We now have the CONFIG_SPL_DM for code within SPL to toggle caring about
DM or not. Without this change platforms that do enable CONFIG_DM but
not CONFIG_SPL_DM may be broken (such as OMAP5).
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Signed-off-by: Tom Rini <trini@konsulko.com>
Current many cpu use the same flush_cache() function, which just call
the flush_dcache_range().
So implement a weak flush_cache() for all the cpus to use.
In original weak flush_cache() in arch/arm/lib/cache.c, there has some
code for ARM1136 & ARM926ejs. But in the arch/arm/cpu/arm1136/cpu.c and
arch/arm/cpu/arm926ejs/cache.c, there implements a real flush_cache()
function as well. That means the original code for ARM1136 & ARM926ejs
in weak flush_cache() of arch/arm/lib/cache.c is totally useless.
So in this patch remove such code in flush_cache() and only call
flush_dcache_range().
Signed-off-by: Josh Wu <josh.wu@atmel.com>
Since some driver like ohci, lcd used dcache functions. But some ARM
cpu don't implement the invalidate_dcache_range()/flush_dcache_range()
functions.
To avoid compiling errors this patch adds an weak empty stub function
for all ARM cpu in arch/arm/lib/cache.c.
And ARM cpu still can implemnt its own cache functions on the cpu folder.
Signed-off-by: Josh Wu <josh.wu@atmel.com>
Reviewed-by: York Sun <yorksun@freescale.com>
This patch enables building SPL without
CONFIG_SPL_SERIAL_SUPPORT support.
Signed-off-by: Heiko Schocher <hs@denx.de>
[trini: Ensure we build arch/arm/imx-common on mx28]
Signed-off-by: Tom Rini <trini@konsulko.com>
The encoding of the sub instruction used to handle CONFIG_SYS_MALLOC_F_LEN
can only accept certain values, and the set of acceptable values differs
between the AArch32 and AArch64 instructions sets. The default value of
CONFIG_SYS_MALLOC_F_LEN works with either ISA. Tegra uses a non-default
value that can only be encoded in the AArch32 ISA. Fix the AArch64 crt0
assembly so it can handle completely arbitrary values.
Signed-off-by: Thierry Reding <treding@nvidia.com>
[twarren: trimmed Thierry's patch to remove changes already present]
Signed-off-by: Tom Warren <twarren@nvidia.com>
[swarren, cleaned up patch, wrote description, re-wrote subject]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
When CONFIG_SYS_THUMB_BUILD is defined these functions may be called from
Thumb code. Add the required ENTRY and ENDPROC bracketing so that BLX is
used to call these ARM functions, instead of plain BL, which will fail.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Pavel Machek <pavel@denx.de>
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>
With d6b72da0 we started including this file unconditionally. This
isn't allowed in a file that we also use on armv8. This will get
cleaned up a bit better once we really start using these same features
(and have similar fdt updates needed) on armv8.
Signed-off-by: Tom Rini <trini@konsulko.com>
In this case the secure code lives in RAM, and hence the memory node in
the device tree needs to be adjusted. This avoids that the OS will map
and possibly access the reservation.
Add support for setting CONFIG_ARMV7_SECURE_RESERVE_SIZE to carve out
such a region. We only support cutting off memory from the beginning or
the end of a RAM bank as we do not want to increase their number (which
would happen if punching a hole) for simplicity reasons
This will be used in a subsequent patch for Jetson-TK1.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
CONFIG_ARMV7_VIRT depends on CONFIG_ARMV7_NONSEC, thus doesn't need to
be taken into account additionally. CONFIG_ARMV7_PSCI is only set on
boards that support CONFIG_ARMV7_NONSEC, and it only works on those.
CC: Tang Yuantian <Yuantian.Tang@freescale.com>
CC: York Sun <yorksun@freescale.com>
CC: Steve Rae <srae@broadcom.com>
CC: Andre Przywara <andre.przywara@linaro.org>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Tested-by: Alison Wang <alison.wang@freescale.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
This adds NAND boot support for LS2085AQDS, using SPL framework.
