Since ARMv5, the clz instruction allows for efficient implementation of
ffs/fls with builtins. Until ARMv7 (with Thumb-2), this instruction is
only available in ARM mode. LTO makes it difficult to force specific
functions to be in ARM mode, as it is effectively a form of very
aggressive inlining. To work around this, fls/ffs are implemented in
assembly for ARMv5 and ARMv6 when compiling U-Boot in Thumb mode.
Overall, this saves around 75 bytes per call.
This code is synced with v5.15 of the Linux kernel.
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
This is required for architectures which do not support compressed kernel images (i.e. ARM64). This is only used while not booting via FIT image.
Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Introduce the new Kconfig symbol CONFIG_SPL_SYS_L2_PL310 to allow the
SPL to build cache-pl310.c.
Before this commit, the SPL could enable the PL310 L2 cache [1], but the
cache maintenance functions from cache-pl310.c were only useable for
non-SPL builds.
After enabling the cache one must be able to flush it, too. Thus this
commit allows cache-pl310.c to be included in the SPL build.
[1] See for example arch/arm/mach-imx/cache.c: v7_outer_cache_enable()
Signed-off-by: Philip Oberfichtner <pro@denx.de>
When u-boot is used as a chain-loaded bootloader (replacing OS kernel),
previous bootloader leaves data in RAM, that can be reused.
For example, on recent arm linux system, when chainloading u-boot,
there are initramfs and fdt in RAM prepared for OS booting. Initramfs
may be modified to store u-boot's payload, thus providing the ability to
use chainloaded u-boot to boot OS without any storage support.
Two config options added:
- SAVE_PREV_BL_INITRAMFS_START_ADDR
saves initramfs start address to 'prevbl_initrd_start_addr' environment
variable
- SAVE_PREV_BL_FDT_ADDR
saves fdt address to 'prevbl_fdt_addr' environment variable
Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Cc: Tom Rini <trini@konsulko.com>
This adds a boot method for loading the next stage from the host. It is
mostly modeled off of spl_load_image_ext. I am not really sure why/how
spl_load_image_fat uses three different methods to load the image, but
the simple case seems to work OK for now.
To control the presence of this boot method, we add a config symbol.
While we're at it, we update the original semihosting config symbol.
I think semihosting has some advantages of other forms of JTAG boot.
Common other ways to boot from JTAG include:
- Implementing DDR initialization through JTAG (typically with dozens of
lines of TCL) and then loading U-Boot. The DDR initialization
typically uses hard-coded register writes, and is not easily adapted
to different boards. BOOT_DEVICE_SMH allows booting with SPL,
leveraging U-Boot's existing DDR initialization code. This is the
method used by NXP's CodeWarrior IDE on Layerscape processors (see
AN12270).
- Loading a bootloader into SDRAM, waiting for it to initialize DDR, and
then loading U-Boot. This is tricky, because the debugger must stop the
boot after the bootloader has completed its work. Trying to load
U-Boot too early can cause failure to boot. This is the method used by
Xilinx with its Zynq(MP) processors.
- Loading SPL with BOOT_DEVICE_RAM and breaking before SPL loads the
image to load U-Boot at the appropriate place. This can be a bit
tricky, because the load address is dependent on the header size. An
elf with symbols must also be used in order to stop at the appropriate
point. BOOT_DEVICE_SMH can be viewed as an extension of this process,
where SPL automatically stops and tells the host where to place the
image.
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Ported from https://github.com/ARM-software/optimized-routines
These files are included from this repository, including the latest
git commit ID:
string/aarch64/memcpy.S: afd6244a1f8d
string/aarch64/memset.S: e823e3abf5f8
string/asmdefs.h: e823e3abf5f8
Note that memmove is also handled by the memcpy function.
Please note that when adding these optimized functions as default memset
memcpy functions in U-Boot, U-Boot fails to boot on the LX2160ARDB.
After the initial ATF output, no U-Boot output is shown on the serial
console. Some exception is triggered here in the very early boot process
as some of the assembler opcodes need the caches to be enabled.
Because of this, a follow-up patch will add a check to use a simple
non-optimized memset for the "cache disabled" case.
Note:
I also integrated and tested with the Linux versions of these optimized
functions. They are similar to the ones now integrated but these ARM
versions are still a small bit faster.
Signed-off-by: Stefan Roese <sr@denx.de>
Fix LTO build for some thumb-interwork usecases (such as for
da850evm_defconfig), where inline assmebly such as
mrc p15,0,r2,c1,c0,0
causes the compiler to fail during LTO linking with
Error: selected processor does not support `mrc p15,0,r2,c1,c0,0'
in Thumb mode
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>
We don't really want to have ARM-specific code in a generic file. Create
a new arch-specific function to hold it, and move it into that.
