GitLab

It doesn't make sense to use the `-pedantic` flag when building the
Trusted Firmware as we use GNU extensions and so our code is not
fully ISO C compliant. This flag only makes sense if the code intends to
be ISO C compliant.

Change-Id: I6273564112759ff57f03b273f5349733a5f38aef
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Add the description on hikey and how to build.
Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>

Change-Id: I92fd2fb920fcfc31bfcdadae787d8c84c5ca463b
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

This options enables an implementation of SHA-256 that has a smaller
code footprint (~1.6 KB less) but is also ~30% slower. For ARM
platforms, code size is currently considered more important than
execution speed in the mbed TLS crypto module.

Added a small note about this option to the documentation of the
authentication framework.

Change-Id: I4c0b221ea5d3466465261316ba07b627fa01b233
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Platforms aligned with TBBR are supposed to use their own OIDs, but
defining the same macros with different OIDs does not provide any
value (at least technically).

For easier use of TBBR, this commit allows platforms to reuse the OIDs
obtained by ARM Ltd.  This will be useful for non-ARM vendors that
do not need their own extension fields in their certificate files.

The OIDs of ARM Ltd. have been moved to include/tools_share/tbbr_oid.h

Platforms can include <tbbr_oid.h> instead of <platform_oid.h> by
defining USE_TBBR_DEFS as 1.  USE_TBBR_DEFS is 0 by default to keep the
backward compatibility.

For clarification, I inserted a blank line between headers from the
include/ directory (#include <...>) and ones from a local directory
(#include "..." ).
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This Linaro release updates just the binaries:

Linaro binaries upgraded 16.12 --> 17.01

The toolchain remains at 5.3-2015.05 (gcc 5.3) for both AArch64
and AArch32.

The ARM TF codebase has been tested against these new binaries. This patch
updates the User Guide to reflect that the 17.01 release is now a supported
Linaro Release.

Change-Id: I83c579dabd3fa9861ba0d41507036efbd87abcb5
Signed-off-by: David Cunado <david.cunado@arm.com>

The behaviour of assert() now depends on the value of the new optional
platform define `PLAT_LOG_LEVEL_ASSERT`. This defaults to `LOG_LEVEL` if
not defined by the platform.

- If `PLAT_LOG_LEVEL_ASSERT` >= `LOG_LEVEL_VERBOSE`, it prints the file
  name, line and asserted expression.
- If `PLAT_LOG_LEVEL_ASSERT` >= `LOG_LEVEL_INFO`, it prints the file
  name and line.
- If not, it doesn't print anything.

Note the old behaviour was to print the function name whereas now it
prints the file name. This reduces memory usage because the file name is
shared between all assert calls in a given file. Also, the default
behaviour in debug builds is to no longer print the asserted expression,
greatly reducing the string usage.

For FVP debug builds this change saves approximately:

              No TBBR    TBBR
        BL1    1.6 KB   2.2 KB
        BL2    1.7 KB   2.1 KB
        BL31   2.6 KB   3.3 KB

Change-Id: I2947569d593df0b25611dc3c7a6096f42155c115
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

AEMv8-A Model release v8.4 has been made available and Trusted Firmware
has been tested against these versions as part of its CI system. This
patch updates the user guide documentation to reflect the version of AEM
and Cortex Models that Trusted Firmware has been tested against.

Additionally, ARM FVPs FVP_Base_Cortex-A57x1-A53x1 and
FVP_Base_Cortex-A57x2-A53x4 are removed from the list of tested FVPs
as they are currently not being tested with the latest version of ARM
Trusted Firmware.

Also, documentation and links to Linaro pages have been updated to
reflect the changes in the ARM community document hosting.

Change-Id: Idae97303ce0929c82b137017de84ce94678f6f2b
Signed-off-by: David Cunado <david.cunado@arm.com>

In AArch64, privileged exception levels control the execution state
(a.k.a. register width) of the immediate lower Exception Level; i.e.
whether the lower exception level executes in AArch64 or AArch32 state.
For an exception level to have its execution state changed at run time,
it must request the change by raising a synchronous exception to the
higher exception level.

