COM iMX6 Linux

Storage Layout

Linux virtual machine for development

• Please have a look at: Virtual Machine for Application Development

Linux Kernel

How to build a Kernel

Get sources from Github 1. Start the Console on Linux 2. git clone https://github.com/dh-electronics/linux-imx6qdl.git --branch dev/4.4.60_dhcom 3. cd linux-imx6qdl Configure and build the Device Tree + Kernel 4. ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make imx6_dhcom_defconfig 5. ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make menuconfig (optional: If you want to add/remove Kernel features) 6. ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make dtbs 7. ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-4.9-2014.11-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make zImage The built imx6x-dhcom#Y-BOARD.dtb devicetree files are available in arch/arm/boot/dts x = s, dl, d, q # = 2 for HW200, 3 for HW300, 4 for HW400 Y = B for Base, H for Hi-Speed-Interfaces BOARD = pdk1, pdk2, ... The built zImage kernel file will you find in arch/arm/boot

Update the Kernel and Device Tree with U-Boot

Please refere to the DHCOM Update Mechanism for i.MX6.

Update Kernel and Device Tree on a running Linux

Kernel 1. Copy the kernel zImage file to the path /boot (You can rename it after the Kernel version zImage_X.Y.Z) 2. Check zImage_file variable in /boot/uLinuxEnv.txt (e.g. zImage_file=zImage_4.4.60) Device Tree 3. Copy the Device Tree *.dtb file to the path /boot/dtbs_X.Y.Z 4. Check fdt_file variable in /boot/uLinuxEnv.txt (e.g. fdtfile=/dtbs_4.4.60/imx6dl-dhcom4B-pdk2.dtb) Reboot System 5. Restart the system (e.g. reboot)

Make your own Device Tree for your board

The recommended proceeding for making your our Device Tree should be the following:

1. Clone the DH Device Tree Board file and change it to fit for your board

- Based on i.MX6 and PDK1 (works with i.MX6 HW200)

imx6qdl-dh_pdk1.dtsi --> imx6qdl-COMPANY_BOARDNAME.dtsi

- Based on i.MX6 and PDK2 (works with i.MX6 HW300)

imx6qdl-dh_pdk2.dtsi --> imx6qdl-COMPANY_BOARDNAME.dtsi

2. Clone the main Device Tree file and change the included boad file to yours

E.g. based on i.MX6DL HW300 with PDK2

imx6dl-dhcom3B-pdk2.dts --> imx6dl-dhcom3B-BOARDNAME.dts

3. Add your new main Device Tree file to Makefile (located in the same folder)

DH Device Tree pattern (Kernel 4.4.x):

Rootfilesystem

Available Rootfilesystems

Please have a look at the iMX6 Images section.

Login

dhcom login: root Password: foo

Reboot

# reboot

or

# shutdown -r now

Shutdown

# poweroff

or

# shutdown -h now

Note: If the watchdog is active, the system will be reset.

Calibrating the touchscreen (only on Debian 6.0)

# ts_calibrate

Check the enviroment variable "TSLIB_TSDEVICE=/dev/input/event0" with printenv if an error occurs.

How to calibrate resistive touchscreens (only on Yocto images)

On devices with resistive touchscreens, the touchscreen has to be calibrated.

At our yocto images, we usually use libinput as library for handling input.

Prerequisites

• Yocto packages weston, weston-init and weston-examples have to be installed inside the image.
• The config file /etc/xdg/weston/weston.ini needs the following lines (to enable touchscreen calibration):

[libinput]
touchscreen_calibrator=true

After changing the configuration of weston, weston needs to be restarted:

systemctl restart weston

Steps for calibration

1. Get the touchscreen device name with weston-touch-calibrator

XDG_RUNTIME_DIR=/var/run/user/$(id -u weston) weston-touch-calibrator

Example result (bold part is needed for next steps):

device "/sys/devices/platform/soc/2100000.bus/21a8000.i2c/i2c-2/2-0049/input/input0/event0" - head "DPI-1"