Make the function weak so that any arch can implement it.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
In case CONFIG_SYSRESET is set, do_reset from reset.c will not be available
anywere, even if SYSRESET is disabled for SPL/TPL.
'do_reset' is called from SPL for instance from the panic handler and
PANIC_HANG is not set
Signed-off-by: Claudius Heine <ch@denx.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Programs the following:
1. Redistributor PROCBASER configuration table (which
is common for all redistributors)
2. Redistributor pending table (PENDBASER), for all the
available redistributors.
Signed-off-by: Bharat Kumar Reddy Gooty <bharat.gooty@broadcom.com>
Signed-off-by: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>
Right now enabling SPL_FRAMEWORK will also enable it for the TPL in all
cases, making the TPL bigger. There may be cases where the TPL is really
size constrained due to its underlying ram size.
Therefore introduce a new TPL_FRAMEWORK option and make the relevant
conditionals check for both. The default is set to "y if SPL_FRAMEWORK"
to mimic the previous behaviour where the TPL would always get the
SPL framework if it was enabled in SPL.
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
ARMv7-M only supports the Thumb instruction set. Our current crt0 code does
not support it. With the patch we can build all unit tests of the EFI
subsystem that do not require crt0.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
Certain ARM architectures like ARMv7-A, ARMv7-R has support for
enabling caches using CP15 registers. To have a common support
for all these architectures, introduce a Kconfig symbol
SYS_ARM_CACHE_CP15 that selects cache-cp15.c
Tested-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from. So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry. Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.
In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.
This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents. There's also a few places where I found we did not have a tag
and have introduced one.
Signed-off-by: Tom Rini <trini@konsulko.com>
The tiny variants of memset and memcpy implementations can be
built for TPL as well, check whether a TPL build is in progress
and avoid including the default variants.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Follow bootz's pattern by moving the booti_setup to arch/arm/lib.
This allows to use booti_setup in other paths, e.g booting
an Android image containing Image format.
Note that kernel relocation is move out of booti_setup and it is the
caller's responsibility to do it and allows them do it differently. say,
cmd/booti.c just do a manually, while in the bootm path, we can use
bootm_load_os(with some changes).
Signed-off-by: Bin Chen <bin.chen@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
This pair of tests checks the StartImage boot service.
Each test loads an EFI application into memory and starts it.
One returns by calling the Exit boot service. The other returns directly.
The tests are not built on x86_64 because the relocation code for the efi
binary cannot be created.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
The previous setjmp-implementation (as a static inline function that
contained an 'asm volatile' sequence) was extremely fragile: (some
versions of) GCC optimised the set of registers. One critical example
was the removal of 'r9' from the clobber list, if -ffixed-reg9 was
supplied.
To increase robustness and ensure PCS-compliant behaviour, the setjmp
and longjmp implementation are now in assembly and closely match what
one would expect to find in a libc implementation.
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Andy Yan <andy.yan@rock-chips.com>
Rather than change asm files that come from Linux, add the symbols
to Kconfig. Since one of the symbols is for thumb2 builds, make
CPU_V7M always select them.
Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
The generic ARMv8 assembly code contains routines for setting up
a CCN interconnect, though the Freescale SoCs are the only user.
Link this code only for Freescale targets, this saves some precious
bytes in the chronically tight SPL.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Not every SoC needs to set up the GIC interrupt controller, so link
think code only when the respective config option is set.
This shaves off some bytes from the SPL code size.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Adding support for fdt fixup to update the
memory node in device tree for falcon boot.
This is needed for single stage or falcon
bootmode, to pass memory configuration to
kernel through DT memory node.
Signed-off-by: Ravi Babu <ravibabu@ti.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Today, we have cases where we wish to build all of U-Boot in Thumb2 mode for
various reasons. We also have cases where we only build SPL in Thumb2 mode due
to size constraints and wish to build the rest of the system in ARM mode. So
in this migration we introduce a new symbol as well, SPL_SYS_THUMB_BUILD to
control if we build everything or just SPL (or in theory, just U-Boot) in
Thumb2 mode.
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
We have long had available optimized versions of the memset and memcpy
functions that are borrowed from the Linux kernel. We should use these
in normal conditions as the speed wins in many workflows outweigh the
relatively minor size increase. However, we have a number of places
where we're simply too close to size limits in SPL and must be able to
make the size vs performance trade-off in those cases.
Cc: Philippe Reynes <tremyfr@yahoo.fr>
Cc: Eric Jarrige <eric.jarrige@armadeus.org>
Cc: Heiko Schocher <hs@denx.de>
Cc: Magnus Lilja <lilja.magnus@gmail.com>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Chander Kashyap <k.chander@samsung.com>
Cc: Akshay Saraswat <akshay.s@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Stefan Roese <sr@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
The predominantely 32-bit ARM targets try to compile the SPL in Thumb
mode to reduce code size.