This patch implements and adds such a provision to the ARM SiP service,
by which an immediate lower exception level can request to switch its
execution state. The execution state is switched if the request is:

  - raised from non-secure world;

  - raised on the primary CPU, before any secondaries are brought online
    with CPU_ON PSCI call;

  - raised from an exception level immediately below EL3: EL2, if
    implemented; otherwise NS EL1.

If successful, the SMC doesn't return to the caller, but to the entry
point supplied with the call. Otherwise, the caller will observe the SMC
returning with STATE_SW_E_DENIED code. If ARM Trusted Firmware is built
for AArch32, the feature is not supported, and the call will always
fail.

For the ARM SiP service:

  - Add SMC function IDs for both AArch32 and AArch64;
  - Increment the SiP service minor version to 2;
  - Adjust the number of supported SiP service calls.

Add documentation for ARM SiP service.

Fixes ARM-software/tf-issues#436

Change-Id: I4347f2d6232e69fbfbe333b340fcd0caed0a4cea
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Since Issue B (November 2016) of the SMC Calling Convention document
standard SMC calls are renamed to yielding SMC calls to help avoid
confusion with the standard service SMC range, which remains unchanged.

http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf



This patch adds a new define for yielding SMC call type and deprecates
the current standard SMC call type. The tsp is migrated to use this new
terminology and, additionally, the documentation and code comments are
updated to use this new terminology.

Change-Id: I0d7cc0224667ee6c050af976745f18c55906a793
Signed-off-by: David Cunado <david.cunado@arm.com>

The build option `ENABLE_ASSERTIONS` should be used instead. That way
both C and ASM assertions can be enabled or disabled together.

All occurrences of `ASM_ASSERTION` in common code and ARM platforms have
been replaced by `ENABLE_ASSERTIONS`.

ASM_ASSERTION has been removed from the user guide.

Change-Id: I51f1991f11b9b7ff83e787c9a3270c274748ec6f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Add the new build option `ENABLE_ASSERTIONS` that controls whether or
not assert functions are compiled out. It defaults to 1 for debug builds
and to 0 for release builds.

Additionally, a following patch will be done to allow this build option
to hide auxiliary code used for the checks done in an `assert()`. This
code is is currently under the DEBUG build flag.

Assert messages are now only printed if LOG_LEVEL >= LOG_LEVEL_INFO,
which is the default for debug builds.

This patch also updates the User Guide.

Change-Id: I1401530b56bab25561bb0f274529f1d12c5263bc
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch introduces a build option to enable D-cache early on the CPU
after warm boot. This is applicable for platforms which do not require
interconnect programming to enable cache coherency (eg: single cluster
platforms). If this option is enabled, then warm boot path enables
D-caches immediately after enabling MMU.

Fixes ARM-Software/tf-issues#456

Change-Id: I44c8787d116d7217837ced3bcf0b1d3441c8d80e
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

ARM platforms have migrated to the translation tables library v2.
However, for testing purposes, it can be useful to temporarily switch
back to the old version.

This patch introduces the option `ARM_XLAT_TABLES_LIB_V1`, that switches
to v1 of the library when is set to 1. By default, it is 0, so that ARM
platforms use the new version unless specifically stated.

Updated User Guide.

Change-Id: I53d3c8dd97706f6af9c6fca0364a88ef341efd31
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Introduce new build option ENABLE_STACK_PROTECTOR. It enables
compilation of all BL images with one of the GCC -fstack-protector-*
options.

A new platform function plat_get_stack_protector_canary() is introduced.
It returns a value that is used to initialize the canary for stack
corruption detection. Returning a random value will prevent an attacker
from predicting the value and greatly increase the effectiveness of the
protection.

A message is printed at the ERROR level when a stack corruption is
detected.

To be effective, the global data must be stored at an address
lower than the base of the stacks. Failure to do so would allow an
attacker to overwrite the canary as part of an attack which would void
the protection.

