CL-SOM-iMX7: U-Boot: Firmware Overview

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Introduction

This article describes the firmware for CL-SOM-iMX7 system-on-module. CL-SOM-iMX7 firmware consists of a single binary: U-Boot image. The i.MX7 boot ROM tries to boot U-Boot from either SD card, or SPI flash, as determined by the hardware boot selector (ALT BOOT button). U-Boot initializes hardware modules necessary for system boot and loads the operating system.

Package contents

cl-som-imx7-u-boot/
├── images
│   └── cl-som-imx7-firmware
├── README.txt
└── u-boot
    ├── patches
    │   ├── 0001-arm-imx7d-add-support-for-Compulab-cl-som-imx7.patch
    │   ├── ...
    │   └── 0008-arm-imx7d-cl-som-imx7-add-extraversion.patch
    ├── u-boot-v2016.09-cl-som-imx7-0.91.bin
    └── u-boot-v2016.09-cl-som-imx7-0.91.patch

images

  • cl-som-imx7-firmware - CL-SOM-iMX7 firmware binary

u-boot

  • u-boot-v2016.09-cl-som-imx7-0.91.bin - U-Boot binary
  • u-boot-v2016.09-cl-som-imx7-0.91.patch - patch vs. v2016.09 mainline U-Boot
  • patches - ordered collection of patches, that form the single patch above (u-boot-v2016.09-cl-som-imx7-0.91.patch)

U-Boot

U-Boot is the bootloader used on CL-SOM-iMX7. It allows flexible selection of operating system boot modes, provides scripting facilities and command line interface through a serial port. U-Boot allows booting operating system from the on-board eMMC flash, removable storage (e.g. USB drive, SD/MMC card), or the network (TFTP/NFS server).

Please consult U-Boot quick reference and U-Boot project documentation for U-Boot features and commands description.

U-Boot environment

U-Boot environment resides on the SPI flash, regardless of the boot source. The environment resides at offset 0xC0000 from the start of SPI flash, and its size is 8KiB.

Boot sources

CM-FX6 can boot from either a micro SD card, or the on-board SPI flash.

The following sections describe the layout of each storage type.

Default SPI flash mapping

Offset Description Size
0KB U-Boot 768KB
768KB U-Boot environment 256KB
1MB Splash image Remaining SPI flash space

Default SD card mapping

Offset Description Size
0KB Reserved/MBR 1KB
1KB U-Boot ~1MB
1MB Remaining SD-card space Remaining SD-card space
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