NXP i.MX 7 Computer on Module - Colibri iMX7

Overview

The i.MX7 SoC is a Hybrid multi-core processor composed by Single/Dual Cortex A7 core and Single Cortex M4 core. Zephyr was ported to run on the M4 core. In a later release, it will also communicate with the A7 core (running Linux) via RPmsg.

Hardware

i.MX7 Single/Dual Cortex A7 (800MHz/1.0GHz) core and Single Cortex M4 (200MHz) core
Memory
- RAM -> A7: 256MB, 512MB and 1GB
- RAM -> M4: 3x32KB (TCML, TCMU, OCRAM_S), 1x128KB (OCRAM) and 1x256MB (DDR)
- Flash -> A7: 4Gb eMMC and 512Mb NAND
Display
- RGB 1920x1080x24bpp
- 4-wire Resistive touch
Multimedia
- 1x Camera Parallel Interface
- 1x Analog Audio Line in (Stereo)
- 1x Analog Audio Mic in (Mono)
- 1x Analog Audio Headphone out (Stereo)
Connectivity
- USB 2.0 OTG (High Speed)
- USB 2.0 host (High Speed)
- 10/100 Mbit/s Ethernet PHY
- 4x I2C
- 4x SPI
- 7x UART
- 1x IrDA
- 20x PWM
- Up to 125 GPIO
- 4x Analog Input (12 Bit)
- 2x SDIO/SD/MMC (8 Bit)
- 2x CAN

For more information about the i.MX 7 SoC, Colibri iMX7 Computer on Module and Colibri Evaluation Board, see these references:

Supported Features

The Colibri iMX7D Computer on Module with Colibri Evaluation Board configuration supports the following hardware features on the Cortex M4 Core:

Interface	Controller	Driver/Component
NVIC	on-chip	nested vector interrupt controller
SYSTICK	on-chip	systick
GPIO	on-chip	gpio
I2C	on-chip	i2c
PWM	on-chip	pwm
UART	on-chip	serial port-polling; serial port-interrupt

The default configuration can be found in the defconfig file:

boards/toradex/colibri_imx7d/colibri_imx7d_mcimx7d_m4_defconfig

Other hardware features are not currently supported by the port.

Connections and IOs

The Colibri iMX7D Computer on Module with Colibri Evaluation Board was tested with the following pinmux controller configuration.

Board Name	SoC Name	Usage
UART_B RXD	UART2_TXD	UART Console
UART_B TXD	UART2_RXD	UART Console
SODIMM_135	GPIO1_IO02	LED0
SODIMM_133	GPIO2_IO26	SW0
SODIMM_194	I2C4_SDA	I2C_SDA
SODIMM_196	I2C4_SCL	I2C_SCL
SODIMM_59	PWM1/GPIO1_IO08	PWM

System Clock

The M4 Core is configured to run at a 200 MHz clock speed.

Serial Port

The iMX7D SoC has seven UARTs. The number 2 is configured for the console and the remaining are not used/tested.

Programming and Debugging

The Colibri iMX7D doesn’t have QSPI flash for the M4 and it needs to be started by the A7 core. The A7 core is responsible to load the M4 binary application into the RAM, put the M4 in reset, set the M4 Program Counter and Stack Pointer, and get the M4 out of reset. The A7 can perform these steps at bootloader level or after the Linux system has booted.