FVP implementation of plat_get_stack_protector_canary is weak as
there is no real source of entropy on the FVP. It therefore relies on a
timer's value, which could be predictable.

Change-Id: Icaaee96392733b721fa7c86a81d03660d3c1bc06
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

This API makes sure that all the characters sent to the crash console
are output before returning from it.

Porting guide updated.

Change-Id: I1785f970a40f6aacfbe592b6a911b1f249bb2735
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch updates the User Guide to recommend the latest version
of mbed TLS library to use with ARM Trusted Firmware.

 - Upgrade mbed TLS library:   2.2.1 -> 2.4.2

Change-Id: Ifb5386fec0673d6dbfdaa474233e397afc279c85

This patch modifies some of the functions in ARM platform layer to cater
for the case when multi-threading `MT` is set in MPIDR. A new build flag
`ARM_PLAT_MT` is added, and when enabled, the functions accessing MPIDR
now assume that the `MT` bit is set for the platform and access the bit
fields accordingly.

Also, a new API plat_arm_get_cpu_pe_count is added when `ARM_PLAT_MT` is
enabled, returning the PE count within the physical cpu corresponding to
`mpidr`.

Change-Id: I04ccf212ac3054a60882761f4087bae299af13cb
Signed-off-by: Summer Qin <summer.qin@arm.com>

Fixes ARM-software/tf-issues#463

Change-Id: I73e0c5fbd87004953df8b1fa19319ad562ecc867
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

ARM erratum 855873 applies to all Cortex-A53 CPUs.
The recommended workaround is to promote "data cache clean"
instructions to "data cache clean and invalidate" instructions.
For core revisions of r0p3 and later this can be done by setting a bit
in the CPUACTLR_EL1 register, so that hardware takes care of the promotion.
As CPUACTLR_EL1 is both IMPLEMENTATION DEFINED and can be trapped to EL3,
we set the bit in firmware.
Also we dump this register upon crashing to provide more debug
information.

Enable the workaround for the Juno boards.

Change-Id: I3840114291958a406574ab6c49b01a9d9847fec8
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

TLBI instructions for EL3 won't have the desired effect under specific
circumstances in Cortex-A57 r0p0. The workaround is to execute DSB and
TLBI twice each time.

Even though this errata is only needed in r0p0, the current errata
framework is not prepared to apply run-time workarounds. The current one
is always applied if compiled in, regardless of the CPU or its revision.

This errata has been enabled for Juno.

The `DSB` instruction used when initializing the translation tables has
been changed to `DSB ISH` as an optimization and to be consistent with
the barriers used for the workaround.

Change-Id: Ifc1d70b79cb5e0d87e90d88d376a59385667d338
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Added APIs to add and remove regions to the translation tables
dynamically while the MMU is enabled. Only static regions are allowed
to overlap other static ones (for backwards compatibility).

A new private attribute (MT_DYNAMIC / MT_STATIC) has been added to
flag each region as such.

The dynamic mapping functionality can be enabled or disabled when
compiling by setting the build option PLAT_XLAT_TABLES_DYNAMIC to 1
or 0. This can be done per-image.

TLB maintenance code during dynamic table mapping and unmapping has
also been added.

Fixes ARM-software/tf-issues#310

Change-Id: I19e8992005c4292297a382824394490c5387aa3b
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

The current PSCI implementation can apply certain optimizations upon the
assumption that all PSCI participants are cache-coherent.

  - Skip performing cache maintenance during power-up.

  - Skip performing cache maintenance during power-down:

    At present, on the power-down path, CPU driver disables caches and
    MMU, and performs cache maintenance in preparation for powering down
    the CPU. This means that PSCI must perform additional cache
    maintenance on the extant stack for correct functioning.

    If all participating CPUs are cache-coherent, CPU driver would
    neither disable MMU nor perform cache maintenance. The CPU being
    powered down, therefore, remain cache-coherent throughout all PSCI
    call paths. This in turn means that PSCI cache maintenance
    operations are not required during power down.

