Documentation: zynqmp: add some documentation

Add at least some information how Barebox can be used on the ZynqMP and
what is required to create a bootable image.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Link: https://lore.barebox.org/20210624150054.1205422-8-m.tretter@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 40 insertions, 0 deletions

diff --git a/Documentation/boards/zynqmp.rst b/Documentation/boards/zynqmp.rst
new file mode 100644
index 0000000000..05d41c401d
--- /dev/null
+++ b/Documentation/boards/zynqmp.rst
@@ -0,0 +1,40 @@
+Xilinx ZynqMP Ultrascale+
+=========================
+
+Barebox has support as a second stage boot loader for the Xilinx ZynqMP
+Ultrascale+.
+
+Image creation
+--------------
+
+Currently, Barebox only supports booting as a second stage boot loader from an
+SD-card. It relies on the FSBL_ to initialize the base system including sdram
+setup and pin muxing.
+
+The ZynqMP defconfig supports the ZCU104 reference board. Use it to build the
+Barebox image::
+
+   make ARCH=arm64 zynqmp_defconfig
+   make ARCH=arm64
+
+.. note:: The resulting image ``images/barebox-zynqmp-zcu104.img`` is **not** an image
+  that can directly be booted on the ZynqMP.
+
+For a bootable BOOT.BIN image, you also need to build the FSBL_ and a ZynqMP
+TF-A. Prepare these separately using the respective instructions.
+
+Use bootgen_ or ``mkimage -T zynqmpbif`` from the U-boot tools to build the
+final BOOT.BIN image that can be loaded by the ROM code. Check the
+instructions for these tools how to prepare the BOOT.BIN image.
+
+Create a FAT partition as the first partition of the SD card and copy the
+produced BOOT.BIN into this partition.
+
+.. _FSBL: `https://github.com/Xilinx/embeddedsw/`
+.. _bootgen: `https://github.com/Xilinx/bootgen`
+
+Booting Barebox
+---------------
+
+The FSBL loads the TF-A and Barebox, jumps to the TF-A, which will then return
+to Barebox. Afterwards, you can use Barebox as usual.