The function got renamed to pwr_domain_pwr_down() but have a reference
to it for anyone wondering where it went.
Change-Id: Ica5fa11b9f18a7446c188e37b9f1d5508f4cf749
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
This patch introduces a platform-specific function to provide DLME
authentication features. While no platforms currently support DLME
authentication, this change offers a structured way for platforms
to define and expose their DLME authentication features, with the
flexibility to extend support in the future if needed.
Change-Id: Ia708914477c4d8cfee4809a9daade9a3e91ed073
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Introduces a platform-specific API to retrieve the ACPI table
region size. This will be used in a subsequent patch to specify
the minimum DLME size requirement for the DCE preamble.
Change-Id: I44ce9241733b22fea3cbce9d42f1c2cc5ef20852
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
RAS errors can cause problems for powerdown. On cpus like the A510,
receiving a RAS error after executing the powerdown `wfi` will deadlock
the core. The TRM suggests disabling the generation of interrupts.
However, which interrupts to disable is not apparent for generic code as
the meaning of each error record is *heavily* IMPDEF, despite the
standard format. Iterating over the list and disabling all is not
desirable as this might disable errors for components that do not have
an effect on the core that is powering down.
As such, leave this for the platform port to handle. Leave a note in the
porting guide so this is not missed.
Change-Id: I43c3f6f909fafc449d3b4e748b015b05338d9618
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Add documentation for the console framework on how to go about
instantiating a new console and how to use these consoles in TF-A.
This includes BOOT, RUNTIME and CRASH consoles.
Change-Id: I746d38f69f1b035d2e85d2589646e7fd67cb9cc3
Signed-off-by: Salman Nabi <salman.nabi@arm.com>
To allow for generic handling of a wakeup, this hook is no longer
expected to call wfi itself. Update the name everywhere to reflect this
expectation so that future platform implementers don't get misled.
Change-Id: Ic33f0b6da74592ad6778fd802c2f0b85223af614
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
The simplistic view of a core's powerdown sequence is that power is
atomically cut upon calling `wfi`. However, it turns out that it has
lots to do - it has to talk to the interconnect to exit coherency, clean
caches, check for RAS errors, etc. These take significant amounts of
time and are certainly not atomic. As such there is a significant window
of opportunity for external events to happen. Many of these steps are
not destructive to context, so theoretically, the core can just "give
up" half way (or roll certain actions back) and carry on running. The
point in this sequence after which roll back is not possible is called
the point of no return.
One of these actions is the checking for RAS errors. It is possible for
one to happen during this lengthy sequence, or at least remain
undiscovered until that point. If the core were to continue powerdown
when that happens, there would be no (easy) way to inform anyone about
it. Rejecting the powerdown and letting software handle the error is the
best way to implement this.
Arm cores since at least the a510 have included this exact feature. So
far it hasn't been deemed necessary to account for it in firmware due to
the low likelihood of this happening. However, events like GIC wakeup
requests are much more probable. Older cores will powerdown and
immediately power back up when this happens. Travis and Gelas include a
feature similar to the RAS case above, called powerdown abandon. The
idea is that this will improve the latency to service the interrupt by
saving on work which the core and software need to do.
So far firmware has relied on the `wfi` being the point of no return and
if it doesn't explicitly detect a pending interrupt quite early on, it
will embark onto a sequence that it expects to end with shutdown. To
accommodate for it not being a point of no return, we must undo all of
the system management we did, just like in the warm boot entrypoint.
To achieve that, the pwr_domain_pwr_down_wfi hook must not be terminal.
Most recent platforms do some platform management and finish on the
standard `wfi`, followed by a panic or an endless loop as this is
expected to not return. To make this generic, any platform that wishes
to support wakeups must instead let common code call
`psci_power_down_wfi()` right after. Besides wakeups, this lets common
code handle powerdown errata better as well.