Details of forming NAND image can be found in README.
Signed-off-by: Scott Wood <scottwood@freescale.com>
[York Sun: Remove +S from defconfig after commit 252ed872]
Signed-off-by: York Sun <yorksun@freescale.com>
This value is not used by the network stack and is available in the
global data, so stop passing it around. For the one legacy function
that still expects it (init op on old Ethernet drivers) pass in the
global pointer version directly to avoid changing that interface.
Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reported-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
(Trival fix to remove an unneeded variable declaration in 4xx_enet.c)
In the case where the arch defines a custom map_sysmem(), make sure that
including just mapmem.h is sufficient to have these functions as they
are when the arch does not override it.
Also split the non-arch specific functions out of common.h
Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
The TTBR0 register and Table Descriptors of the ARMv7 TLB weren't being
properly set to allow for the configuration specified caching modes to
be active over DRAM. This commit fixes those issues.
Signed-off-by: Bryan Brinsko <bryan.brinsko@rockwellcollins.com>
Now that loading files using semihosting can be done using
a command in standard scripts, and we have rewritten the boardfile
and added it to the Vexpress64, let's delete the external
interface to the semihosting file retrieveal and rely solely
on these commands, and staticize them inside that file so the
whole business is self-contained.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Instead of sprinkling custom code and calls over the Vexpress64
boardfile, create a command that loads images using semihosting
just like we would load from flash memory of over the network,
using a special command:
smhload <image> <address>
This will make it possible to remove some custom calls and
code and make the boot easier.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
The semihosting trap call does not like being inlined, probably
because that will mean register reordering screwing up the return
value in r0, so tag this function "noinline".
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Allocate memory space for pre-allocation malloc and zero global data.
This code is partly from crt0.S.
Signed-off-by: David Feng <fenghua@phytium.com.cn>
The way the PSCI DT update happens currently means we pull in
<asm/armv7.h> everywhere, including on ARMv8 and that in turn brings in
<asm/io.h> for some non-PSCI related things that header needs to deal
with.
To fix this, we rework the hook slightly. A good portion of
arch/arm/cpu/armv7/virt-dt.c is common looking and I hope that when PSCI
is needed on ARMv8 we can re-use this by and large. So rename the
current hook to psci_update_dt(), move the prototype to <asm/psci.h> and
add an #ifdef that will make re-use later easier.
Reported-by: York Sun <yorksun@freescale.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: York Sun <yorksun@freescale.com>
Cc: Ian Campbell <ijc@hellion.org.uk>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: York Sun <yorksun@freescale.com>
For ARM architecture, enable the CONFIG_USE_ARCH_MEMSET/MEMCPY,
will highly increase the memset/memcpy performance. This is able
thanks to the ARM multiple register instructions.
Unfortunatelly the relocation is done without the cache enabled,
so it takes some time, but zeroing the BSS memory takes much more
longer, especially for the configs with big static buffers.
A quick test confirms, that the boot time improvement after using
the arch memcpy for relocation has no significant meaning.
The same test confirms that enable the memset for zeroing BSS,
reduces the boot time.
So this patch enables the arch memset for zeroing the BSS after
the relocation process. For ARM boards, this can be enabled
in board configs by defining: 'CONFIG_USE_ARCH_MEMSET'.
This was tested on Trats2.
A quick test with trace. Boot time from start to main_loop() entry:
- ~1384ms - before this change
- ~888ms - after this change
Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@konsulko.com>
At present SPL uses a single stack, either CONFIG_SPL_STACK or
CONFIG_SYS_INIT_SP_ADDR. Since some SPL features (such as MMC and
environment) require a lot of stack, some boards set CONFIG_SPL_STACK to
point into SDRAM. They then set up SDRAM very early, before board_init_f(),
so that the larger stack can be used.
This is an abuse of lowlevel_init(). That function should only be used for
essential start-up code which cannot be delayed. An example of a valid use is
when only part of the SPL code is visible/executable, and the SoC must be set
up so that board_init_f() can be reached. It should not be used for SDRAM
init, console init, etc.
