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NOTE: AARCH32/AARCH64 macros are now deprecated in favor of __aarch64__.

All common C compilers pre-define the same macros to signal which
architecture the code is being compiled for: __arm__ for AArch32 (or
earlier versions) and __aarch64__ for AArch64. There's no need for TF-A
to define its own custom macros for this. In order to unify code with
the export headers (which use __aarch64__ to avoid another dependency),
let's deprecate the AARCH32 and AARCH64 macros and switch the code base
over to the pre-defined standard macro. (Since it is somewhat
unintuitive that __arm__ only means AArch32, let's standardize on only
using __aarch64__.)

Change-Id: Ic77de4b052297d77f38fc95f95f65a8ee70cf200
Signed-off-by: Julius Werner <jwerner@chromium.org>

Use full include paths like it is done for common includes.

This cleanup was started in commit d40e0e08283a ("Sanitise includes
across codebase"), but it only cleaned common files and drivers. This
patch does the same to Arm platforms.

Change-Id: If982e6450bbe84dceb56d464e282bcf5d6d9ab9b
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

From now on, platform_def.h must include any header with definitions that
are platform-specific (like arm_def.h) and the included headers mustn't
include back platform_def.h, and shouldn't be used by other files. Only
platform_def.h should be included in other files. This will ensure that all
needed definitions are present, rather than needing to include all the
headers in all the definitions' headers just in case.

This also prevents problems like cyclic dependencies.

Change-Id: I9d3cf4d1de4b956fa035c79545222697acdaf5ca
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Enforce full include path for includes. Deprecate old paths.

The following folders inside include/lib have been left unchanged:

- include/lib/cpus/${ARCH}
- include/lib/el3_runtime/${ARCH}

The reason for this change is that having a global namespace for
includes isn't a good idea. It defeats one of the advantages of having
folders and it introduces problems that are sometimes subtle (because
you may not know the header you are actually including if there are two
of them).

For example, this patch had to be created because two headers were
called the same way: e0ea0928 ("Fix gpio includes of mt8173 platform
to avoid collision."). More recently, this patch has had similar
problems: 46f9b2c3 ("drivers: add tzc380 support").

This problem was introduced in commit 4ecca339

 ("Move include and
source files to logical locations"). At that time, there weren't too
many headers so it wasn't a real issue. However, time has shown that
this creates problems.

Platforms that want to preserve the way they include headers may add the
removed paths to PLAT_INCLUDES, but this is discouraged.

Change-Id: I39dc53ed98f9e297a5966e723d1936d6ccf2fc8f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

In order to allow Arm platforms to override the default list of PSCI
callbacks, remove the existing weak implementation of
'plat_arm_psci_override_pm_ops' function and let all the Arm platforms
implement their own 'plat_arm_psci_override_pm_ops' function.

For platforms that support SCMI protocol, the function
'css_scmi_override_pm_ops' can be additionally used as well to
override the default PSCI callbacks.

Change-Id: If7c27468bd51a00ea9c2a3716b5894163f5a9f3c
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>

Change-Id: Ia00eba2b18804e6498d935d33ec104953e0e5e03
Signed-off-by: Sathees Balya <sathees.balya@arm.com>

Mark the initialization functions found in the BL31 boot sequence
as __init so they can be reclaimed when no longer needed.

Change-Id: I687a89346419c7710ef5097feaa325d83c527697
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>

- Remove references to removed build options.
- Remove support for legacy GIC driver.
- Remove support for LOAD_IMAGE_V2=0.

Change-Id: I72f8c05620bdf4a682765e6e53e2c04ca749a3d5
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This also gets rid of MISRA violations for Rule 8.3 and 8.4.

Change-Id: I45bba011b16f90953dd4b260fcd58381f978eedc
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Fix violations of MISRA C-2012 Rules 10.1, 10.3, 13.3, 14.4, 17.7 and
17.8.

Change-Id: I6c9725e428b5752f1d80684ec29cb6c52a5c0c2d
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Change-Id: Iaebbeac1a1d6fbd531e5694b95ed068b7a193e62
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>

The plat_arm_mmap variable is already declared in plat_arm.h, which is
included from plat/arm/common/arm_common.c.

