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d0ed9b1081
This converts the semihosting readme to rST. I have tried to make only cosmetic changes, but I did fix up the first link (which was broken). Signed-off-by: Sean Anderson <sean.anderson@seco.com>
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1.8 KiB
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44 lines
1.8 KiB
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.. SPDX-License-Identifier: GPL-2.0+
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.. Copyright 2014 Broadcom Corporation.
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Semihosting
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===========
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Semihosting is ARM's way of having a real or virtual target communicate
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with a host or host debugger for basic operations such as file I/O,
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console I/O, etc. Please see `Arm's semihosting documentation
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<https://developer.arm.com/documentation/100863/latest/>`_ for more
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information.
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For developing on armv8 virtual fastmodel platforms, semihosting is a
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valuable tool since it allows access to image/configuration files before
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eMMC or other NV media are available.
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There are two main ARM virtual Fixed Virtual Platform (FVP) models,
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`Versatile Express (VE) FVP and BASE FVP
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<http://www.arm.com/products/tools/models/fast-models/foundation-model.php>`_.
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The initial vexpress64 u-boot board created here runs on the VE virtual
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platform using the license-free Foundation_v8 simulator. Fortunately,
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the Foundation_v8 simulator also supports the BASE_FVP model which
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companies can purchase licenses for and contain much more functionality.
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So we can, in U-Boot, run either model by either using the VE FVP (default),
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or turning on ``CONFIG_BASE_FVP`` for the more full featured model.
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Rather than create a new armv8 board similar to ``armltd/vexpress64``, add
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semihosting calls to the existing one, enabled with ``CONFIG_SEMIHOSTING``
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and ``CONFIG_BASE_FVP`` both set. Also reuse the existing board config file
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vexpress_aemv8.h but differentiate the two models by the presence or
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absence of ``CONFIG_BASE_FVP``. This change is tested and works on both the
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Foundation and Base fastmodel simulators.
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Loading files
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-------------
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The semihosting code adds a "hostfs"::
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smhload <image> <address> [env var]
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That will load an image from the host filesystem into RAM at the specified
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address and optionally store the load end address in the specified
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environment variable.
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