2. Run weston-touch-calibrator on the device for starting the calibration. With the example part of the last result, the command looks like this (bold part is from the last result):

XDG_RUNTIME_DIR=/var/run/user/$(id -u weston) weston-touch-calibrator -v /sys/devices/platform/soc/2100000.bus/21a8000.i2c/i2c-2/2-0049/input/input0/event0

Now you press the highlighted points at the touchscreen to calibrate it. You will now get an output on the console like this (the important part is marked bold):

Calibration values: -0.001472 -1.081086 1.033880 -1.135099 0.000319 1.082698

3. To make the calibration permanent, you need to add a udev rule. Create the file /etc/udev/rules.d/touchscreen-cal.rules and use the calibration values there. With the result of the previous example, the file looks like this (bold part is the result of the last example):

SUBSYSTEM=="input", KERNEL=="event[0-9]*", ENV{ID_INPUT_TOUCHSCREEN}=="1", ENV{LIBINPUT_CALIBRATION_MATRIX}="-0.001472 -1.081086 1.033880 -1.135099 0.000319 1.082698"

Kernel Userspace Interfaces to Access Hardware

Ethernet Interfaces

DHCOM ENET 1	ethsom0
DHCOM ENET 2	ethsom1

Serial (UART) Interfaces

DHCOM (FF) UART 1	/dev/ttymxc0
DHCOM (BT) UART 2	/dev/ttymxc4
DHCOM (STD) UART 3	/dev/ttymxc3

I2C Interfaces

Hardware revision 300 and newer (dhcom3.., dhcom4.., ...)

DHCOM I2C 1	/dev/i2c-1
DHCOM I2C 2	/dev/i2c-0
On Module Devices	/dev/i2c-2

Hardware revision 100 / 200 (dhcom1.. / dhcom2..)

DHCOM I2C 1	/dev/i2c-0
DHCOM I2C 2	/dev/i2c-1
On Module Devices	/dev/i2c-2

SPI Interfaces

Device	Kernel <= 5.4.xxx	Kernel >= 5.10.xxx
DHCOM SPI 1	/dev/spidev0.2	/dev/spidev0.1
DHCOM SPI 2	/dev/spidev1.0	/dev/spidev1.0

Remark: DHCOM SPI1 interface doesn‘t work with DHCOM Premium Developer Kit (HD00013).

Reason: At DHCOM Premium Developer Kit SPI 1 isn‘t connected, because otherwise i.MX6 doesn‘t boot with the current schematic.

MMC/SD/eMMC Interfaces

DHCOM SD-Interface	/dev/mmcblk0pX
on module µSD Card	/dev/mmcblk1pX
on module eMMC	/dev/mmcblk2pX

'X' has to be replaced with the partition number

Control the display brightness

Set brightness level (X = 0...10)