Similarly, plat_arm.h declares the 'plat_arm_psci_pm_ops' variable, which
does not need to be declared again in plat/arm/common/arm_pm.c.

The duplication was not compliant with MISRA rule 8.5.

Change-Id: Icc42547cc025023226b1078a7ec4f06d093364b7
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>

The old API is deprecated and will eventually be removed.

Arm platforms now use the multi console driver for boot and runtime
consoles. However, the crash console uses the direct console API because
it doesn't need any memory access to work. This makes it more robust
during crashes.

The AArch32 port of the Trusted Firmware doesn't support this new API
yet, so it is only enabled in AArch64 builds. Because of this, the
common code must maintain compatibility with both systems. SP_MIN
doesn't have to be updated because it's only used in AArch32 builds.
The TSP is only used in AArch64, so it only needs to support the new
API without keeping support for the old one.

Special care must be taken because of PSCI_SYSTEM_SUSPEND. In Juno, this
causes the UARTs to reset (except for the one used by the TSP). This
means that they must be unregistered when suspending and re-registered
when resuming. This wasn't a problem with the old driver because it just
restarted the UART, and there were no problems associated with
registering and unregistering consoles.

The size reserved for BL2 has been increased.

Change-Id: Icefd117dd1eb9c498921181a21318c2d2435c441
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This reverts commit 2f18aa1f

.

It is causing some tests to fail. Until the cause is found and fixed, it
is needed to remove this commit from master.

Change-Id: Ic5ff7a841903a15613e00379e87cbbd8a0e85152
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

The old API is deprecated and will eventually be removed.

Arm platforms now use the multi console driver for boot and runtime
consoles. However, the crash console uses the direct console API because
it doesn't need any memory access to work. This makes it more robust
during crashes.

The AArch32 port of the Trusted Firmware doesn't support this new API
yet, so it is only enabled in AArch64 builds. Because of this, the
common code must maintain compatibility with both systems. SP_MIN
doesn't have to be updated because it's only used in AArch32 builds.
The TSP is only used in AArch64, so it only needs to support the new
API without keeping support for the old one.

Special care must be taken because of PSCI_SYSTEM_SUSPEND. In Juno, this
causes the UARTs to reset (except for the one used by the TSP). This
means that they must be unregistered when suspending and re-registered
when resuming. This wasn't a problem with the old driver because it just
restarted the UART, and there were no problems associated with
registering and unregistering consoles.

The size of BL31 has been increased in builds with SPM.

Change-Id: Icefd117dd1eb9c498921181a21318c2d2435c441
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

The function arm_validate_ns_entrypoint() validates a given non-secure
physical address. This function however specifically returns PSCI error
codes.

Non-secure physical address validation is potentially useful across ARM
platforms, even for non-PSCI use cases. Therefore make this function
common by returning 0 for success or -1 otherwise.

Having made the function common, make arm_validate_psci_entrypoint() a
wrapper around arm_validate_ns_entrypoint() which only translates return
value into PSCI error codes. This wrapper is now used where
arm_validate_ns_entrypoint() was currently used for PSCI entry point
validation.

Change-Id: Ic781fc3105d6d199fd8f53f01aba5baea0ebc310
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Provides GICv3 save/restore feature to arm_system_pwr_domain_resume and
arm_system_pwr_domain_save functions.

Introduce FVP PSCI power level 3 (System level) support. This is solely
done to provide example code on how to use the GICv3 save and restore
helpers.

Also make CSS GICv3 platforms power off the Redistributor on SYSTEM
SUSPEND as its state is saved and restored.

Change-Id: I0d852f3af8824edee1a17c085cf593ddd33a4e77
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Co-Authored-by: Douglas Raillard <douglas.raillard@arm.com>

Since ARM_DRAM2_BASE is above the 32-bit limit, the condition
is always false.  Wrap this condition in an ifndef to avoid
warnings during compilation.

Change-Id: Ideabb6c65de6c62474ed03eb29df4b049d5316be
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.

