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docs/system/arm: xlnx-versal-virt: BBRAM and eFUSE Usage 

Add BBRAM and eFUSE usage to the Xilinx Versal Virt board
document.

Signed-off-by: Tong Ho <tong.ho@xilinx.com>
Message-id: 20210917052400.1249094-10-tong.ho@xilinx.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
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Tong Ho 2021-09-16 22:24:00 -07:00 committed by Peter Maydell
parent db1264df32
commit 09e010aede
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docs/system/arm/xlnx-versal-virt.rst
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@ -32,6 +32,8 @@ Implemented devices:
- OCM (256KB of On Chip Memory)
- XRAM (4MB of on chip Accelerator RAM)
- DDR memory
- BBRAM (36 bytes of Battery-backed RAM)
- eFUSE (3072 bytes of one-time field-programmable bit array)
QEMU does not yet model any other devices, including the PL and the AI Engine.
@ -175,3 +177,50 @@ Run the following at the U-Boot prompt:
fdt set /chosen/dom0 reg <0x00000000 0x40000000 0x0 0x03100000>
booti 30000000 - 20000000
BBRAM File Backend
""""""""""""""""""
BBRAM can have an optional file backend, which must be a seekable
binary file with a size of 36 bytes or larger. A file with all
binary 0s is a 'blank'.
To add a file-backend for the BBRAM:
.. code-block:: bash
-drive if=pflash,index=0,file=versal-bbram.bin,format=raw
To use a different index value, N, from default of 0, add:
.. code-block:: bash
-global xlnx,bbram-ctrl.drive-index=N
eFUSE File Backend
""""""""""""""""""
eFUSE can have an optional file backend, which must be a seekable
binary file with a size of 3072 bytes or larger. A file with all
binary 0s is a 'blank'.
To add a file-backend for the eFUSE:
.. code-block:: bash
-drive if=pflash,index=1,file=versal-efuse.bin,format=raw
To use a different index value, N, from default of 1, add:
.. code-block:: bash
-global xlnx,efuse.drive-index=N
.. warning::
In actual physical Versal, BBRAM and eFUSE contain sensitive data.
The QEMU device models do **not** encrypt nor obfuscate any data
when holding them in models' memory or when writing them to their
file backends.
Thus, a file backend should be used with caution, and 'format=luks'
is highly recommended (albeit with usage complexity).
Better yet, do not use actual product data when running guest image
on this Xilinx Versal Virt board.