DESK-MX8M-L/Peripherals/USB2 OTG

History
ID#	Issue Date	Notes
15718	30/12/2021	First DESK-MX8M-L release
17615	24/02/2023	DESK-MX8M-L-2.0.0 release
17615	26/07/2023	DESK-MX8M-L-4.0.0 release

Peripheral USB2 OTG

Device tree configuration

ORCA SOM

Here below an example of device tree configuration used on standard DAVE's kit for the ORCA SOM:

From imx8mp-mito8mplus-cb1001.dts:

...
...
&usb3_phy1 {
	fsl,phy-tx-preemp-amp-tune = <2>;
	status = "okay";
};

&usb3_1 {
	status = "okay";
};

&usb_dwc3_1 {
	dr_mode = "otg";
	extcon = <&extcon_usbotg2>;
	hnp-disable;
	srp-disable;
	adp-disable;
	rsp-disable;
	disable-over-current;
	status = "okay";
};
...
...

MITO 8M Mini

Here below an example of device tree configuration used on standard DAVE's kit for the MITO 8M Mini:

From imx8mm-mito8mmini.dts:

...
...
&usbotg2 {
	dr_mode = "host";
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_usb_pwr>;
	vbus-supply = <&reg_usb_pwr>;
	picophy,pre-emp-curr-control = <3>;
	picophy,dc-vol-level-adjust = <7>;
	status = "okay";
};
...
...
&iomuxc {
...
...
	pinctrl_usb_pwr: usbpwrgrp {
		fsl,pins = <
			MX8MM_IOMUXC_GPIO1_IO12_GPIO1_IO12			  0x19
		>;
	};
...
...
};

Accessing the peripheral SBC ORCA

Linux messages in host mode

When a USB 2.0 peripheral is inserted, in the following example a memory mass storage device, the kernel recognizes the device (i.e. class, vendor id, product id, etc.)

root@desk-mx8mp:~# [  949.406404] [ 6491.481175] usb 3-1: new high-speed USB device number 3 using xhci-hcd
[ 6491.639810] usb-storage 3-1:1.0: USB Mass Storage device detected                     
[ 6491.646905] scsi host0: usb-storage 3-1:1.0                                                                         
[ 6493.775259] scsi 0:0:0:0: Direct-Access     Fanxiang F206             1100 PQ: 0 ANSI: 4
[ 6493.786654] sd 0:0:0:0: [sda] 61440000 512-byte logical blocks: (31.5 GB/29.3 GiB)                       
[ 6493.795475] sd 0:0:0:0: [sda] Write Protect is off                                                                  
[ 6493.801799] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 6493.818546]  sda: sda1                                                                                              
[ 6493.824653] sd 0:0:0:0: [sda] Attached SCSI removable disk
root@desk-mx8mp:~#

When a USB 3.0 peripheral is inserted, in the following example a memory mass storage device, the kernel recognizes the device (i.e. class, vendor id, product id, etc.)

root@desk-mx8mp:~# [ 6798.669673] usb 4-1: new SuperSpeed USB device number 3 using xhci-hcd
[ 6798.703673] usb-storage 4-1:1.0: USB Mass Storage device detected
[ 6798.710479] scsi host1: usb-storage 4-1:1.0
[ 6799.719808] scsi 1:0:0:0: Direct-Access     Wilk     USB DISK 3.0     PMAP PQ: 0 ANSI: 6
[ 6799.732902] sd 1:0:0:0: [sdb] 60628992 512-byte logical blocks: (31.0 GB/28.9 GiB)
[ 6799.741747] sd 1:0:0:0: [sdb] Write Protect is off
[ 6799.747177] sd 1:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[ 6799.934800]  sdb:
[ 6799.940848] sd 1:0:0:0: [sdb] Attached SCSI removable disk