NOTE: Files that have been imported by FreeBSD have not been modified.

[0]: https://spdx.org/



Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

The capabilities exposed by the PSCI generic layer depends on the hooks
populated by the platform in `plat_arm_psci_pm_ops`. Currently ARM
Standard platforms statically define this structure. However, some
platforms may want to modify the hooks at runtime before registering
them with the generic layer.

This patch introduces a new ARM platform layer API
`plat_arm_psci_override_pm_ops` which allows the platform to probe
the power controller and modify `plat_arm_psci_pm_ops` if required.
Consequently, 'plat_arm_psci_pm_ops' is no longer qualified as
`const` on ARM Standard platforms.

Change-Id: I7dbb44b7bd36c20ec14ded5ee45a96816ca2ab9d
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

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

This patch overrides the default weak definition of
`bl31_plat_runtime_setup()` for ARM Standard platforms to
specify a BL31 runtime console. ARM Standard platforms are
now expected to define `PLAT_ARM_BL31_RUN_UART_BASE` and
`PLAT_ARM_BL31_RUN_UART_CLK_IN_HZ` macros which is required
by `arm_bl31_plat_runtime_setup()` to initialize the runtime
console.

The system suspend resume helper `arm_system_pwr_domain_resume()`
is fixed to initialize the runtime console rather than the boot
console on resumption from system suspend.

Fixes ARM-software/tf-issues#220

Change-Id: I80eafe5b6adcfc7f1fdf8b99659aca1c64d96975

Suport for ARM GIC v2.0 and v3.0 drivers has been reworked to create three
separate drivers instead of providing a single driver that can work on both
versions of the GIC architecture. These drivers correspond to the following
software use cases:

1. A GICv2 only driver that can run only on ARM GIC v2.0 implementations
   e.g. GIC-400

2. A GICv3 only driver that can run only on ARM GIC v3.0 implementations
   e.g. GIC-500 in a mode where all interrupt regimes use GICv3 features

3. A deprecated GICv3 driver that operates in legacy mode. This driver can
   operate only in the GICv2 mode in the secure world. On a GICv3 system, this
   driver allows normal world to run in either GICv3 mode (asymmetric mode)
   or in the GICv2 mode. Both modes of operation are deprecated on GICv3
   systems.

ARM platforms implement both versions of the GIC architecture. This patch adds a
layer of abstraction to help ARM platform ports chose the right GIC driver and
corresponding platform support. This is as described below:

1. A set of ARM common functions have been introduced to initialise the GIC and
   the driver during cold and warm boot. These functions are prefixed as
   "plat_arm_gic_". Weak definitions of these functions have been provided for
   each type of driver.

2. Each platform includes the sources that implement the right functions
   directly into the its makefile. The FVP can be instantiated with different
   versions of the GIC architecture. It uses the FVP_USE_GIC_DRIVER build option
   to specify which of the three drivers should be included in the build.

3. A list of secure interrupts has to be provided to initialise each of the
  three GIC drivers. For GIC v3.0 the interrupt ids have to be further
  categorised as Group 0 and Group 1 Secure interrupts. For GIC v2.0, the two
  types are merged and treated as Group 0 interrupts.

  The two lists of interrupts are exported from the platform_def.h. The lists
  are constructed by adding a list of board specific interrupt ids to a list of
  ids common to all ARM platforms and Compute sub-systems.

This patch also makes some fields of `arm_config` data structure in FVP redundant
and these unused fields are removed.

Change-Id: Ibc8c087be7a8a6b041b78c2c3bd0c648cd2035d8

This patch adds support for booting EL3 payloads on CSS platforms,
for example Juno. In this scenario, the Trusted Firmware follows
its normal boot flow up to the point where it would normally pass
control to the BL31 image. At this point, it jumps to the EL3
payload entry point address instead.

Before handing over to the EL3 payload, the data SCP writes for AP
at the beginning of the Trusted SRAM is restored, i.e. we zero the
first 128 bytes and restore the SCP Boot configuration. The latter
is saved before transferring the BL30 image to SCP and is restored
just after the transfer (in BL2). The goal is to make it appear that
the EL3 payload is the first piece of software to run on the target.

