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[=#u-boot]
= Venice U-Boot Bootloader
Gateworks supports the U-Boot Bootloader for the Venice product family.

The purpose of a bootloader is to load the Linux kernel and execute it passing it configuration parameters such as an optional kernel command-line, an optional initial ramdisk filesystem, and a device-tree.

The following items are supported in the Gateworks U-Boot for Venice:
 - IMX8M FEC GbE
 - IMX8MP EQOS GbE
 - USB Host support (USB Mass Storage and USB Networking for ASIX USB 2.0 USB Network device)
 - eMMC / microSD

The following items are not currently supported in the Gateworks U-Boot for Venice:
- PCIe support (include PCIe based Gbe)

Additional resources:
 * [http://dev.gateworks.com/venice/boot_firmware/ Pre-built boot firmware (updated from U-Boot/Linux)]
 * [http://dev.gateworks.com/venice/images/ firmware-venice* JTAG binaries]
 * [https://github.com/gateworks/uboot-venice source]

see [wiki:uboot] for more info


== Editing the environment
If you would like to modify the default environment you can edit the [https://github.com/Gateworks/bsp-venice/blob/master/venice.env venice/venice.env] in the Venice BSP.

[=#default]
== Restoring environment defaults 
The Venice boot firmware has a copy of the original U-Boot env that was created during build time.

To restore default bootloader environment variables:

- At the "Hit any key to stop autoboot:" prompt press any key.

- Execute the following command:
{{{#!bash
run restore_env && reset
}}}

[=#memmap]
== Memory Mapping
When working with boot firmware you are often dealing with choosing where to load in memory various components. Sometimes this is done by hard-coding addresses into U-Boot commands, using env variables, or hard coding them into the U-Boot build configuration files (ie binman node) or FIT image templates.

Here is what we recommend for memory mapping on the IMX8M{M,N,P} SoC's:
||= address   =||= var =||= Note =||
|| 0x00920000  || || ARM Trusted Firmware ||
|| 0x40000000  || || base of DRAM ||
|| 0x40200000  || kernel_comp_addr_r || CONFIG_TEXT_BASE: base of non-secure memory<BR>The ATF configures the first 2M of DRAM as secure for itself ||
|| 0x40310000  || || binman_fip image gets put here
|| 0x44000000  || || CONFIG_SPL_LOAD_FIT_ADDRESS (used for secure boot)
|| 0x48200000  || loadaddr, kernel_addr_r || CONFIG_SYS_LOAD_ADDR 
|| 0x50200000  || fdt_addr_r || area for loading fdt (128M above kernel_addr_r)
|| 0x50300000  || scriptaddr || area for loading script (512K above fdt_addr_r)
|| 0x7e000000  || || CFG_TZDRAM_START (secure boot with TEE; for 1GB DRAM boards)
|| 0x80000000  || || 1GB boundary ||
|| 0xbe000000  || || CFG_TZDRAM_START (secure boot with TEE; for 2GB DRAM boards)
|| 0xc0000000  || || 2GB boundary 
|| 0xfe000000  || || CGG_TZDRAM_START (secure boot with TEE; for 4GB DRAM boards)
|| 0x100000000 || || 3GB boundary ||
|| 0x140000000 || || 4GB boundary ||