Then, the CPU_OFF case is simple - PSCI does not allow it to return. So
the best that can be done is to attempt the `wfi` a few times (the
choice of 32 is arbitrary) in the hope that the wakeup is transient. If
it isn't, the only choice is to panic, as the system is likely to be in
a bad state, eg. interrupts weren't routed away. The same applies for
SYSTEM_OFF, SYSTEM_RESET, and SYSTEM_RESET2. There the panic won't
matter as the system is going offline one way or another. The RAS case
will be considered in a separate patch.
Now, the CPU_SUSPEND case is more involved. First, to powerdown it must
wipe its context as it is not written on warm boot. But it cannot be
overwritten in case of a wakeup. To avoid the catch 22, save a copy that
will only be used if powerdown fails. That is about 500 bytes on the
stack so it hopefully doesn't tip anyone over any limits. In future that
can be avoided by having a core manage its own context.
Second, when the core wakes up, it must undo anything it did to prepare
for poweroff, which for the cores we care about, is writing
CPUPWRCTLR_EL1.CORE_PWRDN_EN. The least intrusive for the cpu library
way of doing this is to simply call the power off hook again and have
the hook toggle the bit. If in the future there need to be more complex
sequences, their direction can be advised on the value of this bit.
Third, do the actual "resume". Most of the logic is already there for
the retention suspend, so that only needs a small touch up to apply to
the powerdown case as well. The missing bit is the powerdown specific
state management. Luckily, the warmboot entrypoint does exactly that
already too, so steal that and we're done.
All of this is hidden behind a FEAT_PABANDON flag since it has a large
memory and runtime cost that we don't want to burden non pabandon cores
with.
Finally, do some function renaming to better reflect their purpose and
make names a little bit more consistent.
Change-Id: I2405b59300c2e24ce02e266f91b7c51474c1145f
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
* changes:
feat(smccc): implement SMCCC_ARCH_FEATURE_AVAILABILITY
refactor(cm): clean up per-world context
refactor(cm): change owning security state when a feature is disabled
Move platform.mk inclusion in top level Makefile to permit a platform
specifying BRANCH_PROTECTION option.
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I1f662f82cd949eedfdbb61b9f66de15c46fb3106
SMCCC_ARCH_FEATURE_AVAILABILITY [1] is a call to query firmware about
the features it is aware of and enables. This is useful when a feature
is not enabled at EL3, eg due to an older FW image, but it is present in
hardware. In those cases, the EL1 ID registers do not reflect the usable
feature set and this call should provide the necessary information to
remedy that.
The call itself is very lightweight - effectively a sanitised read of
the relevant system register. Bits that are not relevant to feature
enablement are masked out and active low bits are converted to active
high.
The implementation is also very simple. All relevant, irrelevant, and
inverted bits combined into bitmasks at build time. Then at runtime the
masks are unconditionally applied to produce the right result. This
assumes that context managers will make sure that disabled features
do not have their bits set and the registers are context switched if
any fields in them make enablement ambiguous.
Features that are not yet supported in TF-A have not been added. On
debug builds, calling this function will fail an assert if any bits that
are not expected are set. In combination with CI this should allow for
this feature to to stay up to date as new architectural features are
added.
If a call for MPAM3_EL3 is made when MPAM is not enabled, the call
will return INVALID_PARAM, while if it is FEAT_STATE_CHECK, it will
return zero. This should be fairly consistent with feature detection.
The bitmask is meant to be interpreted as the logical AND of the
relevant ID registers. It would be permissible for this to return 1
while the ID returns 0. Despite this, this implementation takes steps
not to. In the general case, the two should match exactly.
Finally, it is not entirely clear whether this call replies to SMC32
requests. However, it will not, as the return values are all 64 bits.
[1]: https://developer.arm.com/documentation/den0028/galp1/?lang=en
Co-developed-by: Charlie Bareham <charlie.bareham@arm.com>
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I1a74e7d0b3459b1396961b8fa27f84e3f0ad6a6f
Add documentation for the feature where EL3 can be used to sign realm
attestation token requests using RMM_EL3_TOKEN_SIGN command.
