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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>

Trusted Firmware currently has no support for secure self-hosted
debug.  To avoid unexpected exceptions, disable software debug
exceptions, other than software breakpoint instruction exceptions,
from all exception levels in secure state.  This applies to both
AArch32 and AArch64 EL3 initialization.

Change-Id: Id097e54a6bbcd0ca6a2be930df5d860d8d09e777
Signed-off-by: dp-arm <dimitris.papastamos@arm.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>

Fix the parameter type of the maintenance functions of data cache.

Add missing declarations for AArch32 versions of dcsw_op_louis and
dcsw_op_all to match the AAch64 ones.

Change-Id: I4226e8ea4f8b2b5bc2972992c83de659ee0da52c

Added the definitions `PLAT_PHY_ADDR_SPACE_SIZE` and
`PLAT_VIRT_ADDR_SPACE_SIZE` which specify respectively the physical
and virtual address space size a platform can use.

`ADDR_SPACE_SIZE` is now deprecated. To maintain compatibility, if any
of the previous defines aren't present, the value of `ADDR_SPACE_SIZE`
will be used instead.

For AArch64, register ID_AA64MMFR0_EL1 is checked to calculate the
max PA supported by the hardware and to verify that the previously
mentioned definition is valid. For AArch32, a 40 bit physical
address space is considered.

Added asserts to check for overflows.

Porting guide updated.

Change-Id: Ie8ce1da5967993f0c94dbd4eb9841fc03d5ef8d6
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch resets EL2 and EL3 registers that have architecturally
UNKNOWN values on reset and that also provide EL2/EL3 configuration
and trap controls.

Specifically, the EL2 physical timer is disabled to prevent timer
interrups into EL2 - CNTHP_CTL_EL2 and CNTHP_CTL for AArch64 and AArch32,
respectively.

Additionally, for AArch64, HSTR_EL2 is reset to avoid unexpected traps of
non-secure access to certain system registers at EL1 or lower.

For AArch32, the patch also reverts the reset to SDCR which was
incorrectly added in a previous change.

Change-Id: If00eaa23afa7dd36a922265194ccd6223187414f
Signed-off-by: David Cunado <david.cunado@arm.com>

In order to avoid unexpected traps into EL3/MON mode, this patch
resets the debug registers, MDCR_EL3 and MDCR_EL2 for AArch64,
and SDCR and HDCR for AArch32.

MDCR_EL3/SDCR is zero'ed when EL3/MON mode is entered, at the
start of BL1 and BL31/SMP_MIN.

For MDCR_EL2/HDCR, this patch zero's the bits that are
architecturally UNKNOWN values on reset. This is done when
exiting from EL3/MON mode but only on platforms that support
EL2/HYP mode but choose to exit to EL1/SVC mode.

Fixes ARM-software/tf-issues#430

Change-Id: Idb992232163c072faa08892251b5626ae4c3a5b6
Signed-off-by: David Cunado <david.cunado@arm.com>

The values of CP15BEN, nTWI & nTWE bits in SCTLR_EL1 are architecturally
unknown if EL3 is AARCH64 whereas they reset to 1 if EL3 is AArch32. This
might be a compatibility break for legacy AArch32 normal world software if
these bits are not set to 1 when EL3 is AArch64. This patch enables the
CP15BEN, nTWI and nTWE bits in the SCTLR_EL1 if the lower non-secure EL is
AArch32. This unifies the SCTLR settings for lower non-secure EL in AArch32
mode for both AArch64 and AArch32 builds of Trusted Firmware.

Fixes ARM-software/tf-issues#428

Change-Id: I3152d1580e4869c0ea745c5bd9da765f9c254947
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

This patch support single core to boot to Linux kernel
through Trusted Firmware.
It also support 32 bit kernel and 64 bit kernel booting.

Instead of hardcoding a level 1 table as the base translation level
table, let the code decide which level is the most appropriate given
the virtual address space size.

As the table granularity is 4 KB, this allows the code to select
level 0, 1 or 2 as base level for AArch64. This way, instead of
limiting the virtual address space width to 39-31 bits, widths of
48-25 bit can be used.

For AArch32, this change allows the code to select level 1 or 2
as the base translation level table and use virtual address space
width of 32-25 bits.

Also removed some unused definitions related to translation tables.

