mirror of
https://github.com/AsahiLinux/u-boot
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107 lines
4.4 KiB
Text
107 lines
4.4 KiB
Text
Board: Nokia RX-51 aka N900
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This board definition results in a u-boot.bin which can be chainloaded
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from NOLO in qemu or on a real N900. It does very little hardware config
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because NOLO has already configured the board. Only needed is enabling
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internal eMMC memory via twl4030 regulator which is not enabled by NOLO.
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NOLO is expecting a kernel image and will treat any image it finds in
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onenand as such. This u-boot is intended to be flashed to the N900 like
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a kernel. In order to transparently boot the original kernel, it will be
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appended to u-boot.bin at 0x40000. NOLO will load the entire image into
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(random) memory and execute u-boot, which saves hw revision, boot reason
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and boot mode ATAGs set by NOLO. Then the bootscripts will attempt to load
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uImage or boot.scr from a fat, ext2/ext3 or ext4 filesystem in external
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SD card or internal eMMC memory. If this fails or keyboard is closed then
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the appended kernel image will be booted using some generated and some
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stored ATAGs (see boot order).
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For generating combined image of u-boot and kernel there is a simple script
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called u-boot-gen-combined. It is available in following repository:
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https://github.com/pali/u-boot-maemo
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There is support for hardware watchdog. Hardware watchdog is started by
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NOLO so u-boot must kick watchdog to prevent reboot device (but not very
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often, max every 2 seconds). There is also support for framebuffer display
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output with ANSI escape codes and the N900 HW keyboard input. USB tty works
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but is disabled because it prevents the current Maemo kernel from booting.
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When U-Boot is starting it enable IBE bit in Auxiliary Control Register,
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which is needed for Thumb-2 ISA support. It is workaround for errata 430973.
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Default boot order:
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* 0. if keyboard is closed boot automatically attached kernel image
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* 1. try boot from external SD card
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* 2. try boot from internal eMMC memory
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* 3. try boot from attached kernel image
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Boot from SD or eMMC in this order:
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* 1.
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* 1.1 find boot.scr on first fat partition
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* 1.2 find uImage on first fat partition
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* 1.3 same order for 2. - 4. fat partition
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* 2. same as 1. but for ext2/3 partition
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* 3. same as 1. but for ext4 partition
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Available additional commands/variables:
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* run sercon - Use serial port for control
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* run usbcon - Use usbtty for control
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* run vgacon - Use framebuffer and HW keyboard for control (default)
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* run sdboot - Boot from external SD card (see boot order)
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* run emmcboot - Boot from internal eMMC memory (see boot order)
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* run attachboot - Boot attached kernel image (attached to U-Boot binary)
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* run scriptload - Load boot script ${mmcscriptfile}
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* run scriptboot - Run loaded boot script
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* run kernload - Load kernel image ${mmckernfile}
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* run initrdload - Load initrd image ${mmcinitrdfile}
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* run kernboot - Boot loaded kernel image
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* run kerninitrdboot - Boot loaded kernel image with loaded initrd image
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* run trymmcscriptboot - Try to load and boot script ${mmcscriptfile}
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* run trymmckernboot - Try to load and boot kernel image ${mmckernfile}
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* run trymmckerninitrdboot - Try to load and boot kernel image ${mmckernfile}
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with initrd image ${mmcinitrdfile}
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Additional variables for loading files from mmc:
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* mmc ${mmcnum} (0 - external, 1 - internal)
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* partition number ${mmcpart} (1 - 4)
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* parition type ${mmctype} (fat, ext2, ext4)
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Additional variables for booting kernel:
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* setup_omap_atag - Add OMAP table into atags structure (needs maemo kernel)
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* setup_console_atag - Enable serial console in OMAP table
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* setup_boot_reason_atag - Change boot reason in OMAP table
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* setup_boot_mode_atag - Change boot mode in OMAP table
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Variable setup_omap_atag is automatically set when booting attached kernel.
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When variable setup_omap_atag is set, variable setup_console_atag is unset
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and u-boot standard output is set to serial then setup_console_atag is
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automatically set to 1. So output from Maemo kernel would go to serial port.
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USB TTY:
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Maemo kernel 2.6.28 will crash if u-boot enable usb tty. So USB TTY is disabled.
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For enabling USB TTY just add this line to file include/configs/nokia_rx51.h
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#define CONFIG_USB_TTY
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UBIFS support:
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UBIFS support is disabled, because U-Boot image is too big and cannot be
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flashed with attached zImage to RX-51 kernel nand area. For enabling UBIFS
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support add following lines into file configs/nokia_rx51_defconfig
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CONFIG_CMD_UBI=y
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CONFIG_CMD_UBIFS=y
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CONFIG_MTD_UBI_FASTMAP=y
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CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT=1
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