echo X >/sys/class/backlight/display/brightness

Control GPIOs

See which gpio is already used by the system

cat /sys/kernel/debug/gpio | grep -v "gpio-... ( " or gpioinfo | grep -v unnamed

DHCOM Name:	alt. DHCOM Name:	SO-DIMM Pin#	CPU Pad Name	Linux <GPIO#> *	gpiod label (deprecated):	gpiod label:
GPIO A		154	PAD_GPIO_2	2	A	DHCOM-A
GPIO B		156	PAD_GPIO_4	4	B	DHCOM-B
GPIO C		162	PAD_GPIO_5	5	C	DHCOM-C
GPIO D		163	PAD_CSI0_DAT17	163	D	DHCOM-D
GPIO E		164	PAD_GPIO_19	101	E	DHCOM-E
GPIO F		165	PAD_DI0_PIN4	116	F	DHCOM-F
GPIO G		167	PAD_EIM_D27	91	G	DHCOM-G
GPIO H		173	PAD_KEY_ROW0	103	H	DHCOM-H
GPIO I		175	PAD_KEY_COL1	104	I	DHCOM-I
GPIO J	CIF HSYNC	74	PAD_NANDF_CS1	174	J	DHCOM-J
GPIO K	CIF PCLK	72	PAD_NANDF_CS2	175	K	DHCOM-K
GPIO L	CIF MCLK	70	PAD_KEY_ROW1	105	L	DHCOM-L
GPIO M	CIF VSYNC	68	PAD_SD3_DAT5	192	M	DHCOM-M
GPIO N	CIF D9	66	PAD_SD3_DAT4	193	N	DHCOM-N
GPIO O	CIF D8	64	PAD_CSI0_VSYNC	149	O	DHCOM-O
GPIO P	CIF D7	62	PAD_GPIO_18	205	P	DHCOM-P
GPIO Q	CIF D6	60	PAD_SD1_CMD	18	Q	DHCOM-Q
GPIO R	CIF D5	58	PAD_SD1_DAT0	16	R	DHCOM-R
GPIO S	CIF D4	56	PAD_SD1_DAT1	17	S	DHCOM-S
GPIO T	CIF D3	54	PAD_SD1_DAT2	19	T	DHCOM-T
GPIO U	CIF D2	52	PAD_SD1_CLK	20	U	DHCOM-U
GPIO V	CIF D1	50	PAD_CSI0_PIXCLK	146	V	DHCOM-V
GPIO W	CIF D0	48	PAD_CSI0_MCLK	147	W	DHCOM-W
INT HIGHEST PRIORITY		151	PAD_KEY_COL0	102	INT	DHCOM-INT

* = Valid if you didn't change the CONFIG_ARCH_NR_GPIO value in kernel config AND if your kernel doesn't probe another GPIO controller before the imx6 GPIO controller

Remark: Depending on your board configuration some of the additional gpios shared with the camera interface are not available on your system.

GPIO pin configuration

The default Linux Device Tree pin configurarion of the DHCOM GPIOs A - W is 0x400120b0

Pad Mux Register (0x020E_xxxx) = 0x0000_0015 SION: 1 Enabled (Force input path of pad) MUX_MODE: 0101 ALT5 Pad Control Register (0x020E_xxxx) = 0x0001_20B0 HYS: 1 Hysteresis enabled (Schmitt trigger input) ============== PUS: 00 100k Pull Down PUE: 1 PULL (Pull enabled) PKE: 0 Disable (Pull/Keeper disabled) ODE: 0 Disable (Output is CMOS) RESERVED: 000 -------------- SPEED: 10 imx6: 100MHz (medium) imx6ull: 100MHz (medium) DSE: 110 Drive strength imx6: 40 Ohm imx6ull: 43 Ohm @ 3.3V RESERVED 00 SRE: 0 SLOW (Slow Slew Rate)

Controlled by gpiod tools (need Kernel v4.7 or higher)

Set state

gpioset $(gpiofind GPIO_LABEL)=0

gpioset $(gpiofind GPIO_LABEL)=1

Get state

gpioget $(gpiofind GPIO_LABEL)

gpioget $(gpiofind GPIO_LABEL)

Remark: GPIO_LABEL could be DHCOM-A, DHCOM-B, DHCOM-C, ... see table above

Controlled by sysfs (since Kernel v4.8 deprecated)

Export

echo <GPIO#> >/sys/class/gpio/export

Remark: Have a look into /sys/class/gpio/ for already configured gpios.

