COM iMX6ULL Linux

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Storage Layout


DHCOM Boot Storage i.MX6ULL


DHCOM Storage Layout i.MX6ULL

Linux virtual machine for development

Linux Kernel

Sources: Look at page i.MX6ULL BSP Sources

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/4.19.25_dhsom
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 imx6ull_dhsom_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

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_4.19.25)

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_4.19.25/imx6ull-dhcom-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
imx6ull-dhcom-pdk2.dts --> imx6ull-dhcom-BOARDNAME.dts
2. Add your new main Device Tree file to Makefile (located in the same folder)

Debian Rootfilesystem

Available Rootfilesystems

Please have a look at the iMX6ULL 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.

Kernel Userspace Interfaces to Access Hardware

Serial (UART) Interfaces

DHCOM UART 1 /dev/ttymxc0
DHCOM UART 2 /dev/ttymxc1
DHCOM UART 3 <n/a>

I2C Interfaces

DHCOM I2C 1 /dev/i2c-1
DHCOM I2C 2 /dev/i2c-0

SPI Interfaces

DHCOM SPI 1 /dev/spidev0.0
DHCOM SPI 2 /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/mmcblk1pX
on module µSD Card
on module eMMC /dev/mmcblk2pX
'X' has to be replaced with the partition number

Control the display brightness

Coming soon

Control GPIOs

See which gpio is already used by the system
cat /sys/kernel/debug/gpio | grep -v "gpio-... ( "
DHCOM Name: gpiod label: alt. DHCOM Name: SO-DIMM Pin# CPU Pad Name Linux <GPIO#> *
GPIO A A 154 PAD_SNVS_TAMPER0 128
GPIO B B 156 PAD_SNVS_TAMPER1 129
GPIO C C 162 PAD_SNVS_TAMPER2 130
GPIO D D 163 PAD_SNVS_TAMPER3 131
GPIO E E 164 PAD_SNVS_TAMPER4 132
GPIO F F 165 PAD_SNVS_TAMPER7 135
GPIO G G 167 PAD_SNVS_TAMPER8 136
GPIO H H 173 PAD_SNVS_TAMPER9 137
GPIO I I 175 PAD_UART1_CTS_B 18
GPIO J J CIF HSYNC 74 PAD_CSI_HSYNC 116
GPIO K K CIF PCLK 72 PAD_CSI_PIXCLK 114
GPIO L L CIF MCLK 70 PAD_CSI_MCLK 113
GPIO M M CIF VSYNC 68 PAD_CSI_VSYNC 115
GPIO N N CIF D9 66 PAD_CSI_DATA07 124
GPIO O O CIF D8 64 PAD_CSI_DATA06 123
GPIO P P CIF D7 62 PAD_CSI_DATA05 122
GPIO Q Q CIF D6 60 PAD_CSI_DATA04 121
GPIO R R CIF D5 58 PAD_CSI_DATA03 120
GPIO S S CIF D4 56 PAD_CSI_DATA02 119
GPIO T T CIF D3 54 PAD_CSI_DATA01 118
GPIO U U CIF D2 52 PAD_CSI_DATA00 117
GPIO V CIF D1 50 <n/a> <n/a>
GPIO W CIF D0 48 <n/a> <n/a>
INT HIGHEST PRIORITY INT 151 PAD_KEY_COL0 11
* = 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.


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 A, B, 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

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 i.MX6 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: 
- // #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:

Configure your own display

Coming soon

Additional Information

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