This patch also adds documentation for the RMM_EL3_FEATURES features
command that can be used to discover support for features such as
RMM_EL3_TOKEN_SIGN.
Change-Id: Iab5a157761ed17931210c3702f813198fc9c4b3a
Signed-off-by: Raghu Krishnamurthy <raghupathyk@nvidia.com>
Until now, the attestation token size was limited by the size of the
shared buffer between RMM and TF-A. With this change, RMM can now
request the token in pieces, so they fit in the shared buffer. A new
output parameter was added to the SMC call, which will return (along
with the size of bytes copied into the buffer) the number of bytes
of the token that remain to be retrieved.
TF-A will keep an offset variable that will indicate the position in
the token where the next call will retrieve bytes from. This offset
will be increased on every call by adding the number number of bytes
copied. If the received hash size is not 0, TF-A will reset the
offset to 0 and copy from that position on.
The SMC call will now return at most the size of the shared buffer
in bytes on every call. Therefore, from now on, multiple SMC calls
may be needed to be issued if the token size exceeds the shared
buffer size.
Change-Id: I591f7013d06f64e98afaf9535dbea6f815799723
Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
In case of load error, platform may need to try another instance, either
from another storage, or from the same storage in case of PSA FWU. On
MTD devices such as NAND, it is required to define backup partitions.
A new function plat_setup_try_img_ops() should be called by platform
code to register handlers (plat_try_images_ops) to manage loading
other images.
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Lionel Debieve <lionel.debieve@foss.st.com>
Change-Id: Ideaecaf296c0037a26fb4e6680f33e507111378a
The plat_try_next_boot_source() API is not used by any upstream platform
and not used by platforms that asked for this API. It is then removed.
It will be replaced with a more generic interface in next patch.
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I298c7acace8c5efb3c66422d8d9280ecd08e5ade
* changes:
feat(stm32mp2): use early traces
feat(st-bsec): use early traces
refactor(st): replace STM32MP_EARLY_CONSOLE with EARLY_CONSOLE
feat(console): introduce EARLY_CONSOLE
feat(bl32): create an sp_min_setup function
* changes:
refactor(changelog): change all occurrences of RSS to RSE
refactor(qemu): change all occurrences of RSS to RSE
refactor(fvp): change all occurrences of RSS to RSE
refactor(fiptool): change all occurrences of RSS to RSE
refactor(psa): change all occurrences of RSS to RSE
refactor(fvp): remove leftovers from rss measured boot support
refactor(tc): change all occurrences of RSS to RSE
docs: change all occurrences of RSS to RSE
refactor(measured-boot): change all occurrences of RSS to RSE
refactor(rse): change all occurrences of RSS to RSE
refactor(psa): rename all 'rss' files to 'rse'
refactor(tc): rename all 'rss' files to 'rse'
docs: rename all 'rss' files to 'rse'
refactor(measured-boot): rename all 'rss' files to 'rse'
refactor(rss): rename all 'rss' files to 'rse'
Layout calculation is spread out between core BL1 logic and common
platform code. Relocate these into common platform code so they are
organised logically.
Change-Id: I8b05403e41b800957a0367316cecd373d10bb1a4
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
This is a generic porting of what was done on ST platforms with flag
STM32MP_EARLY_CONSOLE. It creates the flag and the prototype for
plat_setup_early_console(). This function depends on platform
implementation. This function call is added at the beginning of each BL
image early setup function.
The patch also introduce an extra log macro: EARLY_ERROR. This can
replace ERROR macro in code that will only be executed before the
default console is enabled, and will do nothing when the EARLY_CONSOLE
is not enabled. This can then save some space in memory.
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I77bf0a0c4289b4c7df94e4bfb783a938e05bf023
Changes all occurrences of "RSS" and "rss" in the documentation
to "RSE" and "rse".
