u-boot/doc/README.semihosting
Peter Hoyes b53bbca63b vexpress64: Add BASER_FVP vexpress board variant
The BASER_FVP board variant is implemented on top of the BASE_FVP board
config (which, in turn, is based on the Juno Versatile Express board
config). They all share a similar memory map - for BASER_FVP the map is
inverted from the BASE_FVP
(https://developer.arm.com/documentation/100964/1114/Base-Platform/Base---memory/BaseR-Platform-memory-map)

 * Create new TARGET_VEXPRESS64_BASER_FVP target, which uses the same
   board config as BASE_FVP and JUNO
 * Adapt vexpress_aemv8a.h header file to support BASER_FVP (and rename
   to vexpress_aemv8.h)
 * Enable config to switch to EL1 for the BASER_FVP
 * Create vexpress_aemv8r defconfig
 * Provide an MPU memory map for the BASER_FVP

For now, only single core boot is supported.

Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
[trini: Add MAINTAINERS, move BOOTCOMMAND to defconfig]
Signed-off-by: Tom Rini <trini@konsulko.com>
2021-09-02 10:17:45 -04:00

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SPDX-License-Identifier: GPL-2.0+
/*
* Copyright 2014 Broadcom Corporation.
*/
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
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471c/Bgbjjgij.html for more information.
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 (See
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.
The semihosting code adds a command:
smhload <image> <address> [env var]
That will load an image from the host filesystem into RAM at the specified
address and optionally store the load end address in the specified
environment variable.