Nokia RX-51 aka N900¶
The nokia_rx51_defconfig
configuration file results in a u-boot.bin
which can be chainloaded by the Nokia second stage bootloader (NOLO) in QEMU or
on a real N900. It does very little hardware configuration because NOLO has
already configured the board. It is only needed to enable the internal eMMC
memory via the twl4030 regulator which is not enabled by NOLO.
NOLO is expecting a kernel image and will treat any image it finds in
OneNAND as such. This u-boot is intended to be flashed to the N900 like
a kernel. In order to transparently boot the original kernel, it will be
appended to u-boot.bin
at 0x40000. NOLO will load the entire image into
(random) memory and execute U-Boot, which saves hardware revision, boot reason
and boot mode ATAGs set by NOLO. Then the bootscripts will attempt to load
uImage
, zImage
or boot.scr
file from a FAT or ext2/3/4 filesystem
on external SD card or internal eMMC memory. If this fails or keyboard is
closed then the appended kernel image will be booted using some generated
and some stored ATAGs (see boot order).
For generating combined image of U-Boot and kernel (either in uImage or zImage
format) there is a simple script called u-boot-gen-combined
. It is available
in following repository: https://github.com/pali/u-boot-maemo.
To generate the combined.bin
image from u-boot.bin
and kernel.bin
(in either uImage or zImage format) use:
sh u-boot-gen-combined u-boot.bin kernel.bin combined.bin
The original Maemo Fremantle PR1.3 zImage kernel binary is available at: http://repository.maemo.org/pool/maemo5.0/free/k/kernel/kernel_2.6.28-20103103+0m5_armel.deb
To unpack it (from DEB/AR, TAR and FIASCO) execute the following commands:
ar x kernel_2.6.28-20103103+0m5_armel.deb data.tar.gz
tar -O -xf data.tar.gz ./boot/zImage-2.6.28-20103103+0m5.fiasco > kernel_2.6.28-20103103+0m5.fiasco
0xFFFF -M kernel_2.6.28-20103103+0m5.fiasco -u
The flashed image must start with a 2 KiB NOLO!img
header which contains
size of the image. The header consists of the bytes
NOLO!img\x02\x00\x00\x00\x00\x00\x00\x00
followed by the 4 byte little
endian size of the image. The rest of the 2 KiB header just contains zero bytes.
The Nokia proprietary flasher and also the open source 0xFFFF flasher
automatically prepend the required NOLO!img
header and both applications
expect that the image does not contain a NOLO!img
header. Adding a
NOLO!img
header is required only in case of using the nandwrite
tool for
flashing.
The open source 0xFFFF flasher is available in the following repository: https://github.com/pali/0xFFFF
It is possible to load u-boot.bin
via USB to the N900 RAM and boot it
without needing to flash it. This is done via 0xFFFF running on the host PC:
0xFFFF -m u-boot.bin -l -b
0xFFFF also supports flashing a kernel image either via USB or directly on N900 device. Flashing u-boot/kernel/combined image is done as:
0xFFFF -m combined.bin -f
Via 0xFFFF it is also possible to generate a standard flashable image in Nokia FIASCO format which contains metadata information like device identification (RX-51) and version string (v2021.04):
0xFFFF -m RX-51:v2021.04:kernel:u-boot.bin -g u-boot.fiasco
There is support for the hardware watchdog. The hardware watchdog is started by NOLO so U-Boot must reset the watchdog to prevent rebooting the device (but not very often, max every 2 seconds). There is also support for framebuffer display output with ANSI escape codes and the N900 hardware keyboard input.
When U-Boot is starting it sets the IBE bit in the Auxiliary Control Register, which is needed for Thumb-2 ISA support. This is a workaround for erratum 430973.