Add a CONFIG_SPL_STACK_R option, which allows the stack to be moved to a new
address before board_init_r() is called in SPL.
The expected SPL flow (for CONFIG_SPL_FRAMEWORK) is documented in the README.
Signed-off-by: Simon Glass <sjg@chromium.org>
For version 1:
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Heiko Schocher <hs@denx.de>
Tested-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
This is already set up in crt0.S. We don't need a new structure and don't
really want one in the 'data' section of the image, since it will be empty
and crt0.S's changes will be ignored.
As an interim measure, remove it only if CONFIG_DM is not defined. This
allows us to press ahead with driver model in SPL and allow the stragglers
to catch up.
Signed-off-by: Simon Glass <sjg@chromium.org>
This is still a non-generic board.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Matthias Weisser <weisserm@arcor.de>
Acked-by: Marek Vasut <marex@denx.de>
Flushing L3 cache in CCN-504 requries d-cache to be disabled. Using
assembly function to guarantee stack is not used before flushing is
completed. Timeout is needed for simualtor on which CCN-504 is not
implemented. Return value can be checked for timeout situation.
Change bootm.c to disable dcache instead of simply flushing, required
by flushing L3.
Signed-off-by: York Sun <yorksun@freescale.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>
If we don't know the relocation address, the raw values are not very useful.
Show the pre-relocation values as well as these can be looked up in
System.map, etc.
Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
in thumb mode compiler says for example for arch/arm/lib/cache-cp15.c
when enabling CONFIG_SYS_THUMB_BUILD:
{standard input}: Assembler messages:
{standard input}:373: Error: selected processor does not support Thumb mode `mrc p15,0,r4,c1,c0,0'
{standard input}:416: Error: selected processor does not support Thumb mode `mcr p15,0,r3,c2,c0,0'
so, if caches are disabled, do not use this command on arm926ejs.
used on at91 in SPL, to reduce size of SPL.
Signed-off-by: Heiko Schocher <hs@denx.de>
We need to get rid of this SPL-specific setting of the global_data pointer.
It is already set up in start.S immediately before board_init_f() is called,
and there may be information there that is needed (e.g. pre-reloc malloc
info).
Signed-off-by: Simon Glass <sjg@chromium.org>
Resynchronize memcpy/memset with kernel 3.17 and build them in
Thumb2 mode (unified syntax). Those assembler files can be built
and linked in ARM mode too, however when calling them from Thumb2
built code, the stack got corrupted and the copy did not succeed
(the exact details have not been traced back). However, the Linux
kernel builds those files in Thumb2 mode. Hence U-Boot should
build them in Thumb2 mode too when CONFIG_SYS_THUMB_BUILD is set.
To build the files without warning, some assembler instructions
had to be replaced with their UAL compliant variant (thanks
Jeroen for this input).
To build the file in Thumb2 mode the implicit-it=always option need
to be set to generate Thumb2 compliant IT instructions where needed.
We add this option to the general AFLAGS when building for Thumb2.
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Commit 8bc347e2ec "ARM: bootm: Allow booting in secure mode on hyp capable
systems" added the capability to select nonsec vs sec mode boot via an
environment var.
There is a subtle gotcha with this functionality, which is that the PSCI nodes
are still created in the fdt (via armv7_update_dt->fdt_psci) even when booting
in secure mode. Which means that if the kernel is PSCI aware then it will fail
to boot because it will try and do PSCI from secure world, which won't work.
This likely didn't get noticed before because the original purpose was to
support booting the legacy linux-sunxi kernels which don't understand PSCI.
To fix expose boot_nonsec (renaming with armv7_ prefix) outside of bootm.c and
use from the virt-dt code.
As well as avoiding the creation of the PSCI nodes we should also avoid
reserving the secure RAM, so do so.
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
By rearranging the functions in the semihosting code we can
avoid forward-declaration of the internal static functions.
This puts the stuff in a logical order: read/open/close/len
and then higher-order functions follow at the end.