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: Ia42078f5faa1db331b1e5a35f01faeaf1afacb5f
CryptoCell-712 and CryptoCell-713 drivers have been deprecated since
TF-A v2.9 and their removal was announced for TF-A v2.10 release.
See [1].
As the release is approaching, this patch deletes these drivers' code as
well as all references to them in the documentation and Arm platforms
code (Nuvoton platform is taken care in a subsequent patch). Associated
build options (ARM_CRYPTOCELL_INTEG and PLAT_CRYPTOCELL_BASE) have also
been removed and thus will have no effect if defined.
This is a breaking change for downstream platforms which use these
drivers.
[1] https://trustedfirmware-a.readthedocs.io/en/v2.9/about/release-information.html#removal-of-deprecated-drivers
Note that TF-A v3.0 release later got renumbered into v2.10.
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Change-Id: Idabbc9115f6732ac1a0e52b273d3380677a39813
This patch removes RAS_FFH_SUPPORT macro which is the combination of
ENABLE_FEAT_RAS and HANDLE_EA_EL3_FIRST_NS. Instead introduce an
internal macro FFH_SUPPORT which gets enabled when platforms wants
to enable lower EL EA handling at EL3. The internal macro FFH_SUPPORT
will be automatically enabled if HANDLE_EA_EL3_FIRST_NS is enabled.
FFH_SUPPORT along with ENABLE_FEAT_RAS will be used in source files
to provide equivalent check which was provided by RAS_FFH_SUPPORT
earlier. In generic code we needed a macro which could abstract both
HANDLE_EA_EL3_FIRST_NS and RAS_FFH_SUPPORT macros that had limitations.
Former was tied up with NS world only while the latter was tied to RAS
feature.
This is to allow Secure/Realm world to have their own FFH macros
in future.
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ie5692ccbf462f5dcc3f005a5beea5aa35124ac73
Current build infra defaults all cpufeats in defaults.mk and some
mandatory features are enabled in arch_features.mk and optional
arch features are enabled in platform specific makefile.
This fragmentation is sometime confusing to figure out which feature
is tied to which ARCH_MAJOR.ARCH_MINOR.
So, consolidating and grouping them for tracking and enabling makes
more sense. With this change we consolidate all ARCH feature handling
within arch_features.mk and disable all optional features that need
to be enabled to platform makefile.
This is an ongoing series of effort to consolidate and going forward
platform makefile should just specify ARCH_MAJOR and ARCH MINOR and
all mandatory feature should be selected based on arch_features.mk
any optional feature needed by the platform support can be enabled
by platform makefile.
It also makes it easier for platform ports to look upto arch_features.mk
and enable any optional feature that platform may need which are
supported from TF-A.
Change-Id: I18764008856d81414256b6cbabdfa42a16b8040d
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
Move documentation related to Arm(R) Ethos(TM)-N NPU driver from
docs/plat/arm/arm-build-options.rst to
docs/getting_started/build-options.rst.
Signed-off-by: Rajasekaran Kalidoss <rajasekaran.kalidoss@arm.com>
Change-Id: I388e8dcd3950b11bc3305f5e6396ee2e49c04493
A separate design document for Measured Boot covers the porting
guidelines for the Measured Boot interfaces. As a result,
the Measured Boot interfaces have been removed from the porting
guide and a link to the Measured Boot design document has been
provided.
Change-Id: Ia6bd2620d830aea6aececab4af7e10a6d737f025
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
PSCI specification reference in the documentation is updated
to point to latest specification and duplicate PSCI references are
removed.
Change-Id: I35ee365f08c557f3017af4d51f6d063a7501b27e
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
This patch adds a new optional member `pwr_domain_validate_suspend` to
the `plat_psci_ops_t` structure that allows a platform to optionally
perform platform specific validations in OS-initiated mode. This is
conditionally compiled into the build depending on the value of the
`PSCI_OS_INIT_MODE` build option.