Fixes ARM-software/tf-issues#362

Change-Id: Ie3bb5d6d1a4730a26700b09827c79f37ca3cdb65

This patch adds an API in runtime service framework to
invoke the registered handler corresponding to the SMC function
identifier. This is helpful for AArch32 because the number of
arguments required by the handler is more than registers
available as per AArch32 program calling conventions and
requires the use of stack. Hence this new API will do the
necessary argument setup and invoke the appropriate
handler. Although this API is primarily intended for AArch32,
it can be used for AArch64 as well.

Change-Id: Iefa15947fe5a1df55b0859886e677446a0fd7241

This patch moves the macro SIZE_FROM_LOG2_WORDS() defined in
`arch.h` to `utils.h` as it is utility macro.

Change-Id: Ia8171a226978f053a1ee4037f80142c0a4d21430

This patch introduces the PSCI Library interface. The major changes
introduced are as follows:

* Earlier BL31 was responsible for Architectural initialization during cold
boot via bl31_arch_setup() whereas PSCI was responsible for the same during
warm boot. This functionality is now consolidated by the PSCI library
and it does Architectural initialization via psci_arch_setup() during both
cold and warm boots.

* Earlier the warm boot entry point was always `psci_entrypoint()`. This was
not flexible enough as a library interface. Now PSCI expects the runtime
firmware to provide the entry point via `psci_setup()`. A new function
`bl31_warm_entrypoint` is introduced in BL31 and the previous
`psci_entrypoint()` is deprecated.

* The `smc_helpers.h` is reorganized to separate the SMC Calling Convention
defines from the Trusted Firmware SMC helpers. The former is now in a new
header file `smcc.h` and the SMC helpers are moved to Architecture specific
header.

* The CPU context is used by PSCI for context initialization and
restoration after power down (PSCI Context). It is also used by BL31 for SMC
handling and context management during Normal-Secure world switch (SMC
Context). The `psci_smc_handler()` interface is redefined to not use SMC
helper macros thus enabling to decouple the PSCI context from EL3 runtime
firmware SMC context. This enables PSCI to be integrated with other runtime
firmware using a different SMC context.

NOTE: With this patch the architectural setup done in `bl31_arch_setup()`
is done as part of `psci_setup()` and hence `bl31_platform_setup()` will be
invoked prior to architectural setup. It is highly unlikely that the platform
setup will depend on architectural setup and cause any failure. Please be
be aware of this change in sequence.

Change-Id: I7f497a08d33be234bbb822c28146250cb20dab73

The AArch32 long descriptor format and the AArch64 descriptor format
correspond to each other which allows possible sharing of xlat_tables
library code between AArch64 and AArch32. This patch refactors the
xlat_tables library code to seperate the common functionality from
architecture specific code. Prior to this patch, all of the xlat_tables
library code were in `lib/aarch64/xlat_tables.c` file. The refactored code
is now in `lib/xlat_tables/` directory. The AArch64 specific programming
for xlat_tables is in `lib/xlat_tables/aarch64/xlat_tables.c` and the rest
of the code common to AArch64 and AArch32 is in
`lib/xlat_tables/xlat_tables_common.c`. Also the data types used in
xlat_tables library APIs are reworked to make it compatible between AArch64
and AArch32.

The `lib/aarch64/xlat_tables.c` file now includes the new xlat_tables
library files to retain compatibility for existing platform ports.
The macros related to xlat_tables library are also moved from
`include/lib/aarch64/arch.h` to the header `include/lib/xlat_tables.h`.

NOTE: THE `lib/aarch64/xlat_tables.c` FILE IS DEPRECATED AND PLATFORM PORTS
ARE EXPECTED TO INCLUDE THE NEW XLAT_TABLES LIBRARY FILES IN THEIR MAKEFILES.

Change-Id: I3d17217d24aaf3a05a4685d642a31d4d56255a0f

lib/aarch64/xlat_helpers.c defines helper functions to build
translation descriptors, but no common code or upstream platform
port uses them. As the rest of the xlat_tables code evolves, there
may be conflicts with these helpers, therefore this code should be
removed.

Change-Id: I9f5be99720f929264818af33db8dada785368711

Bring ISR bits definition as a mnemonic for troublershooters as well.
Signed-off-by: Gerald Lejeune <gerald.lejeune@st.com>

These macros are unused and redundant with other CPU system registers
functions.

Moreover enable_serror() function implementation may not reach its purpose
because it does not handle the value of SCR_EL3.EA.
Signed-off-by: Gerald Lejeune <gerald.lejeune@st.com>

At the moment, the memory translation library allows to create memory
mappings of 2 types:

 - Device nGnRE memory (named MT_DEVICE in the library);

 - Normal, Inner Write-back non-transient, Outer Write-back
   non-transient memory (named MT_MEMORY in the library).

