u-boot/board/lego/ev3
David Lechner f4e2c10a71 ARM: legoev3: drop bi_arch_number
This drops assigning bi_arch_number on LEGO MINDSTORMS EV3. This board
never had its own unique number and since we are using device tree,
we no longer need to pass an arch number to Linux.

Signed-off-by: David Lechner <david@lechnology.com>
2021-02-04 20:37:56 +05:30
..
Kconfig arm: Add support for LEGO MINDSTORMS EV3 2016-03-14 19:18:40 -04:00
legoev3.c ARM: legoev3: drop bi_arch_number 2021-02-04 20:37:56 +05:30
MAINTAINERS arm: Add support for LEGO MINDSTORMS EV3 2016-03-14 19:18:40 -04:00
Makefile SPDX: Convert all of our single license tags to Linux Kernel style 2018-05-07 09:34:12 -04:00
README ARM: legoev3: convert to driver model 2019-07-13 11:11:28 -04:00

Summary
=======

LEGO MINDSTORMS EV3 is a toy robot produced by the LEGO Group. It is based
on the davinci da850 evm. The EV3 has a 16MB spi flash and a SDHC microSD card
reader.

Booting
=======

The EV3 contains a bootloader in EEPROM that loads u-boot.bin from address 0x0
of the SPI flash memory (with a size of 256KiB!). Because the EEPROM is read-
only and it takes care of low level configuration (PLL and DDR), we don't use
U-Boot to produce an SPL image.

Using the default configuration, U-Boot had a boot scrips that works as follows:

* Check to see if microSD card is present
* If it is, try to load boot.scr from the first FAT partition
* If loading boot.scr was successful, run it
* Otherwise, try loading uEnv.txt
* If loading uEnv.txt was successful, import it
* If there is a uenvcmd variable (from uEnv.txt), run it
* Try to load uImage from the first FAT partition
* If it was successful, try to load da850-lego-ev3.dtb
* If loading uImage was successful, boot it (DT is optional)
* If none of the above was successful, try booting from flash

Suggested Flash Memory Layout
=============================

The following is based on the default U-Boot configuration:

| Image (file)       | Start Addr. | Max. Size         |
+--------------------+-------------+-------------------+
| u-boot.bin         |         0x0 |  0x40000 (256KiB) |
| da850-lego-ev3.dtb |     0x40000 |  0x10000 (64KiB)  |
| uImage             |     0x50000 | 0x400000 (4MiB)   |
| rootfs (squashfs)  |    0x450000 | 0xa00000 (10MiB)  |

Writing image to flash
======================

The EEPROM contains a program for uploading an image file to the flash memory.
The program is started by holding down the right button on the EV3 when powering
it on. You can also `run fwupdateboot` in the u-boot shell to reboot into this
mode. The image can then be uploaded using the official LEGO MINDSTORMS EV3
software or a 3rd party program capable of uploading a firmware file.

If you are booting from the microSD card, it is enough to just write uboot.bin
to the flash. If you are not using a microSD card, you will need to create an
image file using the layout described above.

IMPORTANT: The EEPROM bootloader only copies 256k, so u-boot.img must not
exceed that size!