9c2d4057e1
Add example command how to compile U-Boot and add new documentation section describing how to enable early debug UART and verbose log output for N900. Signed-off-by: Pali Rohár <pali@kernel.org>
251 lines
9.2 KiB
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251 lines
9.2 KiB
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.. SPDX-License-Identifier: GPL-2.0+
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Nokia RX-51 aka N900
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====================
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The ``nokia_rx51_defconfig`` configuration file results in a ``u-boot.bin``
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which can be chainloaded by the Nokia second stage bootloader (NOLO) in QEMU or
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on a real N900. It does very little hardware configuration because NOLO has
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already configured the board. It is only needed to enable the internal eMMC
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memory via the twl4030 regulator which is not enabled by NOLO.
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.. code-block:: bash
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make CROSS_COMPILE=arm-linux-gnueabi- nokia_rx51_defconfig u-boot.bin
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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 hardware 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``, ``zImage`` or ``boot.scr`` file from a FAT or ext2/3/4 filesystem
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on external SD card or internal eMMC memory. If this fails or keyboard is
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closed then the appended kernel image will be booted using some generated
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and some stored ATAGs (see boot order).
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For generating combined image of U-Boot and kernel (either in uImage or zImage
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format) there is a simple script called ``u-boot-gen-combined``. It is available
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in following repository: https://github.com/pali/u-boot-maemo.
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To generate the ``combined.bin`` image from ``u-boot.bin`` and ``kernel.bin``
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(in either uImage or zImage format) use:
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.. code-block:: bash
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sh u-boot-gen-combined u-boot.bin kernel.bin combined.bin
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The original Maemo Fremantle PR1.3 zImage kernel binary is available at:
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http://repository.maemo.org/pool/maemo5.0/free/k/kernel/kernel_2.6.28-20103103+0m5_armel.deb
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To unpack it (from DEB/AR, TAR and FIASCO) execute the following commands:
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.. code-block:: bash
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ar x kernel_2.6.28-20103103+0m5_armel.deb data.tar.gz
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tar -O -xf data.tar.gz ./boot/zImage-2.6.28-20103103+0m5.fiasco > kernel_2.6.28-20103103+0m5.fiasco
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0xFFFF -M kernel_2.6.28-20103103+0m5.fiasco -u
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The flashed image must start with a 2 KiB ``NOLO!img`` header which contains
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size of the image. The header consists of the bytes
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``NOLO!img\x02\x00\x00\x00\x00\x00\x00\x00`` followed by the 4 byte little
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endian size of the image. The rest of the 2 KiB header just contains zero bytes.
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The Nokia proprietary flasher and also the open source 0xFFFF flasher
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automatically prepend the required ``NOLO!img`` header and both applications
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expect that the image does not contain a ``NOLO!img`` header. Adding a
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``NOLO!img`` header is required only in case of using the ``nandwrite`` tool for
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flashing.
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The open source 0xFFFF flasher is available in the following repository:
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https://github.com/pali/0xFFFF
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It is possible to load ``u-boot.bin`` via USB to the N900 RAM and boot it
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without needing to flash it. This is done via 0xFFFF running on the host PC:
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.. code-block:: bash
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0xFFFF -m u-boot.bin -l -b
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0xFFFF also supports flashing a kernel image either via USB or directly on
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N900 device. Flashing u-boot/kernel/combined image is done as:
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.. code-block:: bash
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0xFFFF -m combined.bin -f
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Via 0xFFFF it is also possible to generate a standard flashable image in
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Nokia FIASCO format which contains metadata information like device
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identification (RX-51) and version string (v2021.04):
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.. code-block:: bash
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0xFFFF -m RX-51:v2021.04:kernel:u-boot.bin -g u-boot.fiasco
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There is support for the hardware watchdog. The hardware watchdog is started by
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NOLO so U-Boot must reset the watchdog to prevent rebooting the device (but not
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very often, max every 2 seconds). There is also support for framebuffer display
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output with ANSI escape codes and the N900 hardware keyboard input.
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When U-Boot is starting it sets the IBE bit in the Auxiliary Control Register,
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which is needed for Thumb-2 ISA support. This is a workaround for erratum
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430973.