As a consequence, the library code treats the memory type field as a
boolean: everything that is not device memory is normal memory and
vice-versa.

In reality, the ARMv8 architecture allows up to 8 types of memory to
be used at a single time for a given exception level. This patch
reworks the memory attributes such that the memory type is now defined
as an integer ranging from 0 to 7 instead of a boolean. This makes it
possible to extend the list of memory types supported by the memory
translation library.

The priority system dictating memory attributes for overlapping
memory regions has been extended to cope with these changes but the
algorithm at its core has been preserved. When a memory region is
re-mapped with different memory attributes, the memory translation
library examines the former attributes and updates them only if
the new attributes create a more restrictive mapping. This behaviour
is unchanged, only the manipulation of the value has been modified
to cope with the new format.

This patch also introduces a new type of memory mapping in the memory
translation library: MT_NON_CACHEABLE, meaning Normal, Inner
Non-cacheable, Outer Non-cacheable memory. This can be useful to map
a non-cacheable memory region, such as a DMA buffer for example.

The rules around the Execute-Never (XN) bit in a translation table
for an MT_NON_CACHEABLE memory mapping have been aligned on the rules
used for MT_MEMORY mappings:
 - If the memory is read-only then it is also executable (XN = 0);
 - If the memory is read-write then it is not executable (XN = 1).

The shareability field for MT_NON_CACHEABLE mappings is always set as
'Outer-Shareable'. Note that this is not strictly needed since
shareability is only relevant if the memory is a Normal Cacheable
memory type, but this is to align with the existing device memory
mappings setup. All Device and Normal Non-cacheable memory regions
are always treated as Outer Shareable, regardless of the translation
table shareability attributes.

This patch also removes the 'ATTR_SO' and 'ATTR_SO_INDEX' #defines.
They were introduced to map memory as Device nGnRnE (formerly called
"Strongly-Ordered" memory in the ARMv7 architecture) but were not
used anywhere in the code base. Removing them avoids any confusion
about the memory types supported by the library.

Upstream platforms do not currently use the MT_NON_CACHEABLE memory
type.

NOTE: THIS CHANGE IS SOURCE COMPATIBLE BUT PLATFORMS THAT RELY ON THE
BINARY VALUES OF `mmap_attr_t` or the `attr` argument of
`mmap_add_region()` MAY BE BROKEN.

Change-Id: I717d6ed79b4c845a04e34132432f98b93d661d79

The shared memory region on ARM platforms contains the mailboxes and,
on Juno, the payload area for communication with the SCP. This shared
memory may be configured as normal memory or device memory at build
time by setting the platform flag 'PLAT_ARM_SHARED_RAM_CACHED' (on
Juno, the value of this flag is defined by 'MHU_PAYLOAD_CACHED').
When set as normal memory, the platform port performs the corresponding
cache maintenance operations. From a functional point of view, this is
the equivalent of setting the shared memory as device memory, so there
is no need to maintain both options.

This patch removes the option to specify the shared memory as normal
memory on ARM platforms. Shared memory is always treated as device
memory. Cache maintenance operations are no longer needed and have
been replaced by data memory barriers to guarantee that payload and
MHU are accessed in the right order.

Change-Id: I7f958621d6a536dd4f0fa8768385eedc4295e79f

In the situation that EL1 is selected as the exception level for the
next image upon BL31 exit for a processor that supports EL2, the
context management code must configure all essential EL2 register
state to ensure correct execution of EL1.

VTTBR_EL2 should be part of this set of EL2 registers because:
 - The ARMv8-A architecture does not define a reset value for this
   register.
 - Cache maintenance operations depend on VTTBR_EL2.VMID even when
   non-secure EL1&0 stage 2 address translation are disabled.

This patch initializes the VTTBR_EL2 register to 0 when bypassing EL2
to address this issue. Note that this bug has not yet manifested
itself on FVP or Juno because VTTBR_EL2.VMID resets to 0 on the
Cortex-A53 and Cortex-A57.

Change-Id: I58ce2d16a71687126f437577a506d93cb5eecf33

This patch adds a driver for ARM GICv3 systems that need to run software
stacks where affinity routing is enabled across all privileged exception
levels for both security states. This driver is a partial implementation
of the ARM Generic Interrupt Controller Architecture Specification, GIC
architecture version 3.0 and version 4.0 (ARM IHI 0069A). The driver does
not cater for legacy support of interrupts and asymmetric configurations.

