COM iMX6 Linux

Storage Layout

Linux virtual machine for development

Please have a look at: Virtual Machine for Application Development

Linux Kernel

Sources for the i.MX6 Kernel

Mainline

Vendor

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=arm-linux-gnueabihf- make imx6_dhcom_defconfig` 5. `ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make menuconfig` (optional: If you want to add/remove Kernel features) 6. `ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make dtbs` 7. `ARCH=arm CROSS_COMPILE=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 Devicetree with U-Boot

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

Update Kernel and Devicetree on a running Linux

Kernel

1. Copy the kernel zImage file to the path `/boot` 2. Check whether the correct zImage file name is set in `/boot/uLinuxEnv.txt` (e.g. `zImage_file=zImage`)

Devicetree

3. Copy the devicetree file to the path `/boot/dtbs` 4. Check fdtfile variable in `/boot/uLinuxEnv.txt` (e.g. `fdtfile=/dtbs/imx6dl-dhcom3B-pdk2.dtb` / see above)

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:

Debian Rootfilesystem

Available Rootfilesystems

Please have a look at the iMX6 Downloads section.

External Documentation

The Debian Administrator's Handbook: A reference book presenting the Debian distribution, from initial installation to configuration of services. The administration and configuration chapters apply to our Debian based root filesystems.
Debian Documentation

Login

`Debian GNU/Linux 8 dhcom ttymxc0` `dhcom login: root Password: foo`

Shutdown

`# shutdown -h now`

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 create a microSD-card with a rootfilesystem on it

1. Format a microSD card like following (in linux e.g. gparted, palimpsest) with Master Boot Record partition scheme

`P1 ext3, name="boot" (Primary partition: 100MiB)` `P2 ext3, name="rootfs" (Primary part.: Residual space)`

2. Untar the root file system to the "rootfs" partition of the microSD card (Don't copy the tar archive directly to the microSD card)

Start the Console on Linux `# su` `# chmod 755 /path/of/the/microSD_card` `# cd /path/of/the/microSD_card` `# tar xfjv path/to/RootFS/Name_of_RootFS_file.tar.bz2`

Remark: If you got a *.tar.gz file so type tar xfzv ... to extract the rootfilesystem.

Kernel Userspace Interfaces to Access Hardware

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

DHCOM SPI 1	`/dev/spidev0.2`
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/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

Coming soon

Control GPIOs

See which gpio is already used by the system

`cat /sys/kernel/debug/gpio`

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

* = 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 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:

Debian package containing can-utils (ARM)

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:

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.