The BL31 entrypoint info structure is updated to make the primary
CPU jump to the EL3 payload instead of the BL31 image.

The mailbox is populated with the EL3 payload entrypoint address,
which releases the secondary CPUs out of their holding pen (if the
SCP has powered them on). The arm_program_trusted_mailbox() function
has been exported for this purpose.

The TZC-400 configuration in BL2 is simplified: it grants secure
access only to the whole DRAM. Other security initialization is
unchanged.

This alternative boot flow is disabled by default. A new build option
EL3_PAYLOAD_BASE has been introduced to enable it and provide the EL3
payload's entry point address. The build system has been modified
such that BL31 and BL33 are not compiled and/or not put in the FIP in
this case, as those images are not used in this boot flow.

Change-Id: Id2e26fa57988bbc32323a0effd022ab42f5b5077

This patch adds the capability to power down at system power domain level
on Juno via the PSCI SYSTEM SUSPEND API. The CSS power management helpers
are modified to add support for power management operations at system
power domain level. A new helper for populating `get_sys_suspend_power_state`
handler in plat_psci_ops is defined. On entering the system suspend state,
the SCP powers down the SYSTOP power domain on the SoC and puts the memory
into retention mode. On wakeup from the power down, the system components
on the CSS will be reinitialized by the platform layer and the PSCI client
is responsible for restoring the context of these system components.

According to PSCI Specification, interrupts targeted to cores in PSCI CPU
SUSPEND should be able to resume it. On Juno, when the system power domain
is suspended, the GIC is also powered down. The SCP resumes the final core
to be suspend when an external wake-up event is received. But the other
cores cannot be woken up by a targeted interrupt, because GIC doesn't
forward these interrupts to the SCP. Due to this hardware limitation,
we down-grade PSCI CPU SUSPEND requests targeted to the system power domain
level to cluster power domain level in `juno_validate_power_state()`
and the CSS default `plat_arm_psci_ops` is overridden in juno_pm.c.

A system power domain resume helper `arm_system_pwr_domain_resume()` is
defined for ARM standard platforms which resumes/re-initializes the
system components on wakeup from system suspend. The security setup also
needs to be done on resume from system suspend, which means
`plat_arm_security_setup()` must now be included in the BL3-1 image in
addition to previous BL images if system suspend need to be supported.

Change-Id: Ie293f75f09bad24223af47ab6c6e1268f77bcc47

This patch does the following reorganization to psci power management (PM)
handler setup for ARM standard platform ports :

1. The mailbox programming required during `plat_setup_psci_ops()` is identical
   for all ARM platforms. Hence the implementation of this API is now moved
   to the common `arm_pm.c` file. Each ARM platform now must define the
   PLAT_ARM_TRUSTED_MAILBOX_BASE macro, which in current platforms is the same
   as ARM_SHARED_RAM_BASE.

2. The PSCI PM handler callback structure, `plat_psci_ops`, must now be
   exported via `plat_arm_psci_pm_ops`. This allows the common implementation
   of `plat_setup_psci_ops()` to return a platform specific `plat_psci_ops`.
   In the case of CSS platforms, a default weak implementation of the same is
   provided in `css_pm.c` which can be overridden by each CSS platform.

3. For CSS platforms, the PSCI PM handlers defined in `css_pm.c` are now
   made library functions and a new header file `css_pm.h` is added to export
   these generic PM handlers. This allows the platform to reuse the
   adequate CSS PM handlers and redefine others which need to be customized
   when overriding the default `plat_arm_psci_pm_ops` in `css_pm.c`.

Change-Id: I277910f609e023ee5d5ff0129a80ecfce4356ede

This patch implements the platform power managment handler to verify
non secure entrypoint for ARM platforms. The handler ensures that the
entry point specified by the normal world during CPU_SUSPEND, CPU_ON
or SYSTEM_SUSPEND PSCI API is a valid address within the non secure
DRAM.