  - Choose spin locks instead of bakery locks:

    The current PSCI implementation must synchronize both cache-coherent
    and non-cache-coherent participants. Mutual exclusion primitives are
    not guaranteed to function on non-coherent memory. For this reason,
    the current PSCI implementation had to resort to bakery locks.

    If all participants are cache-coherent, the implementation can
    enable MMU and data caches early, and substitute bakery locks for
    spin locks. Spin locks make use of architectural mutual exclusion
    primitives, and are lighter and faster.

The optimizations are applied when HW_ASSISTED_COHERENCY build option is
enabled, as it's expected that all PSCI participants are cache-coherent
in those systems.

Change-Id: Iac51c3ed318ea7e2120f6b6a46fd2db2eae46ede
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

The boolean build option HW_ASSISTED_COHERENCY is introduced to enable
various optimizations in ARM Trusted Software, when built for such
systems. It's set to 0 by default.

Change-Id: I638390da6e1718fe024dcf5b402e07084f1eb014
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Now the TRUSTED_BOARD_BOOT is supported for AArch64 when LOAD_IMAGE_V2
is enabled. This patch updates the user-guide.md documentation for the
same.

Change-Id: I97de07435c81258c2a5f41a30a69736863a10bd1
Signed-off-by: Summer Qin <summer.qin@arm.com>

This patch enables L2 ECC and Parity Protection for ARM Cortex-A57 CPUs
for Tegra SoCs.

Change-Id: I038fcd529991d0201a4951ce2730ab71b1c980f9
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

The errata is enabled by default on r0p4, which is confusing given that
we state we do not enable errata by default.

This patch clarifies this sentence by saying it is enabled in hardware
by default.

Change-Id: I70a062d93e1da2416d5f6d5776a77a659da737aa
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

The BL2 fills in the UART controller ID to be used as the normal as
well as the crash console on Tegra platforms. The controller ID to
UART controller base address mapping is handled by each Tegra SoC
the base addresses might change across Tegra chips.

This patch adds the handler to parse the platform params to get the
UART ID for the per-soc handlers.

Change-Id: I4d167b20a59aaf52a31e2a8edf94d8d6f89598fa
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

This patch adds another member, tzdram_base, to the plat_params_from_bl2 struct
in order to store the TZDRAM carveout base address used to load the Trusted OS.
The monitor programs the memory controller with the TZDRAM base and size in order
to deny any accesses from the NS world.

Change-Id: If39b8674d548175d7ccb6525c18d196ae8a8506c
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

The ARMv8v.1 architecture extension has introduced support for far
atomics, which includes compare-and-swap. Compare and Swap instruction
is only available for AArch64.

Introduce build options to choose the architecture versions to target
ARM Trusted Firmware:

  - ARM_ARCH_MAJOR: selects the major version of target ARM
    Architecture. Default value is 8.

  - ARM_ARCH_MINOR: selects the minor version of target ARM
    Architecture. Default value is 0.

When:

  (ARM_ARCH_MAJOR > 8) || ((ARM_ARCH_MAJOR == 8) && (ARM_ARCH_MINOR >= 1)),

for AArch64, Compare and Swap instruction is used to implement spin
locks. Otherwise, the implementation falls back to using
load-/store-exclusive instructions.

Update user guide, and introduce a section in Firmware Design guide to
summarize support for features introduced in ARMv8 Architecture
Extensions.

Change-Id: I73096a0039502f7aef9ec6ab3ae36680da033f16
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

This Linaro release updates both the binaries and the toolchain:
Linaro binaries upgraded 16.06 --> 16.12
AArch64 compiler upgraded 15.05 (gcc 4.9) --> 5.3-2015.05 (gcc 5.3)
AArch32 compiler upgraded 15.05 (gcc 4.9) --> 5.3-2015.05 (gcc 5.3)

The ARM TF codebase has been tested against these new binaries. This patch
updates the User Guide to reflect that the 16.12 release is now a supported
Linaro Release.

