DESK-MX8M-L/Peripherals/USB1 OTG

History
ID#	Issue Date	Notes
15724	30/12/2021	First DESK-MX8M-L release
17612	24/02/2023	DESK-MX8M-L-2.0.0 release

Peripheral USB1 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_phy0 {
	vbus-power-supply = <&ptn5110>;
	fsl,phy-tx-vref-tune = <6>;
	fsl,phy-tx-rise-tune = <0>;
	fsl,phy-tx-preemp-amp-tune = <3>;
	fsl,phy-comp-dis-tune = <7>;
	fsl,pcs-tx-deemph-3p5db = <0x21>;
	fsl,phy-pcs-tx-swing-full = <0x7f>;
	status = "okay";
};

&usb3_0 {
	status = "okay";
};

&usb_dwc3_0 {
	dr_mode = "host";
	status = "okay";

	port {
		usb3_drd_sw: endpoint {
			remote-endpoint = <&typec_dr_sw>;
		};
	};
};
...
...

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:

...
...
&usbotg1 {
	dr_mode = "otg";
	picophy,pre-emp-curr-control = <3>;
	picophy,dc-vol-level-adjust = <7>;
	disable-over-current;
	srp-disable;
	hnp-disable;
	adp-disable;
	status = "okay";
};
...
...

Accessing the peripheral SBC ORCA

Linux messages in host mode

When a USB2.0 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:~# [  124.730657] usb 1-1.3: new high-speed USB device number 3 using xhci-hcd
[  124.858934] usb-storage 1-1.3:1.0: USB Mass Storage device detected
[  124.866497] scsi host0: usb-storage 1-1.3:1.0
[  125.881336] scsi 0:0:0:0: Direct-Access     SanDisk  Cruzer Force     1.00 PQ: 0 ANSI: 6
[  125.890902] sd 0:0:0:0: [sda] 60088320 512-byte logical blocks: (30.8 GB/28.7 GiB)
[  125.899491] sd 0:0:0:0: [sda] Write Protect is off
[  125.904560] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[  125.957498]  sda: sda1
[  125.967343] sd 0:0:0:0: [sda] Attached SCSI removable disk

When a USB3.0 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:~# [  214.438903] usb 2-1.1: new SuperSpeed Gen 1 USB device number 5 using xhci-hcd
[  214.464780] usb-storage 2-1.1:1.0: USB Mass Storage device detected
[  214.471655] scsi host1: usb-storage 2-1.1:1.0
[  215.503580] scsi 1:0:0:0: Direct-Access     HYPER    FLASHDISK        1507 PQ: 0 ANSI: 0
[  215.513253] sd 1:0:0:0: [sdb] 129630208 512-byte logical blocks: (66.4 GB/61.8 GiB)
[  215.521249] sd 1:0:0:0: [sdb] Write Protect is off
[  215.526371] sd 1:0:0:0: [sdb] No Caching mode page found
[  215.531737] sd 1:0:0:0: [sdb] Assuming drive cache: write through
[  215.561450]  sdb: sdb1
[  215.566167] sd 1:0:0:0: [sdb] Attached SCSI removable disk

Additional information

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

Accessing the peripheral MITO 8M Mini

Linux messages at boot time

...
...
[    4.954820] usb_otg_vbus: disabling
...
...

Usage with mass-storage

root@desk-mx8mm:~# 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, 0.844688 s, 318 MB/s
root@desk-mx8mp:~# mkfs.msdos mass_storage
mkfs.fat 4.1 (2017-01-24)
root@desk-mx8mm:~# mkdir loop
root@desk-mx8mm:~# mount -o loop mass_storage loop
root@desk-mx8mm:~# echo "Test USB OTG with mass storage device" > loop/usb.txt
root@desk-mx8mm:~# umount loop
root@desk-mx8mm:~#

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

root@desk-mx8mm:~# modprobe g_mass_storage removable=y file=mass_storage
[  891.807023] Mass Storage Function, version: 2009/09/11
[  891.813145] LUN: removable file: (no medium)
[  891.818901] LUN: removable file: /home/root/mass_storage
[  891.824754] Number of LUNs=1
[  891.827901] g_mass_storage gadget: Mass Storage Gadget, version: 2009/09/11
[  891.834955] g_mass_storage gadget: userspace failed to provide iSerialNumber
[  891.842109] g_mass_storage gadget: g_mass_storage ready
root@desk-mx8mm:~#

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

root@desk-mx8mm:~# [  892.036840] 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).

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