In https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/17682,
the return type of the `pwr_domain_suspend` handler was updated from
`void` to `int` to allow a platform to optionally perform platform
specific validations in OS-initiated mode. However, when an error code
other than `PSCI_E_SUCCESS` is returned, the current exit path does not
undo the operations in `psci_suspend_to_pwrdown_start`, and as a result,
the system ends up in an unexpected state.
The fix in this patch prevents the need to undo the operations in
`psci_suspend_to_pwrdown_start`, by allowing the platform to first
perform any necessary platform specific validations before the PSCI
generic code proceeds to the point of no return where the CPU_SUSPEND
request is expected to complete successfully.
Change-Id: I05d92c7ea3f5364da09af630d44d78252185db20
Signed-off-by: Wing Li <wingers@google.com>
The current usage of RAS_EXTENSION in TF-A codebase is to cater for two
things in TF-A :
1. Pull in necessary framework and platform hooks for Firmware first
handling(FFH) of RAS errors.
2. Manage the FEAT_RAS extension when switching the worlds.
FFH means that all the EAs from NS are trapped in EL3 first and signaled
to NS world later after the first handling is done in firmware. There is
an alternate way of handling RAS errors viz Kernel First handling(KFH).
Tying FEAT_RAS to RAS_EXTENSION build flag was not correct as the
feature is needed for proper handling KFH in as well.
This patch breaks down the RAS_EXTENSION flag into a flag to denote the
CPU architecture `ENABLE_FEAT_RAS` which is used in context management
during world switch and another flag `RAS_FFH_SUPPORT` to pull in
required framework and platform hooks for FFH.
Proper support for KFH will be added in future patches.
BREAKING CHANGE: The previous RAS_EXTENSION is now deprecated. The
equivalent functionality can be achieved by the following
2 options:
- ENABLE_FEAT_RAS
- RAS_FFH_SUPPORT
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I1abb9ab6622b8f1b15712b12f17612804d48a6ec
This patch introduces support to handle traps from lower ELs for
IMPDEF system register accesses. The actual support is left to the
platforms to implement.
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Change-Id: I623d5c432b4ce4328b68f238c15b1c83df97c1e5
This patch introduces the 'pwr_domain_off_early' hook for
platforms wanting to perform housekeeping steps before the
PSCI framework starts the CPU power off sequence. Platforms
might also want to use ths opportunity to ensure that the
CPU off sequence can proceed.
The PSCI framework expects a return code of PSCI_E_DENIED,
if the platform wants to halt the CPU off sequence.
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Change-Id: I6980e84fc4d6cb80537a178d0d3d26fb28a13853
Following discussions in the reviews of the patch that introduced
plat_convert_pk() function [1], it was decided to deprecate it to
avoid weak function declaration.
A new optional function pointer convert_pk is added to crypto_lib_desc_t.
A new function crypto_mod_convert_pk() will either call
crypto_lib_desc.convert_pk() if it is defined, or do the same
as what was done by the weak function otherwise.
[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/17174
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Change-Id: I9358867f8bfd5e96b5ee238c066877da368e43c6
When porting TF-A to a new platform, it is essential to read the
threat model documents in conjunction with the porting guide to
understand the security responsibilities of each platform interface
to implement.
Add a note to highlight this in the porting guide.
Change-Id: Icd1e41ae4b15032b72531690dd82a9ef95ca0db5
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
The porting guide is currently hosted under the 'Getting started'
section. Yet, porting the full firmware to a new platform is probably
not the first thing that one would do. Before delving into the
details, one would probably start by building the code for an emulated
platform, such as Arm FVP.
Furthermore, the porting guide is such a big and important document
that it probably deserves being visible in the main table of contents.
Thus, move it just above the list of supported platforms.