Cc: Darwin Rambo <drambo@broadcom.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Mark Hambleton <mark.hambleton@arm.com>
Cc: Tom Rini <trini@ti.com>
Acked-by: Steve Rae <srae@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
There is currently a regression when using newer ARM64 compilers
for semihosting: the way long types are inferred from context
is no longer the same.
The semihosting runtime uses long and size_t, so use this
explicitly in the semihosting code and interface, and voila:
the code now works again.
Tested with aarch64-linux-gnu-gcc: Linaro GCC 4.9-2014.09.
Cc: Darwin Rambo <drambo@broadcom.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Mark Hambleton <mark.hambleton@arm.com>
Cc: Tom Rini <trini@ti.com>
Acked-by: Steve Rae <srae@broadcom.com>
Suggested-by: Mark Hambleton <mark.hambleton@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
The semihosting code exposes internal file handle handling
functions to read(), open(), close() and get the length of
a certain file handle.
However the code using it is only interested in either
reading and entire named file into memory or getting the
file length of a file referred by name. No file handles
are used.
Thus make the file handle code internal to this file by
removing these functions from the semihosting header file
and staticize them.
This gives us some freedom to rearrange the semihosting
code without affecting the external interface.
Cc: Darwin Rambo <drambo@broadcom.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Mark Hambleton <mark.hambleton@arm.com>
Cc: Tom Rini <trini@ti.com>
Acked-by: Steve Rae <srae@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Implement an API that can be used by drivers to allocate memory from a
pool that is mapped uncached. This is useful if drivers would otherwise
need to do extensive cache maintenance (or explicitly maintaining the
cache isn't safe).
The API is protected using the new CONFIG_SYS_NONCACHED_MEMORY setting.
Boards can set this to the size to be used for the non-cached area. The
area will typically be right below the malloc() area, but architectures
should take care of aligning the beginning and end of the area to honor
any mapping restrictions. Architectures must also ensure that mappings
established for this area do not overlap with the malloc() area (which
should remain cached for improved performance).
While the API is currently only implemented for ARM v7, it should be
generic enough to allow other architectures to implement it as well.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Implement an API that can be used by drivers to allocate memory from a
pool that is mapped uncached. This is useful if drivers would otherwise
need to do extensive cache maintenance (or explicitly maintaining the
cache isn't safe).
The API is protected using the new CONFIG_SYS_NONCACHED_MEMORY setting.
Boards can set this to the size to be used for the non-cached area. The
area will typically be right below the malloc() area, but architectures
should take care of aligning the beginning and end of the area to honor
any mapping restrictions. Architectures must also ensure that mappings
established for this area do not overlap with the malloc() area (which
should remain cached for improved performance).
While the API is currently only implemented for ARM v7, it should be
generic enough to allow other architectures to implement it as well.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Older Linux kernels will not properly boot in hyp mode, add support for a
bootm_boot_mode environment variable, which can be set to "sec" or "nonsec"
to force booting in secure or non-secure mode when build with non-sec support.
The default behavior can be selected through CONFIG_ARMV7_BOOT_SEC_DEFAULT,
when this is set booting in secure mode is the default. The default setting
for this Kconfig option is N, preserving the current behavior of booting in
non-secure mode by default when non-secure mode is supported.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
For SPL it is sometimes useful to have a simple malloc() just to permit
driver model to work, in the cases where the full malloc() is not made
available by the board config.
Signed-off-by: Simon Glass <sjg@chromium.org>
CONFIG_CPU_ARM1136 was introduced into Kconfig by commit 2e07c249a6
(kconfig: arm: introduce symbol for ARM CPUs).
This commit removes all the defines of CONFIG_ARM1136 and replaces
the only reference in arch/arm/lib/cache.c with CONFIG_CPU_ARM1136.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
CONFIG_CPU_ARM926EJS was introduced into Kconfig by commit 2e07c249a6
(kconfig: arm: introduce symbol for ARM CPUs).