Usage in device mode with mass-storage

root@desk-mx8mp:~#  dd if=/dev/zero of=mass_storage count=256 bs=1M
256+0 records in                                                                                                       
256+0 records out   
268435456 bytes (268 MB, 256 MiB) copied, 0.987911 s, 272 MB/s
root@desk-mx8mp:~# mkfs.msdos mass_storage                                                                                                                                                                                                    
mkfs.fat 4.2 (2021-01-31)
root@desk-mx8mp:~# mkdir loop
root@desk-mx8mp:~# mount -o loop mass_storage loop
[ 6664.248804] loop0: detected capacity change from 0 to 524288
root@desk-mx8mp:~# echo "Test USB OTG with mass storage device" > loop/usb.txt
root@desk-mx8mp:~# umount loop
root@desk-mx8mp:~# 

then insert the g_mass_storage kernel module driver enabling an Windows PC to see it as a removable device

root@desk-mx8mp:~# modprobe g_mass_storage removable=y file=mass_storage
[ 6677.844877] Mass Storage Function, version: 2009/09/11
[ 6677.850190] LUN: removable file: (no medium)
[ 6677.854585] LUN: removable file: /home/root/mass_storage
[ 6677.859933] Number of LUNs=1
[ 6677.863239] g_mass_storage gadget: Mass Storage Gadget, version: 2009/09/11
[ 6677.870221] g_mass_storage gadget: userspace failed to provide iSerialNumber
[ 6677.877281] g_mass_storage gadget: g_mass_storage ready
root@desk-mx8mp:~#

Once the USB cable is connected to the PC, the kernel prints the following messages:

root@desk-mx8mp:~# [ 1493.477167] g_mass_storage gadget: high-speed config #1: Linux File-Backed Storage

and the Windows PC activate the driver and the disk is available as a Drive Unit (with the usb.txt file available).

Accessing the peripheral MITO 8M Mini

Linux messages

When a USB 2.0 peripheral is inserted, in the following example a memory mass storage device, the kernel recognizes the device (i.e. class, vendor id, product id, etc.)

root@desk-mx8mm:~# [   22.858909] usb 1-1: new high-speed USB device number 2 using ci_hdrc
[   23.022240] usb-storage 1-1:1.0: USB Mass Storage device detected
[   23.028819] scsi host0: usb-storage 1-1:1.0
[   24.045317] scsi 0:0:0:0: Direct-Access     SanDisk  Cruzer Force     1.00 PQ: 0 ANSI: 6
[   24.055280] sd 0:0:0:0: [sda] 60088320 512-byte logical blocks: (30.8 GB/28.7 GiB)
[   24.063993] sd 0:0:0:0: [sda] Write Protect is off
[   24.069617] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[   24.142194]  sda: sda1
[   24.150358] sd 0:0:0:0: [sda] Attached SCSI removable disk

Additional information in host mode

If the root file system configuration does not automatically mount the partition, it is possible to mount the device using the following command:

root@desk-mx8mp:~# mkdir -p /mnt/usb
root@desk-mx8mp:~# mount /dev/sda1 /mnt/usb
[ 1245.415662] FAT-fs (sda1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
root@desk-mx8mp:~# ls -la /mnt/usb
total 128
drwxr-xr-x 10 root root  4096 Jan  1  1970 .
drwxr-xr-x  3 root root  4096 Dec 30 11:24 ..
drwxr-xr-x  2 root root  4096 May 13  2021 System Volume Information
drwxr-xr-x  2 root root  4096 Nov 17 15:27 boot
-rwxr-xr-x  1 root root  8016 Nov 17 15:27 boot.scr
-rwxr-xr-x  1 root root  1712 Dec 10 16:16 config.txt
drwxr-xr-x  2 root root  4096 Nov 17 15:27 rfs
-rwxr-xr-x  1 root root 57458 Nov 17 15:27 run-system-update.sh
-rwxr-xr-x  1 root root   531 Nov 17 15:27 settings.txt

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