board: asus: transformer: add ASUS Transformer T30 family support

The ASUS Transformer T30 family are 2-in-1 detachable tablets
and AiO developed by ASUS that run the Android operating system
(TF600T runs Windows RT and P1801-T runs Android and Windows).
The T30 Transformers feature a 10.1-inch display (apart P1801-T),
an Nvidia Tegra 3 quad-core chip, 1/2 GB of RAM, and 16/32 GB of
storage. Transformers board derives from Nvidia Cardhu development
board.

This patch brings support for 7 known Transformer devices:
- ASUS Transformer Prime TF201
- ASUS Transformer Pad TF300T/TF300TG/TF300TL
- ASUS VivoTab RT TF600T (Windows RT based)
- ASUS Transformer Infinity TF700T
- ASUS Portable AiO P1801-T

Tested-by: Andreas Westman Dorcsak <[email protected]> # all devices
Signed-off-by: Svyatoslav Ryhel <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>

3 files changed, 126 insertions, 0 deletions

diff --git a/doc/board/asus/index.rst b/doc/board/asus/index.rst
new file mode 100644
index 00000000000..c59571c8b3a
--- /dev/null
+++ b/doc/board/asus/index.rst
@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+ASUS
+====
+
+.. toctree::
+   :maxdepth: 2
+
+   transformer_t30
diff --git a/doc/board/asus/transformer_t30.rst b/doc/board/asus/transformer_t30.rst
new file mode 100644
index 00000000000..b6b61015409
--- /dev/null
+++ b/doc/board/asus/transformer_t30.rst
@@ -0,0 +1,116 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+U-Boot for the ASUS Transformer device family
+=============================================
+
+``DISCLAMER!`` Moving your ASUS Transformer to use U-Boot
+assumes replacement of the vendor ASUS bootloader. Vendor
+android firmwares will no longer be able to run on the device.
+This replacement IS reversible.
+
+Quick Start
+-----------
+
+- Build U-Boot
+- Pack U-Boot into repart-block
+- Flash repart-block into the eMMC
+- Flash repart-block into TF600T SPI flash
+- Boot
+- Self Upgrading
+
+Build U-Boot
+------------
+
+Device support is implemented by applying config fragment
+to a generic board defconfig. Valid fragments are ``tf201.config``,
+``tf300t.config``, ``tf300tg.config``, ``tf300tl.config``,
+``tf700t.config``, ``tf600t.config`` and ``p1801-t.config``.
+
+.. code-block:: bash
+
+    $ export CROSS_COMPILE=arm-linux-gnueabi-
+    $ make transformer_t30_defconfig tf201.config # For TF201
+    $ make
+
+After the build succeeds, you will obtain the final ``u-boot-dtb-tegra.bin``
+image, ready for flashing (but check the next section for additional
+adjustments).
+
+Pack U-Boot into repar-block
+----------------------------
+
+``DISCLAMER!`` All questions related to re-crypt work should be asked
+in re-crypt repo issues. NOT HERE!
+
+re-crypt is a small script which packs ``u-boot-dtb-tegra.bin`` in
+form usable by device. This process is required only on the first
+installation or to recover the device in case of a failed update.
+You need to know your tablet's individual SBK to continue.
+
+.. code-block:: bash
+
+    $ git clone https://github.com/clamor-s/re-crypt.git
+    $ cd re-crypt # place your u-boot-dtb-regra.bin here
+    $ ./re-crypt.sh -d tf201 -k deadbeefdeadc0dedeadd00dfee1dead
+
+Script will produce you a `repart-block.bin` ready to flash.
+
+Flash repart-block into the eMMC
+--------------------------------
+
+``DISCLAMER!`` All questions related to NvFlash should be asked
+in the proper place. NOT HERE! Flashing repart-block will erase
+all your eMMC, so make a backup before!
+
+``repart-block.bin`` contains BCT and bootloader in encrypted state
+in form which can just be written RAW at the start of eMMC.
+
+.. code-block:: bash
+
+    $ wheelie --blob blob.bin
+    $ nvflash --resume --rawdevicewrite 0 1024 repart-block.bin
+
+Flash repart-block into TF600T SPI flash
+----------------------------------------
+
+Unlike other transformers TF600T uses separate 4 MB SPI flash which
+contains all data required for boot. It is flashed from within u-boot
+itself preloaded into RAM using fusee gelee. After creating your
+``repart-block.bin`` you have to place it on a 1st partition of microSD
+card formated in fat. Then insert this microSD card into your tablet
+and boot it using fusee gelee and u-boot which was included into
+repart-block.bin, while booting you must hold volume down button.
+Process should take less then a minute, if everything goes correct,
+on microSD will appear ``spi-flash-backup.bin`` file, which is dump of
+your spi flash content and can be used to restore UEFI, do not loose it,
+tablet will power itself off.
+
+Self-updating of u-boot is performed by placing ``u-boot-dtb-tegra.bin``
+on 1st partition of microSD, inserting it into tablet and booting with
+pressed volume down button.
+
+Boot
+----
+
+After flashing ``repart-block.bin`` the device should reboot and turn
+itself off. This is normal behavior if no boot configuration is
+found.
+
+To boot Linux, U-Boot will look for an ``extlinux.conf`` on MicroSD
+and then on eMMC. Additionally if Volume Down button is pressed
+while booting device will enter bootmenu. Bootmenu contains entries
+to mount MicroSD and eMMC as mass storage, fastboot, reboot, reboot
+RCM, poweroff, enter U-Boot console and update bootloader (check next
+chapter).
+
+Flashing ``repart-block.bin`` eliminates vendor restriction on eMMC
+and allows the user to use/partition it in any way the user desires.
+
+Self Upgrading
+--------------
+
+Place your ``u-boot-dtb-tegra.bin`` on the first partition of the
+MicroSD card and insert it into the tablet. Enter bootmenu, choose
+update bootloader option with Power button and U-Boot should update
+itself. Once the process is completed, U-Boot will ask to press any
+button to reboot.
diff --git a/doc/board/index.rst b/doc/board/index.rst
index 9ef25b10915..d28d8e18745 100644
--- a/doc/board/index.rst
+++ b/doc/board/index.rst
@@ -14,6 +14,7 @@ Board-specific doc
    anbernic/index
    apple/index
    armltd/index
+   asus/index
    atmel/index
    beacon/index
    broadcom/index