Change-Id: I4795452df99f67a24682b22f0e0967175c1de429

This patch adds support to the Juno and FVP ports for composite power states
with both the original and extended state-id power-state formats. Both the
platform ports use the recommended state-id encoding as specified in
Section 6.5 of the PSCI specification (ARM DEN 0022C). The platform build flag
ARM_RECOM_STATE_ID_ENC is used to include this support.

By default, to maintain backwards compatibility, the original power state
parameter format is used and the state-id field is expected to be zero.

Change-Id: Ie721b961957eaecaca5bf417a30952fe0627ef10

This patch migrates ARM reference platforms, Juno and FVP, to the new platform
API mandated by the new PSCI power domain topology and composite power state
frameworks. The platform specific makefiles now exports the build flag
ENABLE_PLAT_COMPAT=0 to disable the platform compatibility layer.

Change-Id: I3040ed7cce446fc66facaee9c67cb54a8cd7ca29

This major change pulls out the common functionality from the
FVP and Juno platform ports into the following categories:

*   (include/)plat/common. Common platform porting functionality that
typically may be used by all platforms.

*   (include/)plat/arm/common. Common platform porting functionality
that may be used by all ARM standard platforms. This includes all
ARM development platforms like FVP and Juno but may also include
non-ARM-owned platforms.

*   (include/)plat/arm/board/common. Common platform porting
functionality for ARM development platforms at the board
(off SoC) level.

*   (include/)plat/arm/css/common. Common platform porting
functionality at the ARM Compute SubSystem (CSS) level. Juno
is an example of a CSS-based platform.

*   (include/)plat/arm/soc/common. Common platform porting
functionality at the ARM SoC level, which is not already defined
at the ARM CSS level.

No guarantees are made about the backward compatibility of
functionality provided in (include/)plat/arm.

Also remove any unnecessary variation between the ARM development
platform ports, including:

*   Unify the way BL2 passes `bl31_params_t` to BL3-1. Use the
Juno implementation, which copies the information from BL2 memory
instead of expecting it to persist in shared memory.

*   Unify the TZC configuration. There is no need to add a region
for SCP in Juno; it's enough to simply not allow any access to
this reserved region. Also set region 0 to provide no access by
default instead of assuming this is the case.

*   Unify the number of memory map regions required for ARM
development platforms, although the actual ranges mapped for each
platform may be different. For the FVP port, this reduces the
mapped peripheral address space.

These latter changes will only be observed when the platform ports
are migrated to use the new common platform code in subsequent
patches.

Change-Id: Id9c269dd3dc6e74533d0e5116fdd826d53946dc8

TLK Dispatcher (tlkd) is based on the tspd and is the glue required
to run TLK as a Secure Payload with the Trusted Firmware.

Change-Id: I69e573d26d52342eb049feef773dd7d2a506f4ab
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

This patch disables routing of external aborts from lower exception levels to
EL3 and ensures that a SError interrupt generated as a result of execution in
EL3 is taken locally instead of a lower exception level.

The SError interrupt is enabled in the TSP code only when the operation has not
been directly initiated by the normal world. This is to prevent the possibility
of an asynchronous external abort which originated in normal world from being
taken when execution is in S-EL1.

Fixes ARM-software/tf-issues#153

Change-Id: I157b996c75996d12fd86d27e98bc73dd8bce6cd5

This patch reworks the manner in which the M,A, C, SA, I, WXN & EE bits of
SCTLR_EL3 & SCTLR_EL1 are managed. The EE bit is cleared immediately after reset
in EL3. The I, A and SA bits are set next in EL3 and immediately upon entry in
S-EL1. These bits are no longer managed in the blX_arch_setup() functions. They
do not have to be saved and restored either. The M, WXN and optionally the C
bit are set in the enable_mmu_elX() function. This is done during both the warm
and cold boot paths.

Fixes ARM-software/tf-issues#226

Change-Id: Ie894d1a07b8697c116960d858cd138c50bc7a069

Exclude stdlib files because they do not follow kernel code style.