This commit removes all the defines of CONFIG_ARM926EJS and replaces
the only reference in arch/arm/lib/cache.c with CONFIG_CPU_ARM926EJS.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Commit 3ff46cc4 fixed exception vectors setting in
the general ARM case, by either copying the exception
and indirect vector tables to normal (0x00000000) or
high (0xFFFF0000) vectors address, or setting VBAR to
U-Boot's base if applicable.
i.MX27 SoC is ARM926E-JS, thus has only normal and
high options, but does not provide RAM at 0xFFFF0000
and has only ROM at 0x00000000; it is therefore not
possible to move or change its exception vectors.
Besides, i.MX27 ROM code does provide an indirect
vectors table but at a non-standard address and with
the reset and reserved vectors missing.
Turn the current vector relocation code into a weak
routine called after relocate_code from crt0, and add
strong version for i.MX27.
Series-Cc: Heiko Schocher <hs@denx.de>
Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Tested-by: Stefano Babic <sbabic@denx.de>
Tested-by: Philippe Reynes <tremyfr@gmail.com>
Tested-by: Philippe Reynes <tremyfr@yahoo.fr>
size_t is the canonical type to represent variables that contain a size.
Use it instead of signed integer. Physical addresses can be larger than
32-bit, so use a more appropriate type for them as well. phys_addr_t is
a type that is 32-bit on systems that use 32-bit addresses and 64-bit if
the system is 64-bit or uses a form of physical address extension to use
a larger address space on 32-bit systems. Using these types the same API
can be implemented on a wider range of systems.
Signed-off-by: Thierry Reding <treding@nvidia.com>
This is a MIME GnuPG-signed message. If you see this text, it means that
your E-mail or Usenet software does not support MIME signed messages.
The Internet standard for MIME PGP messages, RFC 2015, was published in 1996.
To open this message correctly you will need to install E-mail or Usenet
software that supports modern Internet standards.
This reverts commit 1e96220a56.
Remove duplicated vxworks.h header.
The same change was done by
"ARM: prevent compiler warnings from bootm.c"
(sha1: 8d196e52b5)
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Before this commit, the stack addresses for IRQ and FIQ modes,
IRQ_STACK_START and FIQ_STACK_START, were computed in interrupt_init but
they were not used.
This commit sets the stack pointers for IRQ and FIQ modes.
Signed-off-by: Georges Savoundararadj <savoundg@gmail.com>
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
This commit relocates the exception vectors.
As ARM1176 and ARMv7 have the security extensions, it uses VBAR. For
the other ARM processors, it copies the relocated exception vectors to
the correct address: 0x00000000 or 0xFFFF0000.
Signed-off-by: Georges Savoundararadj <savoundg@gmail.com>
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Tom Warren <twarren@nvidia.com>
A regression was introduced in commit 41623c91. The consequence of that
is the non-relocation of the section .vectors symbols :
_undefined_instruction, _software_interrupt, _prefetch_abort,
_data_abort, _not_used, _irq and _fiq.
Before commit 41623c91, the exception vectors were in a .text section.
The .text section has the attributes allocatable and executable [1].
In commit 41623c91, a specific section is created, called .vectors, with
the attribute executable only.
What have changed between commit 41623c91^ and 41623c91 is the attribute
of the section which contains the exception vectors.
An allocatable section is "a section [that] occupies memory during
process execution" [1] which is the case of the section .vectors.
Adding the lacking attribute (SHF_ALLOC or "a") for the definition of
the section .vectors fixed the issue.
To summarize, the fix has to mark .vectors as allocatable because the
exception vectors reside in "memory during execution" and they need to
be relocated.
[1] http://man7.org/linux/man-pages/man5/elf.5.html
Signed-off-by: Georges Savoundararadj <savoundg@gmail.com>
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Because CONFIG_MMU is never defined in U-Boot,
the non-MMU code in debug.S is always used.
Unfortunately, the number of arguments of the addruart macro
in Linux is different between MMU and non-MMU.
This causes a build error when importing some debug macros
using the third argument. (For ex. arch/arm/include/debug/exynos.S)
Pass the third argument to the non-MMU addruart to avoid such a problem.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Tested-by: Przemyslaw Marczak <p.marczak@samsung.com>
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>