mirror of
https://github.com/AsahiLinux/u-boot
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141 lines
4.4 KiB
Text
141 lines
4.4 KiB
Text
---------------------------------------------
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UBL image Boot Image generation using mkimage
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---------------------------------------------
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This document describes how to set up an U-Boot image that can be directly
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booted by a DaVinci processor via NAND boot mode, using an UBL header,
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but without need for UBL.
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For more details see section 11.2 "ARM ROM Boot Modes" of
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http://focus.ti.com/lit/ug/sprufg5a/sprufg5a.pdf
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Command syntax:
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--------------
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./tools/mkimage -l <u-boot_file>
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to list the UBL image file details
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./tools/mkimage -T ublimage \
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-n <board specific configuration file> \
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-d <u-boot binary> <output image file>
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For example, for the davinci dm365evm board:
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./tools/mkimage -n ./board/davinci/dm365evm/ublimage.cfg \
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-T ublimage \
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-d u-boot-nand.bin u-boot.ubl
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You can generate the image directly when you compile u-boot with:
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$ make u-boot.ubl
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The output image can be flashed into the NAND.
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Please check the DaVinci documentation for further details.
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Board specific configuration file specifications:
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-------------------------------------------------
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1. This file must present in the $(BOARDDIR) and the name should be
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ublimage.cfg (since this is used in Makefile).
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2. This file can have empty lines and lines starting with "#" as first
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character to put comments.
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3. This file can have configuration command lines as mentioned below,
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any other information in this file is treated as invalid.
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Configuration command line syntax:
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---------------------------------
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1. Each command line must have two strings, first one command or address
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and second one data string
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2. Following are the valid command strings and associated data strings:-
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Command string data string
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-------------- -----------
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MODE UBL special mode, on of:
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safe
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Example:
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MODE safe
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ENTRY Entry point address for the user
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bootloader (absolute address) = TEXT_BASE
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nand_spl loader.
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Example:
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ENTRY 0x00000020
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PAGES Number of pages (size of user bootloader
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in number of pages)
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Example:
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PAGES 27
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START_BLOCK Block number where user bootloader is present
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Example:
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START_BLOCK 5
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START_PAGE Page number where user bootloader is present
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(for RBL always 0)
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Example:
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START_PAGE 0
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------------------------------------------------
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Structure of the u-boot.ubl binary:
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compile steps:
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1) nand_spl code compile, with pad_to = (TEXT_BASE +
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(CONFIG_SYS_NROF_PAGES_NAND_SPL * pagesize))
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Example: cam_enc_4xx pad_to = 0x20 + (6 * 0x800) = 0x3020 = 12320
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-> u-boot-spl-16k.bin
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!! TEXT_BASE = 0x20, as the RBL starts at 0x20
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2) compile u-boot.bin ("normal" u-boot)
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-> u-boot.bin
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3) create u-boot-nand.bin = u-boot-spl-16k.bin + u-boot.bin
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4) create u-boot.ubl, size = 1 page size NAND
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create UBL header and paste it before u-boot.bin
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This steps are done automagically if you do a "make all"
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-> You get an u-boot.ubl binary, which you can flash
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into your NAND.
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Structure of this binary (Example for the cam_enc_4xx board with a NAND
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page size = 0x800):
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offset : 0x00000 | 0x800 | 0x3800
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content: UBL | nand_spl | u-boot code
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Header | code |
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The NAND layout looks for example like this:
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(Example for the cam_enc_4xx board with a NAND page size = 0x800, block
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size = 0x20000 and CONFIG_SYS_NROF_UBL_HEADER 5):
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offset : 0x80000 | 0xa0000 | 0xa3000
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content: UBL | nand_spl | u-boot code
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Header | code |
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^ ^
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^ 0xa0000 = CONFIG_SYS_NROF_UBL_HEADER * 0x20000
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^
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0x80000 = Block 4 * 0x20000
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If the cpu starts in NAND boot mode, it checks the UBL descriptor
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starting with block 1 (page 0). When a valid UBL signature is found,
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the corresponding block number (from 1 to 24) is written to the last 32
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bits of ARM internal memory (0x7ffc-0x8000). This feature is provided
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as a basic debug mechanism. If not found, it continues with block 2
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... last possible block is 24
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If a valid UBL descriptor is found, the UBL descriptor is read and
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processed. The descriptor gives the information required for loading
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and control transfer to the nand_spl code. The nand_spl code is then
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read and processed.
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Once the user-specified start-up conditions are set, the RBL copies the
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nand_spl into ARM internal RAM, starting at address 0x0000: 0020.
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^^^^
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The nand_spl code itself now does necessary intializations, and at least,
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copies the u-boot code from NAND into RAM, and jumps to it ...
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------------------------------------------------
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Author: Heiko Schocher <hs@denx.de>
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