The existing GIC driver has been preserved unchanged. The common code for
GICv2 and GICv3 systems has been refactored into a new file,
`drivers/arm/gic/common/gic_common.c`. The corresponding header is in
`include/drivers/arm/gic_common.h`.

The driver interface is implemented in `drivers/arm/gic/v3/gicv3_main.c`.
The corresponding header is in `include/drivers/arm/gicv3.h`. Helper
functions are implemented in `drivers/arm/gic/v3/arm_gicv3_helpers.c`
and are accessible through the `drivers/arm/gic/v3/gicv3_private.h`
header.

Change-Id: I8c3c834a1d049d05b776b4dcb76b18ccb927444a

As per Section D7.2.81 in the ARMv8-A Reference Manual (DDI0487A Issue A.h),
bits[29:28], bits[23:22], bit[20] and bit[11] in the SCTLR_EL1 are RES1. This
patch adds the missing bit[20] to the SCTLR_EL1_RES1 macro.

Change-Id: I827982fa2856d04def6b22d8200a79fe6922a28e

On the ARMv8 architecture, cache maintenance operations by set/way on the last
level of integrated cache do not affect the system cache. This means that such a
flush or clean operation could result in the data being pushed out to the system
cache rather than main memory. Another CPU could access this data before it
enables its data cache or MMU. Such accesses could be serviced from the main
memory instead of the system cache. If the data in the sysem cache has not yet
been flushed or evicted to main memory then there could be a loss of
coherency. The only mechanism to guarantee that the main memory will be updated
is to use cache maintenance operations to the PoC by MVA(See section D3.4.11
(System level caches) of ARMv8-A Reference Manual (Issue A.g/ARM DDI0487A.G).

This patch removes the reliance of Trusted Firmware on the flush by set/way
operation to ensure visibility of data in the main memory. Cache maintenance
operations by MVA are now used instead. The following are the broad category of
changes:

1. The RW areas of BL2/BL31/BL32 are invalidated by MVA before the C runtime is
   initialised. This ensures that any stale cache lines at any level of cache
   are removed.

2. Updates to global data in runtime firmware (BL31) by the primary CPU are made
   visible to secondary CPUs using a cache clean operation by MVA.

3. Cache maintenance by set/way operations are only used prior to power down.

NOTE: NON-UPSTREAM TRUSTED FIRMWARE CODE SHOULD MAKE EQUIVALENT CHANGES IN
ORDER TO FUNCTION CORRECTLY ON PLATFORMS WITH SUPPORT FOR SYSTEM CACHES.

Fixes ARM-software/tf-issues#205

Change-Id: I64f1b398de0432813a0e0881d70f8337681f6e9a

The required platform constant PLATFORM_CACHE_LINE_SIZE is
unnecessary since CACHE_WRITEBACK_GRANULE effectively provides the
same information. CACHE_WRITEBACK_GRANULE is preferred since this
is an architecturally defined term and allows comparison with the
corresponding hardware register value.

Replace all usage of PLATFORM_CACHE_LINE_SIZE with
CACHE_WRITEBACK_GRANULE.

Also, add a runtime assert in BL1 to check that the provided
CACHE_WRITEBACK_GRANULE matches the value provided in CTR_EL0.

Change-Id: If87286be78068424217b9f3689be358356500dcd

This patch adds functionality to translate virtual addresses from
secure or non-secure worlds. This functionality helps Trusted Apps
to share virtual addresses directly and allows the NS world to
pass virtual addresses to TLK directly.

Change-Id: I77b0892963e0e839c448b5d0532920fb7e54dc8e
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

This patch updates the FVP and Juno platform ports to use the common
driver for ARM Cache Coherent Interconnects.

Change-Id: Ib142f456b9b673600592616a2ec99e9b230d6542

This patch adds support to return SUCCESS if a pending interrupt is
detected during a CPU_SUSPEND call to a power down state. The check
is performed as late as possible without losing the ability to return
to the caller. This reduces the overhead incurred by a CPU in
undergoing a complete power cycle when a wakeup interrupt is already
pending.

Fixes ARM-Software/tf-issues#102

Change-Id: I1aff04a74b704a2f529734428030d1d10750fd4b

This patch adds helper macros for barrier operations that specify
the type of barrier (dmb, dsb) and the shareability domain (system,
inner-shareable) it affects.

Change-Id: I4bf95103e79da212c4fbdbc13d91ad8ac385d9f5

Calls to system register read accessors functions may be optimised
out by the compiler if called twice in a row for the same register.
This is because the compiler is not aware that the result from
the instruction may be modified by external agents. Therefore, if
nothing modifies the register between the 2 reads as far as the
compiler knows then it might consider that it is useless to read
it twice and emit only 1 call.

