Commit Graph

594 Commits

Author SHA1 Message Date
Dimitris Papastamos
59902b7c4c AMU: Add plat interface to select which group 1 counters to enable
A new platform macro `PLAT_AMU_GROUP1_COUNTERS_MASK` controls which
group 1 counters should be enabled. The maximum number of group 1
counters supported by AMUv1 is 16 so the mask can be at most 0xffff.
If the platform does not define this mask, no group 1 counters are
enabled.

A related platform macro `PLAT_AMU_GROUP1_NR_COUNTERS` is used by
generic code to allocate an array to save and restore the counters on
CPU suspend.

Change-Id: I6d135badf4846292de931a43bb563077f42bb47b
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
2018-01-11 12:27:27 +00:00
davidcunado-arm
6ef96ab4fd
Merge pull request #1204 from davidcunado-arm/rv/fip_tool
Add padding at the end of the last entry
2018-01-03 23:48:51 +00:00
davidcunado-arm
8618856733
Merge pull request #1206 from davidcunado-arm/dc/update_userguide
Update dependencies for ARM TF
2018-01-03 21:13:43 +00:00
Jett Zhou
4069fb5f39 docs: Update the ToC end marker description in the document
Change-Id: I2e29a63f08aed3b8ea0bb10170a3d55b8d033e62
Signed-off-by: Jett Zhou <jett.zhou@arm.com>
Signed-off-by: David Cunado <david.cunado@arm.com>
2018-01-03 20:51:43 +00:00
davidcunado-arm
9a2a38a201
Merge pull request #1203 from masahir0y/uniphier
uniphier: a bundle of fixes
2017-12-24 19:52:17 +00:00
David Cunado
fa05efb3d5 Update dependencies for ARM TF
ARM TF has been tested as part of its CI system with the following
dependencies updated:

- Linaro binaries:    17.04 --> 17.10
- mbed TLS library:   2.4.2 --> 2.6.0

The version of AEM, Cortex-A and Foundation models that ARM TF is
tested on has also been updated:

- v11.1 build 11.1:22 --> v11.2 build 11.2:33
- v8.9 build 0.8:8805 --> v9.0 build 0.8:9005

This patch updates the user guide documentation to reflect these
changes to the dependencies.

Additionally, links to Linaro resources have been updated.

Change-Id: I9ea5cb76e7443c9dbb0c9525069f450a02f59e58
Signed-off-by: David Cunado <david.cunado@arm.com>
2017-12-21 09:43:49 +00:00
Masahiro Yamada
58b6fccffe doc: uniphier: reformat reStructuredText manually
Commit 6f62574767 ("Convert documentation to reStructuredText")
automatically converted all documents by a tool.  I see some parts
were converted in an ugly way (or, at least, it is not my intention).
Also, the footnote is apparently broken.

I checked this document by my eyes, and reformated it so that it looks
nicer both in plain text and reST form.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-12-20 12:33:01 +09:00
Antonio Nino Diaz
100ac09097 Add Secure Partition Manager (SPM) design document
This patch adds documentation that describes the design of the Secure
Partition Manager and the specific choices in their current
implementation.

The document "SPM User Guide" has been integrated into the design
document.

Change-Id: I0a4f21a2af631c8aa6c739d97a5b634f3cb39991
Co-authored-by: Achin Gupta <achin.gupta@arm.com>
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
2017-12-15 11:47:22 +00:00
davidcunado-arm
211d307c6b
Merge pull request #1178 from davidcunado-arm/dc/enable_sve
Enable SVE for Non-secure world
2017-12-11 12:29:47 +00:00
davidcunado-arm
c1e7ae0adb
Merge pull request #1186 from antonio-nino-diaz-arm/an/poplar-doc
poplar: Fix format of documentation
2017-12-09 15:22:48 +00:00
Antonio Nino Diaz
ded88a009d poplar: Fix format of documentation
The document was being rendered incorrectly.