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Change-Id: I51b3d2a93832505ab90d73c823f06f9540e84c77
This change creates the following directories under docs/
in order to provide a grouping for the content:
- components
- design
- getting_started
- perf
- process
In each of these directories an index.rst file is created
and this serves as an index / landing page for each of the
groups when the pages are compiled. Proper layout of the
top-level table of contents relies on this directory/index
structure.
Without this patch it is possible to build the documents
correctly with Sphinx but the output looks messy because
there is no overall hierarchy.
Change-Id: I3c9f4443ec98571a56a6edf775f2c8d74d7f429f
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
The implementation of the heap function plat_get_mbedtls_heap() becomes
mandatory for platforms supporting TRUSTED_BOARD_BOOT.
The shared Mbed TLS heap default weak function implementation is
converted to a helper function get_mbedtls_heap_helper() which can be
used by the platforms for their own function implementation.
Change-Id: Ic8f2994e25e3d9fcd371a21ac459fdcafe07433e
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Fix some typos and clarify some sentences.
Change-Id: Id276d1ced9a991b4eddc5c47ad9a825e6b29ef74
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
The previous commit added the infrastructure to load and save
ARMv8.3-PAuth registers during Non-secure <-> Secure world switches, but
didn't actually enable pointer authentication in the firmware.
This patch adds the functionality needed for platforms to provide
authentication keys for the firmware, and a new option (ENABLE_PAUTH) to
enable pointer authentication in the firmware itself. This option is
disabled by default, and it requires CTX_INCLUDE_PAUTH_REGS to be
enabled.
Change-Id: I35127ec271e1198d43209044de39fa712ef202a5
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Platforms are not allowed to use any file inside include/plat/arm or
plat/arm to prevent dependencies between Arm platforms and non-Arm
platforms.
Change-Id: I6dc336ab71134c8d2758761fac0e4716e2d7e6ff
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Using Sphinx linkcheck on the TF-A docs revealed some broken
or permanently-redirected links. These have been updated where
possible.
Change-Id: Ie1fead47972ede3331973759b50ee466264bd2ee
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
Fix links to SCC and FreeBSD. Direct links do not need any special
formatting.
Change-Id: I00f7343d029a30ec02dfaa0ef393b3197260cab9
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Replace all occurences of escaped underscore characters by plain ones.
This makes the text version of the porting guide easier to read and
grep into.
Change-Id: I7bf3b292b686be4c6d847a467b6708ac16544c90
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Also, update platform_def.h guidelines about includes in the porting
guide.
Change-Id: I1ae338c9dd3242b309f6d53687ba2cb755d488c3
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Commit ed51b51f7a ("Remove build option LOAD_IMAGE_V2") intended
to remove all code related to LOAD_IMAGE_V2=0 but missed a few things.
Change-Id: I16aaf52779dd4af1e134e682731328c5f1e5d622
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Corrects typos in core code, documentation files, drivers, Arm
platforms and services.
None of the corrections affect code; changes are limited to comments
and other documentation.
Change-Id: I5c1027b06ef149864f315ccc0ea473e2a16bfd1d
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
Crash reporting via the default consoles registered by MULTI_CONSOLE_API
has been broken since commit d35cc34 (Console: Use callee-saved
registers), which was introduced to allow console drivers written in C.
It's not really possible with the current crash reporting framework to
support console drivers in C, however we should make sure that the
existing assembly drivers that do support crash reporting continue to
work through the MULTI_CONSOLE_API.
This patch fixes the problem by creating custom console_putc() and
console_flush() implementations for the crash reporting case that do not
use the stack. Platforms that want to use this feature will have to link
plat/common/aarch64/crash_console_helpers.S explicitly.
Also update the documentation to better reflect the new reality (of this
being an option rather than the expected default for most platforms).
Change-Id: Id0c761e5e2fddaf25c277bc7b8ab603946ca73cb
Signed-off-by: Julius Werner <jwerner@chromium.org>