Change-Id: I6247e820f591df7d05df4f622ee45a3abf2c2d72
Signed-off-by: David Cunado <david.cunado@arm.com>

This patch introduces the following three platform interfaces:

* void plat_psci_stat_accounting_start(const psci_power_state_t *state_info)

  This is an optional hook that platforms can implement in order
  to perform accounting before entering a low power state.  This
  typically involves capturing a timestamp.

* void plat_psci_stat_accounting_stop(const psci_power_state_t *state_info)

  This is an optional hook that platforms can implement in order
  to perform accounting after exiting from a low power state.  This
  typically involves capturing a timestamp.

* u_register_t plat_psci_stat_get_residency(unsigned int lvl,
	const psci_power_state_t *state_info,
	unsigned int last_cpu_index)

  This is an optional hook that platforms can implement in order
  to calculate the PSCI stat residency.

If any of these interfaces are overridden by the platform, it is
recommended that all of them are.

By default `ENABLE_PSCI_STAT` is disabled.  If `ENABLE_PSCI_STAT`
is set but `ENABLE_PMF` is not set then an alternative PSCI stat
collection backend must be provided.  If both are set, then default
weak definitions of these functions are provided, using PMF to
calculate the residency.

NOTE: Previously, platforms did not have to explicitly set
`ENABLE_PMF` since this was automatically done by the top-level
Makefile.

Change-Id: I17b47804dea68c77bc284df15ee1ccd66bc4b79b
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

AEMv8-A Model release v8.2 has been made available and Trusted Firmware
has been tested against these versions as part of its CI system. This
patch updates the user guide documentation to reflect the version of AEM
and Cortex Models that Trusted Firmware has been tested against.

Also, the Linaro Release Notes link was broken and this patch updates the
link.

Change-Id: I88729cef909a69fff629036f480fd6168ad7dc9a
Signed-off-by: David Cunado <david.cunado@arm.com>

Introduce zeromem_dczva function on AArch64 that can handle unaligned
addresses and make use of DC ZVA instruction to zero a whole block at a
time. This zeroing takes place directly in the cache to speed it up
without doing external memory access.

Remove the zeromem16 function on AArch64 and replace it with an alias to
zeromem. This zeromem16 function is now deprecated.

Remove the 16-bytes alignment constraint on __BSS_START__ in
firmware-design.md as it is now not mandatory anymore (it used to comply
with zeromem16 requirements).

Change the 16-bytes alignment constraints in SP min's linker script to a
8-bytes alignment constraint as the AArch32 zeromem implementation is now
more efficient on 8-bytes aligned addresses.

Introduce zero_normalmem and zeromem helpers in platform agnostic header
that are implemented this way:
* AArch32:
	* zero_normalmem: zero using usual data access
	* zeromem: alias for zero_normalmem
* AArch64:
	* zero_normalmem: zero normal memory  using DC ZVA instruction
	                  (needs MMU enabled)
	* zeromem: zero using usual data access

Usage guidelines: in most cases, zero_normalmem should be preferred.

There are 2 scenarios where zeromem (or memset) must be used instead:
* Code that must run with MMU disabled (which means all memory is
  considered device memory for data accesses).
* Code that fills device memory with null bytes.

Optionally, the following rule can be applied if performance is
important:
* Code zeroing small areas (few bytes) that are not secrets should use
  memset to take advantage of compiler optimizations.

  Note: Code zeroing security-related critical information should use
  zero_normalmem/zeromem instead of memset to avoid removal by
  compilers' optimizations in some cases or misbehaving versions of GCC.

Fixes ARM-software/tf-issues#408

Change-Id: Iafd9663fc1070413c3e1904e54091cf60effaa82
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

RESET_TO_BL31=1 is specified by plat/xilinx/zynqmp/platform.mk with
"override" directive.  So, RESET_TO_BL31=1 is guaranteed without any
operation on users' side.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The errata reporting policy is as follows:

  - If an errata workaround is enabled:

    - If it applies (i.e. the CPU is affected by the errata), an INFO
      message is printed, confirming that the errata workaround has been
      applied.