This behaviour is faulty for registers that may not have the same
value if read twice in succession. E.g.: counters, timer
control/countdown registers, GICv3 interrupt status registers and
so on.

The same problem happens for calls to system register write
accessors functions. The compiler might optimise out some calls
if it considers that it will produce the same result. Again, this
behaviour is faulty for cases where intermediate writes to these
registers make a difference in the system.

This patch fixes the problem by making these assembly register
accesses volatile.

Fixes ARM-software/tf-issues#273

Change-Id: I33903bc4cc4eea8a8d87bc2c757909fbb0138925

This patch fixes the array size of mpidr_aff_map_nodes_t which
was less by one element.

Fixes ARM-software/tf-issues#264

Change-Id: I48264f6f9e7046a3d0f4cbcd63b9ba49657e8818

Prior to this patch, the errata workarounds were applied for any version
of the CPU in the release build and in the debug build an assert
failure resulted when the revision did not match. This patch applies
errata workarounds in the Cortex-A57 reset handler only if the 'variant'
and 'revision' fields read from the MIDR_EL1 match. In the debug build,
a warning message is printed for each errata workaround which is not
applied.

The patch modifies the register usage in 'reset_handler` so
as to adhere to ARM procedure calling standards.

Fixes ARM-software/tf-issues#242

Change-Id: I51b1f876474599db885afa03346e38a476f84c29

This patch uses the IMAGE_BL<x> constants to create translation tables specific
to a boot loader stage. This allows each stage to create mappings only for areas
in the memory map that it needs.

Fixes ARM-software/tf-issues#209

Change-Id: Ie4861407ddf9317f0fb890fc7575eaa88d0de51c

Initializes SCTLR_EL1 based on MODE_RW bit in SPSR for the entry
point. The RES1 bits for SCTLR_EL1 differs for Aarch64 and Aarch32
mode.

This patch resets the value of CNTVOFF_EL2 before exit to EL1 on
warm boot. This needs to be done if only the Trusted Firmware exits
to EL1 instead of EL2, otherwise the hypervisor would be responsible
for this.

Fixes ARM-software/tf-issues#240

Change-Id: I79d54831356cf3215bcf1f251c373bd8f89db0e0

This patch adds the initial port of the ARM Trusted Firmware on the Juno
development platform. This port does not support a BL3-2 image or any PSCI APIs
apart from PSCI_VERSION and PSCI_CPU_ON. It enables workarounds for selected
Cortex-A57 (#806969 & #813420) errata and implements the workaround for a Juno
platform errata (Defect id 831273).

Change-Id: Ib3d92df3af53820cfbb2977582ed0d7abf6ef893

This patch adds workarounds for selected errata which affect the Cortex-A57 r0p0
part. Each workaround has a build time flag which should be used by the platform
port to enable or disable the corresponding workaround. The workarounds are
disabled by default. An assertion is raised if the platform enables a workaround
which does not match the CPU revision at runtime.

Change-Id: I9ae96b01c6ff733d04dc733bd4e67dbf77b29fb0

This patch adds handlers for dumping Cortex-A57 and Cortex-A53 specific register
state to the CPU specific operations framework. The contents of CPUECTLR_EL1 are
dumped currently.

Change-Id: I63d3dbfc4ac52fef5e25a8cf6b937c6f0975c8ab

This patch adds CPU core and cluster power down sequences to the CPU specific
operations framework introduced in a earlier patch. Cortex-A53, Cortex-A57 and
generic AEM sequences have been added. The latter is suitable for the
Foundation and Base AEM FVPs. A pointer to each CPU's operations structure is
saved in the per-cpu data so that it can be easily accessed during power down
seqeunces.

An optional platform API has been introduced to allow a platform to disable the
Accelerator Coherency Port (ACP) during a cluster power down sequence. The weak
definition of this function (plat_disable_acp()) does not take any action. It
should be overriden with a strong definition if the ACP is present on a
platform.

Change-Id: I8d09bd40d2f528a28d2d3f19b77101178778685d

This patch introduces a framework which will allow CPUs to perform
implementation defined actions after a CPU reset, during a CPU or cluster power
down, and when a crash occurs. CPU specific reset handlers have been implemented
in this patch. Other handlers will be implemented in subsequent patches.

Also moved cpu_helpers.S to the new directory lib/cpus/aarch64/.

Change-Id: I1ca1bade4d101d11a898fb30fea2669f9b37b956