The 64-bit AArch64 instruction set does not know an alternative, concise
encoding, so the Thumb build option should only be set for 32-bit
targets.
Likewise -marm machine options are only valid for ARMv7 targets.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Today we can compile a self-contained hello world efi test binary that
allows us to quickly verify whether the EFI loader framwork works.
We can use that binary outside of the self-contained test case though,
by providing it to a to-be-tested system via tftp.
This patch separates compilation of the helloworld.efi file from
including it in the u-boot binary for "bootefi hello". It also modifies
the efi_loader test case to enable travis to pick up the compiled file.
Because we're now no longer bloating the resulting u-boot binary, we
can enable compilation always, giving us good travis test coverage.
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
Add support for EFI apps on ARM. This includes start-up and relocation
code, plus a link script and some compiler setting changes.
Signed-off-by: Simon Glass <sjg@chromium.org>
[agraf: Remove whitespace change, add kconfig dep]
Signed-off-by: Alexander Graf <agraf@suse.de>
The bootz and booti commands rely on common functionality that is found
in common/bootm.c and common/bootm_os.c. They do not however rely on
the rest of cmd/bootm.c to be implemented so split them into their own
files. Have various Makefiles include the required infrastructure for
CONFIG_CMD_BOOT[IZ] as well as CONFIG_CMD_BOOTM. Move the declaration
of 'images' over to common/bootm.c.
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
As part of testing booting Linux kernels on Rockchip devices, it was
discovered by Ziyuan Xu and Sandy Patterson that we had multiple and for
some cases incomplete isb definitions. This was causing a failure to
boot of the Linux kernel.
In order to solve this problem as well as cover any corner cases that we
may also have had a number of changes are made in order to consolidate
things. First, <asm/barriers.h> now becomes the source of isb/dsb/dmb
definitions. This however introduces another complexity. Due to
needing to build SPL for 32bit tegra with -march=armv4 we need to borrow
the __LINUX_ARM_ARCH__ logic from the Linux Kernel in a more complete
form. Move this from arch/arm/lib/Makefile to arch/arm/Makefile and add
a comment about it. Now that we can always know what the target CPU is
capable off we can get always do the correct thing for the barrier. The
final part of this is that need to be consistent everywhere and call
isb()/dsb()/dmb() and NOT call ISB/DSB/DMB in some cases and the
function names in others.
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Acked-by: Sandy Patterson <apatterson@sightlogix.com>
Reported-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Reported-by: Sandy Patterson <apatterson@sightlogix.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Other payload than uImage is currently considered to be raw U-Boot
image. Check also for zImage in Falcon mode.
Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
Reviewed-by: Heiko Schocher <hs@denx.de>
Set the enable-method in the cpu node to PSCI, and create device
node for PSCI, when PSCI was enabled.
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
Import muldi3.S from Linux 4.4.6 , commit 0d1912303e54ed1b2a371be0bba51c384dd57326
on arm32. This file implements __aeabi_lmul and it's alias __muldi3, which
is needed when doing Thumb1 builds.
This patch also defines CONFIG_THUMB2_KERNEL and CONFIG_ARM_ASM_UNIFIED
which is necessary for correct build of these files both in ARM and
Thumb mode, just like Linux does.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Import __do_div64 from Linux 4.4.6 , commit 0d1912303e54ed1b2a371be0bba51c384dd57326
on arm32. This function is for some toolchains, which generate _udivmoddi4()
for 64 bit division.
Since we do not support stack unwinding, instead of importing the whole
asm/unwind.h and all the baggage, this patch defines empty UNWIND() macro.
This patch also defines CONFIG_THUMB2_KERNEL and CONFIG_ARM_ASM_UNIFIED
which is necessary for correct build of these files both in ARM and
Thumb mode, just like Linux does.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Sync the libgcc 32bit division and modulo operations with Linux 4.4.6 ,
commit 0d1912303e54ed1b2a371be0bba51c384dd57326 . The functions in these
four files are present in lib1funcs.S in Linux, so replace these files
with lib1funcs.S from Linux.
Since we do not support stack unwinding, instead of importing the whole
asm/unwind.h and all the baggage, this patch defines empty UNWIND() macro
in lib1funcs.S . Moreover, to make all of the functions available, define
CONFIG_AEABI , which is safe, because U-Boot is always compiled with ARM
EABI.