    - If it does not apply, a VERBOSE message is printed, confirming
      that the errata workaround has been skipped.

  - If an errata workaround is not enabled, but would have applied had
    it been, a WARN message is printed, alerting that errata workaround
    is missing.

The CPU errata messages are printed by both BL1 (primary CPU only) and
runtime firmware on debug builds, once for each CPU/errata combination.

Relevant output from Juno r1 console when ARM Trusted Firmware is built
with PLAT=juno LOG_LEVEL=50 DEBUG=1:

  VERBOSE: BL1: cortex_a57: errata workaround for 806969 was not applied
  VERBOSE: BL1: cortex_a57: errata workaround for 813420 was not applied
  INFO:    BL1: cortex_a57: errata workaround for disable_ldnp_overread was applied
  WARNING: BL1: cortex_a57: errata workaround for 826974 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 826977 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 828024 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 829520 was missing!
  WARNING: BL1: cortex_a57: errata workaround for 833471 was missing!
  ...
  VERBOSE: BL31: cortex_a57: errata workaround for 806969 was not applied
  VERBOSE: BL31: cortex_a57: errata workaround for 813420 was not applied
  INFO:    BL31: cortex_a57: errata workaround for disable_ldnp_overread was applied
  WARNING: BL31: cortex_a57: errata workaround for 826974 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 826977 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 828024 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 829520 was missing!
  WARNING: BL31: cortex_a57: errata workaround for 833471 was missing!
  ...
  VERBOSE: BL31: cortex_a53: errata workaround for 826319 was not applied
  INFO:    BL31: cortex_a53: errata workaround for disable_non_temporal_hint was applied

Also update documentation.

Change-Id: Iccf059d3348adb876ca121cdf5207bdbbacf2aba
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

The current user guide mentions that Foundation model doesn't support
debugger interface. Clarify that all FVPs support --cadi-server option
such that a CADI-compliant debugger can connect to and control model
execution.

Also fix broken URL to FVP home page.

Change-Id: Ia14d618a4e0abb4b228eb1616040f9b51fb3f6f9
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

 - Clarify the documentation of the 'FWU_SMC_IMAGE_COPY' SMC in the
   Firmware Update guide. Also extend the list of pre-conditions to
   include the additional input validation implemented by previous
   patches.

 - Improve documentation of bl1_plat_mem_check() in the porting
   guide. It now specifies that the generic FWU code protects
   bl1_plat_mem_check() from integer overflows resulting from
   the addition of the base address and size passed in arguments.

Change-Id: I07b47a3778df7b9c089529b2dd2135707640a91c
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>

Foundation Model release 10.2 has been made available and Trusted
Firmware has been tested against that it as part of its CI system.

This patch updates the user guide documentation to reflect the version
of Foundation Model that Trusted Firmware has been tested against.

Change-Id: I8571e1027b24892b41d04b93b24245a371ca2cae
Signed-off-by: David Cunado <david.cunado@arm.com>

Various CPU drivers in ARM Trusted Firmware register functions to handle
power-down operations. At present, separate functions are registered to
power down individual cores and clusters.

This scheme operates on the basis of core and cluster, and doesn't cater
for extending the hierarchy for power-down operations. For example,
future CPUs might support multiple threads which might need powering
down individually.

This patch therefore reworks the CPU operations framework to allow for
registering power down handlers on specific level basis. Henceforth:

  - Generic code invokes CPU power down operations by the level
    required.

  - CPU drivers explicitly mention CPU_NO_RESET_FUNC when the CPU has no
    reset function.

  - CPU drivers register power down handlers as a list: a mandatory
    handler for level 0, and optional handlers for higher levels.

All existing CPU drivers are adapted to the new CPU operations framework
without needing any functional changes within.

Also update firmware design guide.

Change-Id: I1826842d37a9e60a9e85fdcee7b4b8f6bc1ad043
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>