host Controller
fsl-ehci fsl-ehci.1: new USB bus registered, assigned bus number 2
fsl-ehci fsl-ehci.1: irq 72, io base 0x02184200
fsl-ehci fsl-ehci.1: USB 2.0 started, EHCI 1.00
hub 2-0:1.0: USB hub found
hub 2-0:1.0: 1 port detected

On the new kernel only one is initialized:

ci_hdrc ci_hdrc.1: doesn't support gadget
ci_hdrc ci_hdrc.1: EHCI Host Controller
ci_hdrc ci_hdrc.1: new USB bus registered, assigned bus number 1
ci_hdrc ci_hdrc.1: USB 2.0 started, EHCI 1.00
usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: EHCI Host Controller
usb usb1: Manufacturer: Linux 3.10.53-dirty ehci_hcd
usb usb1: SerialNumber: ci_hdrc.1
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected

Although it is weird that the Android ADB driver will still work with no mention of the port during the boot log. Any ideas?

[mukelarvin]

Here are the usb related items from the boot log:

usbcore: registered new interface driver asix
usbcore: registered new interface driver ax88179_178a
usbcore: registered new interface driver cdc_ether
usbcore: registered new interface driver net1080
usbcore: registered new interface driver cdc_subset
usbcore: registered new interface driver zaurus
usbcore: registered new interface driver cdc_ncm
ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
usbcore: registered new interface driver cdc_acm
cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
usbcore: registered new interface driver usb-storage
usbcore: registered new interface driver usbserial
usbcore: registered new interface driver option
usbserial: USB Serial support registered for GSM modem (1-port)
ci_hdrc ci_hdrc.1: doesn't support gadget
ci_hdrc ci_hdrc.1: EHCI Host Controller
ci_hdrc ci_hdrc.1: new USB bus registered, assigned bus number 1
ci_hdrc ci_hdrc.1: USB 2.0 started, EHCI 1.00
usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: EHCI Host Controller
usb usb1: Manufacturer: Linux 3.10.53-dirty ehci_hcd
usb usb1: SerialNumber: ci_hdrc.1
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
mousedev: PS/2 mouse device common for all mice
usbcore: registered new interface driver xpad
usbcore: registered new interface driver usb_acecad
usbcore: registered new interface driver aiptek
usbcore: registered new interface driver gtco
usbcore: registered new interface driver hanwang
usbcore: registered new interface driver kbtab
usbcore: registered new interface driver wacom
usbcore: registered new interface driver uvcvideo
USB Video Class driver (1.1.1)
...
hidraw: raw HID events driver (C) Jiri Kosina
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
...
usb_otg_vbus: disabling