COM iMX6ULL Linux: Difference between revisions

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Latest revision as of 10:52, 21 September 2021

Storage Layout

Linux virtual machine for development

Please have a look at: Virtual Machine for Application 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/4.19.135_dhsom` 3. `cd linux-imx6qdl`

Configure and build the Device Tree + Kernel

4. `ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-6.3.1-2017.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make imx6ull_dhsom_defconfig` 5. `ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-6.3.1-2017.05-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-6.3.1-2017.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make dtbs` 7. `ARCH=arm CROSS_COMPILE=/opt/gcc-linaro-6.3.1-2017.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf- make zImage`

The built imx6ull-dhcom-BOARD.dtb / imx6ull-dhcor-BOARD.dtb devicetree files are available in arch/arm/boot/dts
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_4.19.25`)

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

Ethernet Interfaces

DHCOM ENET 1	`ethsom0`
DHCOM ENET 2	`ethsom1`

Serial (UART) Interfaces

DHCOM UART 1	`/dev/ttymxc0`
DHCOM UART 2 ^[1]	`/dev/ttymxc1`
DHCOM UART 3	`<n/a>`

^[1] If DHCOM UART2 is used for Bluetooth it is possible to have it on a modified module hardware on /dev/ttymxc5 by losing GPIOs J/K/L/M.

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 ^[1]	`/dev/spidev1.0`

^[1] DHCOM SPI2 is only available, if the second ethernet is not mounted.

MMC/SD/eMMC Interfaces

DHCOM SD-Interface	`/dev/mmcblk1pX`
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 \| 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_SNVS_TAMPER0	128	A	DHCOM-A
GPIO B		156	PAD_SNVS_TAMPER1	129	B	DHCOM-B
GPIO C		162	PAD_SNVS_TAMPER2	130	C	DHCOM-C
GPIO D		163	PAD_SNVS_TAMPER3	131	D	DHCOM-D
GPIO E		164	PAD_SNVS_TAMPER4	132	E	DHCOM-E
GPIO F		165	PAD_SNVS_TAMPER7	135	F	DHCOM-F
GPIO G		167	PAD_SNVS_TAMPER8	136	G	DHCOM-G
GPIO H		173	PAD_SNVS_TAMPER9	137	H	DHCOM-H
GPIO I		175	PAD_UART1_CTS_B	18	I	DHCOM-I
GPIO J	CIF HSYNC	74	PAD_CSI_HSYNC	116	J	DHCOM-J
GPIO K	CIF PCLK	72	PAD_CSI_PIXCLK	114	K	DHCOM-K
GPIO L	CIF MCLK	70	PAD_CSI_MCLK	113	L	DHCOM-L
GPIO M	CIF VSYNC	68	PAD_CSI_VSYNC	115	M	DHCOM-M
GPIO N	CIF D9	66	PAD_CSI_DATA07	124	N	DHCOM-N
GPIO O	CIF D8	64	PAD_CSI_DATA06	123	O	DHCOM-O
GPIO P	CIF D7	62	PAD_CSI_DATA05	122	P	DHCOM-P
GPIO Q	CIF D6	60	PAD_CSI_DATA04	121	Q	DHCOM-Q
GPIO R	CIF D5	58	PAD_CSI_DATA03	120	R	DHCOM-R
GPIO S	CIF D4	56	PAD_CSI_DATA02	119	S	DHCOM-S
GPIO T	CIF D3	54	PAD_CSI_DATA01	118	T	DHCOM-T
GPIO U	CIF D2	52	PAD_CSI_DATA00	117	U	DHCOM-U
GPIO V	CIF D1	50	<n/a>	<n/a>	<n/a>	<n/a>
GPIO W	CIF D0	48	<n/a>	<n/a>	<n/a>	<n/a>
INT HIGHEST PRIORITY		151	PAD_KEY_COL0	11	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`

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"; }; };

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