The M4 can use up to 5 different RAMs. These are the memory mapping for A7 and M4:

Region	Cortex-A7	Cortex-M4 (System Bus)	Cortex-M4 (Code Bus)	Size
DDR	0x80000000-0xFFFFFFFF	0x80000000-0xDFFFFFFF	0x10000000-0x1FFEFFFF	2048MB (less for M4)
OCRAM	0x00900000-0x0091FFFF	0x20200000-0x2021FFFF	0x00900000-0x0091FFFF	128KB
TCMU	0x00800000-0x00807FFF	0x20000000-0x20007FFF		32KB
TCML	0x007F8000-0x007FFFFF		0x1FFF8000-0x1FFFFFFF	32KB
OCRAM_S	0x00180000-0x00187FFF	0x20180000-0x20187FFF	0x00000000-0x00007FFF	32KB
QSPI Flash			0x08000000-0x0BFFFFFF	64MB

References

i.MX 7 Dual Reference Manual from page 190 (section 2.1.2 and 2.1.3)
Toradex Wiki

At compilation time you have to choose which RAM will be used. This configuration is done in the file boards/toradex/colibri_imx7d/colibri_imx7d_mcimx7d_m4.dts with “zephyr,flash” (when CONFIG_XIP=y) and “zephyr,sram” properties. The available configurations are:

"zephyr,flash"
- &ddr_code
- &tcml_code
- &ocram_code
- &ocram_s_code
- &ocram_pxp_code
- &ocram_epdc_code

"zephyr,sram"
- &ddr_sys
- &tcmu_sys
- &ocram_sys
- &ocram_s_sys
- &ocram_pxp_sys
- &ocram_epdc_sys

Below you will find the instructions to load and run Zephyr on M4 from A7 using u-boot.

Copy the compiled zephyr.bin to the first EXT partition of the SD card and plug into the board. Power it up and stop the u-boot execution. Set the u-boot environment variables and run the zephyr.bin from the appropriated memory configured in the Zephyr compilation:

setenv bootm4 'ext4load mmc 0:1 $m4addr $m4fw && dcache flush && bootaux $m4addr'
# TCML
setenv m4tcml 'setenv m4fw zephyr.bin; setenv m4addr 0x007F8000'
setenv bootm4tcml 'run m4tcml && run bootm4'
run bootm4tcml
# TCMU
setenv m4tcmu 'setenv m4fw zephyr.bin; setenv m4addr 0x00800000'
setenv bootm4tcmu 'run m4tcmu && run bootm4'
run bootm4tcmu
# OCRAM
setenv m4ocram 'setenv m4fw zephyr.bin; setenv m4addr 0x00900000'
setenv bootm4ocram 'run m4ocram && run bootm4'
run bootm4ocram
# OCRAM_S
setenv m4ocrams 'setenv m4fw zephyr.bin; setenv m4addr 0x00180000'
setenv bootm4ocrams 'run m4ocrams && run bootm4'
run bootm4ocrams
# DDR
setenv m4ddr 'setenv m4fw zephyr.bin; setenv m4addr 0x80000000'
setenv bootm4ddr 'run m4ddr && run bootm4'
run bootm4ddr

M4<->Linux IPC using RPMSG

The IMX7D soc supports the subsys/ipc/openamp_rsc_table sample to demonstrate the usage of rpmsg_tty as an inter processor communication.

The board configuration is provided for the colibri_imx7d board. The boot process of the M4 core is handled solely by the Linux kernel using the RPROC framework.

The sample was tested with Toradex’s LTS BSP 6.6.0 Minimal Open Embedded image with upstream Linux kernel 6.1.83.

Required kernel modules must be loaded for RPMSG to work:

imx_rproc
virtio_rpmsg_bus
rpmsg_tty (requiring rpmsg_core)

You need to modify your Linux device tree to add the M4 definitions:

Enable MU_A
Reserve memory areas for the M4 so Linux won’t touch them.
Define the M4 remoteproc node for the drivers.

If you have not downloaded the BSP sources, you can modify the board’s device tree from its currently loaded dtb file.