This patch also defines CONFIG_THUMB2_KERNEL and CONFIG_ARM_ASM_UNIFIED
which is necessary for correct build of these files both in ARM and
Thumb mode, just like Linux does.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Drop the underscore from the filenames of files implementing libgcc
routines. There is no functional change. This change is done to make
sync with Linux kernel easier.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Import unified.h from Linux kernel 4.4.6 , commit
0d1912303e54ed1b2a371be0bba51c384dd57326 . This header file contains
macros used in libgcc functions in Linux kernel on ARM and will be
needed for the libgcc sync.
Since unified.h defines the W(instr) macro, we must drop this from
the macro from memcpy.S , otherwise this triggers a warning about
symbol redefinition. In order to keep the changes to unified.h to
the minimum, tweak arch/arm/lib/Makefile such that it defines the
CONFIG_ARM_ASM_UNIFIED macro, which places .syntax unified into all
of the assembler files. This is mandatory.
Moreover, for Thumb2 build, define CONFIG_THUMB2_KERNEL macro if and
only if Thumb2 build is enabled. This macro is checked by unified.h
and toggles between ARM and Thumb2 variant of the instructions in the
assembler source files.
Finally, this patch defines __LINUX_ARM_ARCH__=N macro based on the
new CONFIG_SYS_ARM_ARCH Kconfig option. This macro selects between
more optimal and more dense codepaths which work on armv5 and newer
and less optimal codepaths which work on armv4 and possible armv3m.
Tegra2 needs the same special handling as it does in arch/arm/Makefile
to cater for the arm720t boot core.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
The current reset API implements a method to reset the entire system.
In the near future, I'd like to introduce code that implements the device
tree reset bindings; i.e. the equivalent of the Linux kernel's reset API.
This controls resets to individual HW blocks or external chips with reset
signals. It doesn't make sense to merge the two APIs into one since they
have different semantic purposes. Resolve the naming conflict by renaming
the existing reset API to sysreset instead, so the new reset API can be
called just reset.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
This is missing, with causes lldiv() to fail on boards with use the private
libgcc. Add the missing routine.
Code is available for using the CLZ instruction but it is not enabled at
present.
This comes from coreboot version 4.0.
Signed-off-by: Simon Glass <sjg@chromium.org>
When building a Thumb-1-only target with CONFIG_SYS_THUMB_BUILD,
some files fail to build, most of the time because they include
mcr instructions, which only exist for Thumb-2.
This patch introduces a Kconfig option CONFIG_THUMB2 and uses
it to select between Thumb-2 and ARM mode for the aforementioned
files.
Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
There can be only one do_reset(). When CONFIG_RESET is enabled this is
provided by the reset uclass, and ARM's version should be disabled.
Signed-off-by: Simon Glass <sjg@chromium.org>
This patch adds a minimal framework for Dickens CCN-504
interconnect configuration - mainly related to adding Clusters/cores
to snoop/DVM domain and setting QoS of the RN-I ports.
LS2085A platform makes use of these configurations to support
better network data performance and to boot a SMP Linux.
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>
On ARM v7M, the processor will return to ARM mode when executing
a blx instruction with bit 0 of the address == 0. Always set it
to 1 to stay in thumb mode.
Signed-off-by: Matt Porter <mporter@konsulko.com>
Introduce arch_reserve_stacks() to tailor gd->start_addr_sp and gd->irq_sp to
the architecture needs.
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
We have not had a good method to debug the early boot stage such as
lowlevel_init function. I guess developers generally use dedicated
debuggers for that, but it is difficult in some cases.
(For example, my debugger cannot connect to the ARM processor when
it is in the secure state. It sometimes happens when I need to
debug the early boot stage on ARM SoCs with secure extension.)
The low level debug feature in Linux would be also helpful for U-boot
when we are stucking in nasty problems where the console is not
available yet.
You have to enable CONFIG_DEBUG_LL to use this feature.
For now, only 8250-compatible UART devices are supported.
You can add a header file under arch/arm/include/debug/ directory
to support your UART device if necessary.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
The armv8 ARM Trusted Firmware (ATF) can be used to load various ATF
images and u-boot, and does this for virtual platforms by using
semihosting. This commit extends this idea by allowing u-boot to also
use semihosting to load the kernel/ramdisk/dtb. This eliminates the need
for a bootwrapper and produces a more realistic boot sequence with
virtual models.
Though the semihosting code is quite generic, support for armv7 in
fastmodel is less useful due to the wide range of available silicon
and the lack of a free armv7 fastmodel, so this change contains an
untested armv7 placeholder for the service trap opcode.
Please refer to doc/README.semihosting for a more detailed description
of semihosting and how it is used with the armv8 virtual platforms.
Signed-off-by: Darwin Rambo <drambo@broadcom.com>
Cc: trini@ti.com
Cc: fenghua@phytium.com.cn
Cc: bhupesh.sharma@freescale.com