Default boot order¶
if keyboard is closed boot automatically attached kernel image
try boot from external SD card
try boot from internal eMMC memory
try boot from attached kernel image
Boot from SD or eMMC in this order:
boot from FAT partition
find
boot.scr
on first FAT partitionfind
uImage
on first FAT partitionfind
zImage
on first FAT partitionsame order for 2nd - 4th FAT partition
same as 1. but for ext2/3/4 partition
Available additional commands/variables¶
run sdboot - Boot from external SD card (see boot order)
run emmcboot - Boot from internal eMMC memory (see boot order)
run attachboot - Boot attached kernel image (attached to U-Boot binary)
run scriptload - Load boot script
${mmcscriptfile}
run scriptboot - Run loaded boot script
run kernload - Load kernel image
${mmckernfile}
run initrdload - Load initrd image
${mmcinitrdfile}
run kernboot - Boot loaded kernel image
run kerninitrdboot - Boot loaded kernel image with loaded initrd image
run trymmcscriptboot - Try to load and boot script
${mmcscriptfile}
run trymmckernboot - Try to load and boot kernel image
${mmckernfile}
run trymmckerninitrdboot - Try to load and boot kernel image
${mmckernfile}
with initrd image${mmcinitrdfile}
Additional variables for loading files from mmc¶
mmc
${mmcnum}
(0 - external, 1 - internal)partition number
${mmcpart}
(1 - 4)partition type
${mmctype}
(fat, ext2, ext4; ext2 is just alias for ext4)
Additional variables for booting a kernel¶
setup_omap_atag
- Add OMAP table into atags structure (needed for maemo kernel)setup_console_atag
- Enable serial console in OMAP tablesetup_boot_reason_atag
- Change boot reason in OMAP tablesetup_boot_mode_atag
- Change boot mode in OMAP table
Variable setup_omap_atag
is automatically set when booting attached kernel.
When variable setup_omap_atag
is set, variable setup_console_atag
is unset
and u-boot standard output is set to serial then setup_console_atag
is
automatically set to 1. So output from Maemo kernel would go to serial port.
UBIFS support¶
UBIFS support is disabled, because U-Boot image is too big and cannot be
flashed with attached kernel image to RX-51 kernel nand area. For enabling
UBIFS support add following lines into file configs/nokia_rx51_defconfig
:
CONFIG_CMD_UBI=y
CONFIG_CMD_UBIFS=y
CONFIG_MTD_UBI_FASTMAP=y
CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT=1
Run in QEMU¶
Download and compile Linaro version of qemu which contains n900
qemu
machine. Source code is available in qemu-linaro git repository and the
last working version is at commit 8f8d8e0796efe1a6f34cdd83fb798f3c41217ec1.
Use following commands to compile qemu-system-arm
binary with n900
qemu machine support:
git clone https://git.linaro.org/qemu/qemu-linaro.git
cd qemu-linaro
git checkout 8f8d8e0796efe1a6f34cdd83fb798f3c41217ec1
./configure --enable-system --target-list=arm-softmmu --disable-werror
make -j4
cd ..
ln -s qemu-linaro/arm-softmmu/qemu-system-arm .
Using n900
qemu machine requires proprietary Nokia qemu qflasher
tool
(in reality it is just generator of qemu MTD images) with first stage images
(xloader-qemu.bin
and secondary-qemu.bin
), similar what is required
on the real HW. License of flasher and images allows non-commercial
redistribution and it is available at maemo.org website:
wget -c http://repository.maemo.org/qemu-n900/qemu-n900.tar.gz
tar -xf qemu-n900.tar.gz
To generate qemu bootable MTD image mtd.img
from U-Boot binary
u-boot.bin
and unpacked first stage images, run following command:
./qflasher -v -x xloader-qemu.bin -s secondary-qemu.bin -k u-boot.bin -m rx51 -o mtd.img
Instead of u-boot.bin
binary it is possible to also used combined
U-Boot + kernel binary combined.bin
.
Finally, to boot mtd.img
with graphics display and keyboard with optional
serial console on current terminal, run:
./qemu-system-arm -M n900 -mtdblock mtd.img -serial /dev/tty
Additionally it is possible to emulate also eMMC and uSD card by appending
qemu -sd
arguments:
./qemu-system-arm -M n900 -mtdblock mtd.img -sd emmc.img -sd sd.img -serial /dev/tty
For more examples, look into the test/nokia_rx51_test.sh
CI testing script.