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Default boot order
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------------------
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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. boot from FAT partition
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a. find ``boot.scr`` on first FAT partition
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b. find ``uImage`` on first FAT partition
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c. find ``zImage`` on first FAT partition
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d. same order for 2nd - 4th FAT partition
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2. same as 1. but for ext2/3/4 partition
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Available additional commands/variables
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---------------------------------------
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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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\
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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 ``${mmcinitrdfile}``
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* run kernboot - Boot loaded kernel image
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* run kerninitrdboot - Boot loaded kernel image with loaded initrd image
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\
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* run trymmcscriptboot - Try to load and boot script ``${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 ``${mmcinitrdfile}``
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Additional variables for loading files from mmc
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-----------------------------------------------
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* mmc ``${mmcnum}`` (0 - external, 1 - internal)
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* partition number ``${mmcpart}`` (1 - 4)
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* partition type ``${mmctype}`` (fat, ext2, ext4; ext2 is just alias for ext4)
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Additional variables for booting a kernel
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-----------------------------------------
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* ``setup_omap_atag`` - Add OMAP table into atags structure (needed for 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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UBIFS support
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-------------
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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 kernel image to RX-51 kernel nand area. For enabling
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UBIFS 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_BEB_LIMIT=10
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Early output
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------------
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Early U-Boot output can be enabled on serial console by adding following lines
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into file ``configs/nokia_rx51_defconfig``::
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CONFIG_DEBUG_UART=y
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CONFIG_DEBUG_UART_OMAP=y
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CONFIG_DEBUG_UART_SHIFT=2
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CONFIG_DEBUG_UART_BASE=0x49020000
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CONFIG_DEBUG_UART_CLOCK=48000000
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Note that early output is not available on USB tty console.
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Verbose debug output
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--------------------
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Verbose debug output with maximal log level can be enabled by adding following
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lines into file ``configs/nokia_rx51_defconfig``::
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CONFIG_DM_DEBUG=y
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CONFIG_LOG=y
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CONFIG_LOGLEVEL=9
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CONFIG_LOG_MAX_LEVEL=9
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CONFIG_LOG_DEFAULT_LEVEL=9
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And compiling U-Boot by additional make parameter ``KCPPFLAGS=-DLOG_DEBUG``.
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Run in QEMU
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-----------
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Download and compile Linaro version of qemu which contains ``n900`` qemu
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machine. Source code is available in qemu-linaro git repository and the
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last working version is at commit 8f8d8e0796efe1a6f34cdd83fb798f3c41217ec1.
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Use following commands to compile ``qemu-system-arm`` binary with ``n900``
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qemu machine support:
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.. code-block:: bash
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git clone https://git.linaro.org/qemu/qemu-linaro.git
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cd qemu-linaro
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git checkout 8f8d8e0796efe1a6f34cdd83fb798f3c41217ec1
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./configure --enable-system --target-list=arm-softmmu --disable-werror
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make -j4
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cd ..
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ln -s qemu-linaro/arm-softmmu/qemu-system-arm .
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Using ``n900`` qemu machine requires proprietary Nokia qemu ``qflasher`` tool
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(in reality it is just generator of qemu MTD images) with first stage images
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(``xloader-qemu.bin`` and ``secondary-qemu.bin``), similar what is required
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on the real HW. License of flasher and images allows non-commercial
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redistribution and it is available at maemo.org website:
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.. code-block:: bash
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wget -c http://repository.maemo.org/qemu-n900/qemu-n900.tar.gz
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tar -xf qemu-n900.tar.gz
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To generate qemu bootable MTD image ``mtd.img`` from U-Boot binary
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``u-boot.bin`` and unpacked first stage images, run following command:
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.. code-block:: bash
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./qflasher -v -x xloader-qemu.bin -s secondary-qemu.bin -k u-boot.bin -m rx51 -o mtd.img
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Instead of ``u-boot.bin`` binary it is possible to also used combined
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U-Boot + kernel binary ``combined.bin``.
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Finally, to boot ``mtd.img`` with graphics display and keyboard with optional
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serial console on current terminal, run:
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.. code-block:: bash
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./qemu-system-arm -M n900 -mtdblock mtd.img -serial /dev/tty
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Additionally it is possible to emulate also eMMC and uSD card by appending
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qemu ``-sd`` arguments:
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.. code-block:: bash
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./qemu-system-arm -M n900 -mtdblock mtd.img -sd emmc.img -sd sd.img -serial /dev/tty
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For more examples, look into the ``test/nokia_rx51_test.sh`` CI testing script.
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