mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-21 02:33:07 +00:00
93c3d32970
This adds support for booting entirely from JTAG while using a
hard-coded RCW. With these steps, it is not necessary to program a
"good" RCW using CodeWarrior. The method here can be performed with any
JTAG adapter supported by OpenOCD, including the on-board CMSIS-DAP
(albeit very slowly).
These steps require LS1046A support in OpenOCD, which was added in [1].
[1] 5b70c1f679/
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
[trini: Add reference to doc/board/nxp/ls1046ardb.rst]
107 lines
3.9 KiB
ReStructuredText
107 lines
3.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
.. Copyright 2014 Broadcom Corporation.
|
|
|
|
Semihosting
|
|
===========
|
|
|
|
Semihosting is ARM's way of having a real or virtual target communicate
|
|
with a host or host debugger for basic operations such as file I/O,
|
|
console I/O, etc. Please see `Arm's semihosting documentation
|
|
<https://developer.arm.com/documentation/100863/latest/>`_ for more
|
|
information.
|
|
|
|
Platform Support
|
|
----------------
|
|
|
|
Versatile Express
|
|
^^^^^^^^^^^^^^^^^
|
|
|
|
For developing on armv8 virtual fastmodel platforms, semihosting is a
|
|
valuable tool since it allows access to image/configuration files before
|
|
eMMC or other NV media are available.
|
|
|
|
There are two main ARM virtual Fixed Virtual Platform (FVP) models,
|
|
`Versatile Express (VE) FVP and BASE FVP
|
|
<http://www.arm.com/products/tools/models/fast-models/foundation-model.php>`_.
|
|
The initial vexpress64 u-boot board created here runs on the VE virtual
|
|
platform using the license-free Foundation_v8 simulator. Fortunately,
|
|
the Foundation_v8 simulator also supports the BASE_FVP model which
|
|
companies can purchase licenses for and contain much more functionality.
|
|
So we can, in U-Boot, run either model by either using the VE FVP (default),
|
|
or turning on ``CONFIG_BASE_FVP`` for the more full featured model.
|
|
|
|
Rather than create a new armv8 board similar to ``armltd/vexpress64``, add
|
|
semihosting calls to the existing one, enabled with ``CONFIG_SEMIHOSTING``
|
|
and ``CONFIG_BASE_FVP`` both set. Also reuse the existing board config file
|
|
vexpress_aemv8.h but differentiate the two models by the presence or
|
|
absence of ``CONFIG_BASE_FVP``. This change is tested and works on both the
|
|
Foundation and Base fastmodel simulators.
|
|
|
|
QEMU
|
|
^^^^
|
|
|
|
Another ARM emulator which supports semihosting is `QEMU
|
|
<https://www.qemu.org/>`_. To enable semihosting, enable
|
|
``CONFIG_SERIAL_PROBE_ALL`` when configuring U-Boot, and use
|
|
``-semihosting`` when invoking QEMU. Adding ``-nographic`` can also be
|
|
helpful. When using a semihosted serial console, QEMU will block waiting
|
|
for input. This will cause the GUI to become unresponsive. To mitigate
|
|
this, try adding ``-nographic``. For more information about building and
|
|
running QEMU, refer to the :doc:`board documentation
|
|
<../board/emulation/qemu-arm>`.
|
|
|
|
OpenOCD
|
|
^^^^^^^
|
|
|
|
Any ARM platform can use semihosting with an attached debugger. One such
|
|
debugger with good support for a variety of boards and JTAG adapters is
|
|
`OpenOCD <https://openocd.org/>`_. Semihosting is not enabled by default,
|
|
so you will need to enable it::
|
|
|
|
$ openocd -f <your board config> -c init -c halt -c \
|
|
'arm semihosting enable' -c resume
|
|
|
|
Note that enabling semihosting can only be done after attaching to the
|
|
board with ``init``, and must be done while the CPU is halted. For a more
|
|
extended example, refer to the :ref:`LS1046ARDB docs <ls1046ardb_jtag>`.
|
|
|
|
Loading files
|
|
-------------
|
|
|
|
The semihosting code adds a "semihosting filesystem"::
|
|
|
|
load hostfs - <address> <image>
|
|
|
|
That will load an image from the host filesystem into RAM at the specified
|
|
address. If you are using U-Boot SPL, you can also use ``BOOT_DEVICE_SMH``
|
|
which will load ``CONFIG_SPL_FS_LOAD_PAYLOAD_NAME``.
|
|
|
|
Host console
|
|
------------
|
|
|
|
U-Boot can use the host's console instead of a physical serial device by
|
|
enabling ``CONFIG_SERIAL_SEMIHOSTING``. If you don't have
|
|
``CONFIG_DM_SERIAL`` enabled, make sure you disable any other serial
|
|
drivers.
|
|
|
|
Migrating from ``smhload``
|
|
--------------------------
|
|
|
|
If you were using the ``smhload`` command, you can migrate commands like::
|
|
|
|
smhload <file> <address> [<end var>]
|
|
|
|
to a generic load command like::
|
|
|
|
load hostfs - <address> <file>
|
|
|
|
The ``load`` command will set the ``filesize`` variable with the size of
|
|
the file. The ``fdt chosen`` command has been updated to take a size
|
|
instead of an end address. If you were adding the initramfs to your device
|
|
tree like::
|
|
|
|
fdt chosen <address> <end var>
|
|
|
|
you can now run::
|
|
|
|
fdt chosen <address> $filesize
|