projects / J-u-boot.git / blame
| Commit | Line | Data |
|---|---|---|
| 894c3ad2 TF |
1 | Summary |
| 2 | ======= | |
| 3 | ||
| 4 | This document describes how to use U-Boot on the Broadcom 7445 SoC, as | |
| 5 | a third stage bootloader loaded by Broadcom's BOLT bootloader. | |
| 6 | ||
| 7 | BOLT loads U-Boot as a generic ELF binary. Some U-Boot features such | |
| 8 | as networking are not yet available but other important features are, | |
| 9 | including: | |
| 10 | ||
| 11 | - ext4 file system traversal | |
| 12 | ||
| 13 | - support for loading FIT images | |
| 14 | ||
| 15 | - advanced scripting | |
| 16 | ||
| 17 | - support for FIT-provided DTBs instead of relying on the | |
| 18 | BOLT-provided DTB | |
| 19 | ||
| 20 | A customized version of this port has been used in production. The | |
| 21 | same approach may work on other BCM7xxx boards, with some | |
| 22 | configuration adjustments and memory layout experimentation. | |
| 23 | ||
| 24 | Build | |
| 25 | ===== | |
| 26 | ||
| 27 | make bcm7445_defconfig | |
| 28 | make | |
| 29 | ${CROSS_COMPILE}strip u-boot | |
| 30 | ||
| 31 | Run | |
| 32 | === | |
| 33 | ||
| 34 | Flash the u-boot binary into board storage, then invoke it from BOLT. | |
| 35 | For example: | |
| 36 | ||
| 37 | BOLT> boot -bsu -elf flash0.u-boot1 | |
| 38 | ||
| 39 | This port assumes that I-cache and D-cache are already enabled when | |
| 40 | U-Boot is entered. | |
| 41 | ||
| 42 | Flattened Image Tree Support | |
| 43 | ============================ | |
| 44 | ||
| 45 | What follows is an example FIT image source file. Build it with: | |
| 46 | ||
| 47 | mkimage -f image.its image.itb | |
| 48 | ||
| 49 | Booting the resulting image.itb was tested on BOLT v1.20, with the | |
| 50 | following kernels: | |
| 51 | ||
| 52 | https://github.com/Broadcom/stblinux-3.14 | |
| 53 | https://github.com/Broadcom/stblinux-4.1 | |
| 54 | https://github.com/Broadcom/stblinux-4.9 | |
| 55 | ||
| 56 | and with a generic ARMv7 root file system. | |
| 57 | ||
| 58 | image.its: | |
| 59 | /dts-v1/; | |
| 60 | / { | |
| 61 | description = "BCM7445 FIT"; | |
| 62 | images { | |
| 63 | kernel@1 { | |
| 64 | description = "Linux kernel"; | |
| 65 | /* | |
| 66 | * This kernel image output format can be | |
| 67 | * generated with: | |
| 68 | * | |
| 69 | * make vmlinux | |
| 70 | * ${CROSS_COMPILE}objcopy -O binary -S vmlinux vmlinux.bin | |
| 71 | * gzip -9 vmlinux.bin | |
| 72 | * | |
| 73 | * For stblinux-3.14, the specific Broadcom | |
| 74 | * board type should be configured in the | |
| 75 | * kernel, for example CONFIG_BCM7445D0=y. | |
| 76 | */ | |
| 77 | data = /incbin/("<vmlinux.bin.gz>"); | |
| 78 | type = "kernel"; | |
| 79 | arch = "arm"; | |
| 80 | os = "linux"; | |
| 81 | compression = "gzip"; | |
| 82 | load = <0x8000>; | |
| 83 | entry = <0x8000>; | |
| 84 | hash@1 { | |
| 85 | algo = "sha256"; | |
| 86 | }; | |
| 87 | }; | |
| 88 | ramdisk@1 { | |
| 89 | description = "Initramfs root file system"; | |
| 90 | data = /incbin/("<initramfs.cpio.gz>"); | |
| 91 | type = "ramdisk"; | |
| 92 | arch = "arm"; | |
| 93 | os = "linux"; | |
| 94 | compression = "gzip"; | |
| 95 | /* | |
| 96 | * Set the environment variable initrd_high to | |
| 97 | * 0xffffffff, and set "load" and "entry" here | |
| 98 | * to 0x0 to keep initramfs in-place and to | |
| 99 | * accommodate stblinux bmem/CMA reservations. | |
| 100 | */ | |
| 101 | load = <0x0>; | |
| 102 | entry = <0x0>; | |
| 103 | hash@1 { | |
| 104 | algo = "sha256"; | |
| 105 | }; | |
| 106 | }; | |
| 107 | fdt@1 { | |
| 108 | description = "Device tree dumped from BOLT"; | |
| 109 | /* | |
| 110 | * This DTB should be similar to the | |
| 111 | * BOLT-generated device tree, after BOLT has | |
| 112 | * done its runtime modifications to it. For | |
| 113 | * example, it can be dumped from within | |
| 114 | * U-Boot (at ${fdtcontroladdr}), after BOLT | |
| 115 | * has loaded U-Boot. The result can be added | |
| 116 | * to the Linux source tree as a .dts file. | |
| 117 | * | |
| 118 | * To support modifications to the device tree | |
| 119 | * in-place in U-Boot, add to Linux's | |
| 120 | * arch/arm/boot/dts/Makefile: | |
| 121 | * | |
| 122 | * DTC_FLAGS ?= -p 4096 | |
| 123 | * | |
| 124 | * This will leave some padding in the DTB and | |
| 125 | * thus reserve room for node additions. | |
| 126 | * | |
| 127 | * Also, set the environment variable fdt_high | |
| 128 | * to 0xffffffff to keep the DTB in-place and | |
| 129 | * to accommodate stblinux bmem/CMA | |
| 130 | * reservations. | |
| 131 | */ | |
| 132 | data = /incbin/("<bolt-<version>.dtb"); | |
| 133 | type = "flat_dt"; | |
| 134 | arch = "arm"; | |
| 135 | compression = "none"; | |
| 136 | hash@1 { | |
| 137 | algo = "sha256"; | |
| 138 | }; | |
| 139 | }; | |
| 140 | }; | |
| 141 | configurations { | |
| 142 | default = "conf@bcm7445"; | |
| 143 | conf@bcm7445 { | |
| 144 | description = "BCM7445 configuration"; | |
| 145 | kernel = "kernel@1"; | |
| 146 | ramdisk = "ramdisk@1"; | |
| 147 | fdt = "fdt@1"; | |
| 148 | }; | |
| 149 | }; | |
| 150 | }; |