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48571ff0 SG |
1 | Summary |
2 | ======= | |
3 | The README is for the boot procedure used for TI's OMAP-L138 based | |
4 | hawkboard. The hawkboard comes with a 128MiB Nand flash and a 128MiB | |
5 | DDR SDRAM along with a host of other controllers. | |
6 | ||
7 | The hawkboard is booted in three stages. The initial bootloader which | |
8 | executes upon reset is the Rom Boot Loader(RBL) which sits in the | |
9 | internal ROM of the omap. The RBL initialises the memory and the nand | |
10 | controller, and copies the image stored at a predefined location(block | |
11 | 1) of the nand flash. The image loaded by the RBL to the memory is the | |
12 | AIS signed nand_spl image. This, in turns copies the u-boot binary | |
13 | from the nand flash to the memory and jumps to the u-boot entry point. | |
14 | ||
15 | AIS is an image format defined by TI for the images that are to be | |
16 | loaded to memory by the RBL. The image is divided into a series of | |
17 | sections and the image's entry point is specified. Each section comes | |
18 | with meta data like the target address the section is to be copied to | |
19 | and the size of the section, which is used by the RBL to load the | |
20 | image. At the end of the image the RBL jumps to the image entry | |
21 | point. | |
22 | ||
23 | The secondary stage bootloader(nand_spl) which is loaded by the RBL | |
24 | then loads the u-boot from a predefined location in the nand to the | |
25 | memory and jumps to the u-boot entry point. | |
26 | ||
27 | The reason a secondary stage bootloader is used is because the ECC | |
28 | layout expected by the RBL is not the same as that used by | |
29 | u-boot/linux. This also implies that for flashing the nand_spl image, | |
30 | we need to use the u-boot which uses the ECC layout expected by the | |
31 | RBL[1]. Booting u-boot over UART(UART boot) is explained here[2]. | |
32 | ||
33 | ||
34 | Compilation | |
35 | =========== | |
36 | Three images might be needed | |
37 | ||
38 | * nand_spl - This is the secondary bootloader which boots the u-boot | |
39 | binary. | |
40 | ||
41 | hawkboard_nand_config | |
42 | ||
43 | The nand_spl ELF gets generated under nand_spl/u-boot-spl. This | |
44 | needs to be processed with the AISGen tool for generating the AIS | |
45 | signed image to be flashed. Steps for generating the AIS image are | |
46 | explained here[3]. | |
47 | ||
48 | * u-boot binary - This is the image flashed to the nand and copied to | |
49 | the memory by the nand_spl. | |
50 | ||
51 | hawkboard_config | |
52 | ||
53 | * u-boot for uart boot - This is same as the u-boot binary generated | |
54 | above, with the sole difference of the CONFIG_SYS_TEXT_BASE being | |
55 | 0xc1080000, as expected by the RBL. | |
56 | ||
57 | hawkboard_uart_config | |
58 | ||
59 | ||
60 | Flashing the images to Nand | |
61 | =========================== | |
62 | The nand_spl AIS image needs to be flashed to the block 1 of the | |
63 | Nand flash, as that is the location the RBL expects the image[4]. For | |
64 | flashing the nand_spl, boot over the u-boot specified in [1], and | |
65 | flash the image | |
66 | ||
67 | => tftpboot 0xc0700000 <nand_spl_ais.bin> | |
68 | => nand erase 0x20000 0x20000 | |
69 | => nand write.e 0xc0700000 0x20000 <nand_spl_size> | |
70 | ||
71 | The u-boot binary is flashed at location 0xe0000(block 6) of the nand | |
72 | flash. The nand_spl loader expects the u-boot at this location. For | |
73 | flashing the u-boot binary | |
74 | ||
75 | => tftpboot 0xc0700000 u-boot.bin | |
76 | => nand erase 0xe0000 0x40000 | |
77 | => nand write.e 0xc0700000 0xe0000 <u-boot-size> | |
78 | ||
79 | ||
80 | Links | |
81 | ===== | |
82 | ||
83 | [1] | |
84 | http://code.google.com/p/hawkboard/downloads/detail?name=u-boot_uart_ais_v1.bin | |
85 | ||
86 | [2] | |
87 | http://elinux.org/Hawkboard#Booting_u-boot_over_UART | |
88 | ||
89 | [3] | |
90 | http://elinux.org/Hawkboard#Signing_u-boot_for_UART_boot | |
91 | ||
92 | [4] | |
93 | http://processors.wiki.ti.com/index.php/RBL_UBL_and_host_program#RBL_booting_from_NAND_and_ECC.2FBad_blocks |