forked from OERV-BSP/u-boot
7187408553
Switch boards that use CFG_PRAM to TEGRA_PRAM. Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
113 lines
3.4 KiB
ReStructuredText
113 lines
3.4 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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U-Boot for the Xiaomi Mi Pad tablet
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===================================
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``DISCLAMER!`` Moving your Xiaomi Mi Pad to use U-Boot assumes replacement
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of the vendor bootloader. Vendor Android firmwares will no longer be able
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to run on the device. This replacement IS reversible.
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Quick Start
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-----------
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- Build U-Boot
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- Boot U-Boot
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- Process and flash U-Boot
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- Boot Linux
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- Self Upgrading
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- Chainload configuration
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Build U-Boot
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------------
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.. code-block:: bash
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$ export CROSS_COMPILE=arm-none-eabi-
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$ make mocha_defconfig
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$ make
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After the build succeeds, you will obtain the final ``u-boot-dtb-tegra.bin``
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image, ready for booting or further processing.
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Boot U-Boot
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-----------
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Existing tegrarcm loader can be used to pre-load U-Boot you have build
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into RAM and basically perform a tethered cold-boot.
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.. code-block:: bash
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$ tegrarcm --bct mocha.bct --bootloader u-boot-dtb-tegra.bin --loadaddr 0x80108000
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U-Boot will try to load Linux kernel and if fails, it will turn the
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tablet off. While pre-loading U-Boot, hold the ``volume down`` button
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which will trigger the bootmenu.
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Process and flash U-Boot
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------------------------
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``DISCLAMER!`` All questions related to the re-crypt work should be asked
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in re-crypt repo issues. NOT HERE!
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re-crypt is a tool that processes the ``u-boot-dtb-tegra.bin`` binary into
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form usable by device. This process is required only on the first
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installation or to recover the device in case of a failed update.
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.. code-block:: bash
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$ git clone https://gitlab.com/grate-driver/re-crypt.git
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$ cd re-crypt # place your u-boot-dtb-tegra.bin here
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$ ./re-crypt.py --dev mocha
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The script will produce ``bct.img`` and ``ebt.img`` ready to flash.
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Permanent installation can be performed by pre-loading just built U-Boot
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into RAM via tegrarcm. While pre-loading U-Boot, hold the ``volume down``
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button which will trigger the bootmenu. There, select ``fastboot`` using
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the volume and power buttons.
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After, on host PC, do:
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.. code-block:: bash
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$ fastboot flash 0.1 bct.img
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$ fastboot flash 0.2 ebt.img
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$ fastboot reboot
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Device will reboot.
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Boot Linux
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----------
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To boot Linux, U-Boot will look for an ``extlinux.conf`` on MicroSD and then on
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eMMC. Additionally, if the ``volume down`` button is pressed while booting, the
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device will enter bootmenu. Bootmenu contains entries to mount MicroSD and eMMC
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as mass storage, fastboot, reboot, reboot RCM, poweroff, enter U-Boot console
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and update bootloader (check the next chapter).
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Flashing ``bct.img`` and ``ebt.img`` eliminates vendor restrictions on eMMC and
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allows the user to use/partition it in any way the user desires.
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Self Upgrading
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--------------
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Place your ``u-boot-dtb-tegra.bin`` on the first partition of the MicroSD card
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and insert it into the tablet. Enter bootmenu, choose update the bootloader
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option with the Power button and U-Boot should update itself. Once the process
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is completed, U-Boot will ask to press any button to reboot.
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Chainload configuration
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-----------------------
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To build U-Boot without SPL suitable for chainloading adjust mocha_defconfig:
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.. code-block::
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CONFIG_TEXT_BASE=0x80A00000
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CONFIG_SKIP_LOWLEVEL_INIT=y
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# CONFIG_OF_BOARD_SETUP is not set
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CONFIG_TEGRA_PRAM=y
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After the build succeeds, you will obtain the final ``u-boot-dtb.bin``
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file, ready for booting using vendor bootloader's fastboot or which can be
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further processed into a flashable image.
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