1Board: Nokia RX-51 aka N900 2 3This board definition results in a u-boot.bin which can be chainloaded 4from NOLO in qemu or on a real N900. It does very little hardware config 5because NOLO has already configured the board. Only needed is enabling 6internal eMMC memory via twl4030 regulator which is not enabled by NOLO. 7 8NOLO is expecting a kernel image and will treat any image it finds in 9onenand as such. This u-boot is intended to be flashed to the N900 like 10a kernel. In order to transparently boot the original kernel, it will be 11appended to u-boot.bin at 0x40000. NOLO will load the entire image into 12(random) memory and execute u-boot, which saves hw revision, boot reason 13and boot mode ATAGs set by NOLO. Then the bootscripts will attempt to load 14uImage, zImage or boot.scr from a fat or ext2/3/4 filesystem on external 15SD card or internal eMMC memory. If this fails or keyboard is closed then 16the appended kernel image will be booted using some generated and some 17stored ATAGs (see boot order). 18 19For generating combined image of u-boot and kernel (either in uImage or zImage 20format) there is a simple script called u-boot-gen-combined. It is available in 21following repository: 22 23 https://github.com/pali/u-boot-maemo 24 25There is support for hardware watchdog. Hardware watchdog is started by 26NOLO so u-boot must kick watchdog to prevent reboot device (but not very 27often, max every 2 seconds). There is also support for framebuffer display 28output with ANSI escape codes and the N900 HW keyboard input. 29 30When U-Boot is starting it enable IBE bit in Auxiliary Control Register, 31which is needed for Thumb-2 ISA support. It is workaround for errata 430973. 32 33Default boot order: 34 35 * 0. if keyboard is closed boot automatically attached kernel image 36 * 1. try boot from external SD card 37 * 2. try boot from internal eMMC memory 38 * 3. try boot from attached kernel image 39 40Boot from SD or eMMC in this order: 41 42 * 1. 43 * 1.1 find boot.scr on first fat partition 44 * 1.2 find uImage on first fat partition 45 * 1.3 find zImage on first fat partition 46 * 1.4 same order for 2. - 4. fat partition 47 * 2. same as 1. but for ext2/3 partition 48 * 3. same as 1. but for ext4 partition 49 50 51Available additional commands/variables: 52 53 * run sdboot - Boot from external SD card (see boot order) 54 * run emmcboot - Boot from internal eMMC memory (see boot order) 55 * run attachboot - Boot attached kernel image (attached to U-Boot binary) 56 57 * run scriptload - Load boot script ${mmcscriptfile} 58 * run scriptboot - Run loaded boot script 59 * run kernload - Load kernel image ${mmckernfile} 60 * run initrdload - Load initrd image ${mmcinitrdfile} 61 * run kernboot - Boot loaded kernel image 62 * run kerninitrdboot - Boot loaded kernel image with loaded initrd image 63 64 * run trymmcscriptboot - Try to load and boot script ${mmcscriptfile} 65 * run trymmckernboot - Try to load and boot kernel image ${mmckernfile} 66 * run trymmckerninitrdboot - Try to load and boot kernel image ${mmckernfile} 67 with initrd image ${mmcinitrdfile} 68 69Additional variables for loading files from mmc: 70 71 * mmc ${mmcnum} (0 - external, 1 - internal) 72 * partition number ${mmcpart} (1 - 4) 73 * parition type ${mmctype} (fat, ext2, ext4) 74 75Additional variables for booting kernel: 76 77 * setup_omap_atag - Add OMAP table into atags structure (needs maemo kernel) 78 * setup_console_atag - Enable serial console in OMAP table 79 * setup_boot_reason_atag - Change boot reason in OMAP table 80 * setup_boot_mode_atag - Change boot mode in OMAP table 81 82 Variable setup_omap_atag is automatically set when booting attached kernel. 83 When variable setup_omap_atag is set, variable setup_console_atag is unset 84 and u-boot standard output is set to serial then setup_console_atag is 85 automatically set to 1. So output from Maemo kernel would go to serial port. 86 87UBIFS support: 88 89 UBIFS support is disabled, because U-Boot image is too big and cannot be 90 flashed with attached zImage to RX-51 kernel nand area. For enabling UBIFS 91 support add following lines into file configs/nokia_rx51_defconfig 92 93 CONFIG_CMD_UBI=y 94 CONFIG_CMD_UBIFS=y 95 CONFIG_MTD_UBI_FASTMAP=y 96 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT=1 97