#Check the which fdtfile is loaded for your board in U-boot
printenv
#For a Colibri_imx7d on Viola Carrier on BSP 6.6.0
fdtfile = imx7d-colibri-emmc-eval-v3.dtb

#Copy this file to your Linux PC through SSH from /boot
#Convert the dtb into a dts
dtc -I dtb -O dts -f imx7d-colibri-emmc-eval-v3.dtb -o imx7d-colibri-emmc-eval-v3.dts

#You need to find the following phandle numbers:
# reset-controller
# mailbox@30aa0000

#Note down the phandle value (0xbd)
grep -A10 "mailbox@30aa0000 {" imx7d-colibri-emmc-eval-v3.dts
# outputs your DTS's mailbox definition
#            mailbox@30aa0000 {
#                    compatible = "fsl,imx7s-mu\0fsl,imx6sx-mu";
#                    reg = <0x30aa0000 0x10000>;
#                    interrupts = <0x00 0x58 0x04>;
#                    clocks = <0x01 0x1b1>;
#                    #mbox-cells = <0x02>;
#                    status = "disabled";
#                    phandle = <0xbd>;
#            };

#Note down the phandle value (0x32)
grep -A8 "reset-controller@30390000 {" imx7d-colibri-emmc-eval-v3.dts
# outputs your DTS's reset-controller definition
#            reset-controller@30390000 {
#                    compatible = "fsl,imx7d-src\0syscon";
#                    reg = <0x30390000 0x10000>;
#                    interrupts = <0x00 0x59 0x04>;
#                    #reset-cells = <0x01>;
#                    phandle = <0x32>;
#            };

#Node down the biggest phandle value
grep "phandle = <" imx7d-colibri-emmc-eval-v3.dts | sort -r | head -1
# outputs your DTS's largest phandle definition
#            phandle = <0xca>;

#Now we can add our nodes to the .dts file:
cp imx7d-colibri-emmc-eval-v3.dts imx7d-m4.dts
nano imx7d-m4.dts

#Modify MU_A node to enable it
mailbox@30aa0000 {
   compatible = "fsl,imx7s-mu\0fsl,imx6sx-mu";
   reg = <0x30aa0000 0x10000>;
   interrupts = <0x00 0x58 0x04>;
   clocks = <0x01 0x1b1>;
   #mbox-cells = <0x02>;
   status = "okay";
   phandle = <0xbd>;
};

#Add these definitions under / { } just before the __symbols__
#Disgard the comments with #-->
reserved-memory {
   #address-cells = <0x01>;
   #size-cells = <0x01>;
   ranges;

   vdev0buffer0@90002000 {
      compatible = "shared-dma-pool";
      reg = <0x90002000 0x8000>;
      no-map;
      phandle = <0xcb>; #--> biggest phandle +1
   };

   vdev0vring0@90000000 {
      compatible = "shared-dma-pool";
      reg = <0x90000000 0x1000>;
      no-map;
      phandle = <0xcc>; #--> biggest phandle +2
   };

   vdev0vring1@90001000 {
      compatible = "shared-dma-pool";
      reg = <0x90001000 0x1000>;
      no-map;
      phandle = <0xcd>; #--> biggest phandle +3
   };

   cm4tcmcode@7f8000 {
      compatible = "shared-dma-pool";
      reg = <0x7f8000 0x8000>;
      no-map;
      phandle = <0xce>; #--> biggest phandle +4
   };

   cm4sramcode@900000 {
      compatible = "shared-dma-pool";
      reg = <0x900000 0x40000>;
      no-map;
      phandle = <0xcf>; #--> biggest phandle +5
   };

   cm4reserved@8ff00000 {
      compatible = "shared-dma-pool";
      reg = <0x8ff00000 0x100000>;
      no-map;
      phandle = <0xd0>; #--> biggest phandle +6
   };
};

imx7d-cm4 {
   compatible = "fsl,imx7d-cm4";
   mbox-names = "tx\0rx\0rxdb";
   mboxes = <0xbd 0x00 0x00 0xbd 0x01 0x00 0xbd 0x03 0x00>; #--> MU_A phandle (0xbd)
   memory-region = <0xcb 0xcc 0xcd 0xce 0xcf 0xd0>; #--> All the previously defined phandles
   syscon = <0x32>; #--> phandle for the reset-controller
   clocks = <0x01 0x42>;
};

#Recompile the dts into a dtb
dtc -I dts -O dtb -f imx7d-m4.dts -o imx7d-m4.dtb

#Copy the new dtb to /boot on the Colibri IMX7 board
#Start in U-boot and update the device-tree
setenv fdtfile imx7d-m4.dtb
saveenv
boot

When the OS has finished booting with your new device tree you can enable the drivers and start the M4 core.