Set direction

echo in >/sys/class/gpio/gpio<GPIO#>/direction

echo out >/sys/class/gpio/gpio<GPIO#>/direction

Set state

echo 0 >/sys/class/gpio/gpio<GPIO#>/value

echo 1 >/sys/class/gpio/gpio<GPIO#>/value

Get state

cat /sys/class/gpio/gpio<GPIO#>/value

Initialize and Test CAN Interface

Initialize:

ip link set can0 up type can bitrate 500000

Send test message via cansend (part of can-utils):

cansend can0 100#11.2233.44556677.88

Receive can messages (part of can-utils):

candump can0

Get can-utils:

apt-get install can-utils

Parallel Address- / Databus

To use the 16-bit address / databus from Linux userspace you can use the UIO driver interface. To enable and configure the interface it is necessary to setup the WEIM controller with the device tree. See the documentation of the device tree bindings of weim here.

Here is an example code which demonstrates how to do enable and configure the WEIM interface (parallel address- / databus):

&weim { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_dhcom_weim &pinctrl_dhcom_weim_cs0 &pinctrl_dhcom_weim_cs1>; #address-cells = <2>; #size-cells = <1>; /* it is necessary to setup 2x 64MB otherwise setting gpr fails */ ranges = <0 0 0x08000000 0x04000000>, // Chip select 0 == DHCOM CS A <1 0 0x0c000000 0x04000000>; // Chip select 1 == DHCOM CS B fsl,weim-cs-gpr = <&gpr>; status = "okay"; uiomap_cs0@0,0 { compatible = "generic-uio"; reg = <0 0x00000000 0x04000000>; reg-names = "uio_cs0"; interrupt-parent = <&gpio1>; interrupts = <2 2>; // Add gpio A == interrupt #address-cells = <1>; #size-cells = <1>; fsl,weim-cs-timing = <0x00610089 0x00001002 0x0F011061 0x00000000 0x0F068A31 0x00000000>; status = "okay"; }; uiomap_cs1@0,1 { compatible = "generic-uio"; reg = <1 0x00000000 0x04000000>; reg-names = "uio_cs1"; interrupt-parent = <&gpio1>; interrupts = <4 2>; // Add gpio B == interrupt #address-cells = <1>; #size-cells = <1>; fsl,weim-cs-timing = <0x00610089 0x00001002 0x0F011061 0x00000000 0x0F068A31 0x00000000>; status = "disabled"; }; };

We have already written some demo code at /arch/arm/boot/dts/imx6qdl-dhcom_cfg-weim.dtsi. It is easy to enable in the matching device-tree file:

• /arch/arm/boot/dts/imx6s-dhcom3B-pdk2.dts
• /arch/arm/boot/dts/imx6dl-dhcom3B-pdk2.dts
• /arch/arm/boot/dts/imx6d-dhcom3B-pdk2.dts
• /arch/arm/boot/dts/imx6q-dhcom3B-pdk2.dts

- // #include "imx6qdl-dhcom_cfg-weim.dtsi + #include "imx6qdl-dhcom_cfg-weim.dtsi

To use the generic uio driver it has to be enabled in the kernel configuration (make menuconfig)

• Device Drivers -> Userspace I/O Drivers -> Userspace I/O platform driver with generic IRQ handling

The device-tree of_id of the uio driver has to be set via kernel command line

• Add "optargs='uio_pdrv_genirq.of_id=generic-uio'" to uLinuxEnv.txt

Example for a UIO userspace driver:

• uio_access.cpp
• for further information have a look at the paper Userspace I/O drivers in a realtime context

Configure your own display

To configure your own display you have to do the following steps:

1. Configure your display and build a settings file by our tool DHCOMSettingsGenerator (Download v2.0.0.2)

2. Place generated file into the first partition (label: "boot")

3. Create a symbolic link to the file settings.bin ($ ln -s YourSettingsFile.bin settings.bin)

Remake: It is still possible to config the display via Device Tree e.g. dev/4.4.60_dhcom/arch/arm/boot/dts/imx6qdl-dh_pdk2.dtsi (not recommended by DH)

The following picture showing the sequence and priorities:

For detailed description of the display boot args please have a look at Display and Hardware settings of the iMX6 Bootloader.

Additional Information

• Linux Kernel Features
• Embedded Linux Build Environment (ELBE)