Fixes ARM-software/tf-issues#73

Change-Id: I4cfafa38ab436f5ab22c277cb38f884346a267ab

Consolidate all BL3-1 CPU context initialization for cold boot, PSCI
and SPDs into two functions:
*  The first uses entry_point_info to initialize the relevant
   cpu_context for first entry into a lower exception level on a CPU
*  The second populates the EL1 and EL2 system registers as needed
   from the cpu_context to ensure correct entry into the lower EL

This patch alters the way that BL3-1 determines which exception level
is used when first entering EL1 or EL2 during cold boot - this is now
fully determined by the SPSR value in the entry_point_info for BL3-3,
as set up by the platform code in BL2 (or otherwise provided to BL3-1).

In the situation that EL1 (or svc mode) is selected for a processor
that supports EL2, the context management code will now configure all
essential EL2 register state to ensure correct execution of EL1. This
allows the platform code to run non-secure EL1 payloads directly
without requiring a small EL2 stub or OS loader.

Change-Id: If9fbb2417e82d2226e47568203d5a369f39d3b0f

The current code does not always use data and instruction
barriers as required by the architecture and frequently uses
barriers excessively due to their inclusion in all of the
write_*() helper functions.

Barriers should be used explicitly in assembler or C code
when modifying processor state that requires the barriers in
order to enable review of correctness of the code.

This patch removes the barriers from the helper functions and
introduces them as necessary elsewhere in the code.

PORTING NOTE: check any port of Trusted Firmware for use of
system register helper functions for reliance on the previous
barrier behaviour and add explicit barriers as necessary.

Fixes ARM-software/tf-issues#92

Change-Id: Ie63e187404ff10e0bdcb39292dd9066cb84c53bf

SCTLR_EL3.EE is being configured too late in bl1_arch_setup() and
bl31_arch_setup() after data accesses have already occured on
the cold and warm boot paths.

This control bit must be configured immediately on CPU reset to
match the endian state of the firmware (little endian).

Fixes ARM-software/tf-issues#145

Change-Id: Ie12e46fbbed6baf024c30beb50751591bb8c8655

Reduce the number of header files included from other header
files as much as possible without splitting the files. Use forward
declarations where possible. This allows removal of some unnecessary
"#ifndef __ASSEMBLY__" statements.

Also, review the .c and .S files for which header files really need
including and reorder the #include statements alphabetically.

Fixes ARM-software/tf-issues#31

Change-Id: Iec92fb976334c77453e010b60bcf56f3be72bd3e

BL3-1 architecture setup code programs the system counter frequency
into the CNTFRQ_EL0 register. This frequency is defined by the
platform, though. This patch introduces a new platform hook that
the architecture setup code can call to retrieve this information.
In the ARM FVP port, this returns the first entry of the frequency
modes table from the memory mapped generic timer.

All system counter setup code has been removed from BL1 as some
platforms may not have initialized the system counters at this stage.
The platform specific settings done exclusively in BL1 have been moved
to BL3-1. In the ARM FVP port, this consists in enabling and
initializing the System level generic timer. Also, the frequency change
request in the counter control register has been set to 0 to make it
explicit it's using the base frequency. The CNTCR_FCREQ() macro has been
fixed in this context to give an entry number rather than a bitmask.

In future, when support for firmware update is implemented, there
is a case where BL1 platform specific code will need to program
the counter frequency. This should be implemented at that time.

This patch also updates the relevant documentation.

It properly fixes ARM-software/tf-issues#24

Change-Id: If95639b279f75d66ac0576c48a6614b5ccb0e84b

This reverts commit 1c297bf0
because it introduced a bug: the CNTFRQ_EL0 register was no
longer programmed by all CPUs.  bl31_platform_setup() function
is invoked only in the cold boot path and consequently only
on the primary cpu.

A subsequent commit will correctly implement the necessary changes
to the counter frequency setup code.

Fixes ARM-software/tf-issues#125

Conflicts:

	docs/firmware-design.md
	plat/fvp/bl31_plat_setup.c

Change-Id: Ib584ad7ed069707ac04cf86717f836136ad3ab54