#Copy zephyr_openamp_rsc_table.elf to /lib/firmware on your board
$ modprobe imx_rproc
$ modprobe virtio_rpmsg_bus
$ modprobe rpmsg_tty

#Request RPROC to load the M4 image
$ echo stop > /sys/class/remoteproc/remoteproc0/state
$ echo zephyr_openamp_rsc_table.elf > /sys/class/remoteproc/remoteproc0/firmware
$ echo start > /sys/class/remoteproc/remoteproc0/state

#dmesg will detail the boot process:
$ dmesg
[  497.120499] remoteproc remoteproc0: stopped remote processor imx-rproc
[  497.138938] remoteproc remoteproc0: powering up imx-rproc
[  497.168735] remoteproc remoteproc0: Booting fw image zephyr_openamp_rsc_table.elf, size 1267076
[  497.184826] rproc-virtio rproc-virtio.1.auto: assigned reserved memory node vdev0buffer0@90002000
[  497.221395] virtio_rpmsg_bus virtio0: rpmsg host is online
[  497.233806] virtio_rpmsg_bus virtio0: creating channel rpmsg-tty addr 0x400
[  497.236666] rproc-virtio rproc-virtio.1.auto: registered virtio0 (type 7)
[  497.259822] remoteproc remoteproc0: remote processor imx-rproc is now up
[  497.293913] virtio_rpmsg_bus virtio0: creating channel rpmsg-client-sample addr 0x401
[  497.308388] rpmsg_client_sample virtio0.rpmsg-client-sample.-1.1025: new channel: 0x401 -> 0x401!
[  497.337969] virtio_rpmsg_bus virtio0: creating channel rpmsg-tty addr 0x402

$ ls /dev | grep ttyRPMSG
ttyRPMSG0 -> used for zephyr shell interface
ttyRPMSG1 -> used for sample interface

Debugging

Download and install J-Link Tools and NXP iMX7D Connect CortexM4.JLinkScript.

To run Zephyr Binary using J-Link create the following script in order to get the Program Counter and Stack Pointer from zephyr.bin.

get-pc-sp.sh:

#!/bin/sh

firmware=$1

pc=$(od -An -N 8 -t x4 $firmware | awk '{print $2;}')
sp=$(od -An -N 8 -t x4 $firmware | awk '{print $1;}')

echo pc=$pc
echo sp=$sp

Get the SP and PC from firmware binary: ./get-pc-sp.sh zephyr.bin

pc=00900f01
sp=00905020

Plug in the J-Link into the board and PC and run the J-Link command line tool:

/usr/bin/JLinkExe -device Cortex-M4 -if JTAG -speed 4000 -autoconnect 1 -jtagconf -1,-1 -jlinkscriptfile iMX7D_Connect_CortexM4.JLinkScript

The following steps are necessary to run the zephyr.bin: 1. Put the M4 core in reset 2. Load the binary in the appropriate addr (TMCL, TCMU, OCRAM, OCRAM_S or DDR) 3. Set PC (Program Counter) 4. Set SP (Stack Pointer) 5. Get the M4 core out of reset

Issue the following commands inside J-Link commander:

w4 0x3039000C 0xAC
loadfile zephyr.bin,0x00900000
w4 0x00180000 00900f01
w4 0x00180004 00905020
w4 0x3039000C 0xAA

With these mechanisms, applications for the colibri_imx7d/imx7d/m4 board configuration can be built and debugged in the usual way (see Building an Application and Run an Application for more details).