Change-Id: I6e243d17d7cb6247f91698bc195eb0f6efeb7d17
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
2017-12-06 10:33:15 +00:00
davidcunado-arm
3923bdb019
Merge pull request #1157 from antonio-nino-diaz-arm/an/rpi3
Introduce AArch64 Raspberry Pi 3 port
2017-12-05 23:26:40 +00:00
Antonio Nino Diaz
1cd4fb650e rpi3: Add documentation of Raspberry Pi 3 port
Added design documentation and usage guide for the AArch64 port of the
Arm Trusted Firmware to the Raspberry Pi 3.

Change-Id: I1be60fbbd54c797b48a1bcebfb944d332616a0de
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
2017-12-01 11:11:26 +00:00
David Cunado
1a853370ff Enable SVE for Non-secure world
This patch adds a new build option, ENABLE_SVE_FOR_NS, which when set
to one EL3 will check to see if the Scalable Vector Extension (SVE) is
implemented when entering and exiting the Non-secure world.

If SVE is implemented, EL3 will do the following:

- Entry to Non-secure world: SIMD, FP and SVE functionality is enabled.

- Exit from Non-secure world: SIMD, FP and SVE functionality is
  disabled. As SIMD and FP registers are part of the SVE Z-registers
  then any use of SIMD / FP functionality would corrupt the SVE
  registers.

The build option default is 1. The SVE functionality is only supported
on AArch64 and so the build option is set to zero when the target
archiecture is AArch32.

This build option is not compatible with the CTX_INCLUDE_FPREGS - an
assert will be raised on platforms where SVE is implemented and both
ENABLE_SVE_FOR_NS and CTX_INCLUDE_FPREGS are set to 1.

Also note this change prevents secure world use of FP&SIMD registers on
SVE-enabled platforms. Existing Secure-EL1 Payloads will not work on
such platforms unless ENABLE_SVE_FOR_NS is set to 0.

Additionally, on the first entry into the Non-secure world the SVE
functionality is enabled and the SVE Z-register length is set to the
maximum size allowed by the architecture. This includes the use case
where EL2 is implemented but not used.

Change-Id: Ie2d733ddaba0b9bef1d7c9765503155188fe7dae
Signed-off-by: David Cunado <david.cunado@arm.com>
2017-11-30 17:45:09 +00:00
Soby Mathew
5744e8746d ARM platforms: Fixup AArch32 builds
This patch fixes a couple of issues for AArch32 builds on ARM reference
platforms :

1. The arm_def.h previously defined the same BL32_BASE value for AArch64 and
   AArch32 build. Since BL31 is not present in AArch32 mode, this meant that
   the BL31 memory is empty when built for AArch32. Hence this patch allocates
   BL32 to the memory region occupied by BL31 for AArch32 builds.

   As a side-effect of this change, the ARM_TSP_RAM_LOCATION macro cannot
   be used to control the load address of BL32 in AArch32 mode which was
   never the intention of the macro anyway.

2. A static assert is added to sp_min linker script to check that the progbits
   are within the bounds expected when overlaid with other images.

3. Fix specifying `SPD` when building Juno for AArch32 mode. Due to the quirks
   involved when building Juno for AArch32 mode, the build option SPD needed to
   specifed. This patch corrects this and also updates the documentation in the
   user-guide.

4. Exclude BL31 from the build and FIP when building Juno for AArch32 mode. As
   a result the previous assumption that BL31 must be always present is removed
   and the certificates for BL31 is only generated if `NEED_BL31` is defined.

Change-Id: I1c39bbc0abd2be8fbe9f2dea2e9cb4e3e3e436a8
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
2017-11-29 14:37:29 +00:00
Dimitris Papastamos
380559c1c3 AMU: Implement support for aarch64
The `ENABLE_AMU` build option can be used to enable the
architecturally defined AMU counters.  At present, there is no support
for the auxiliary counter group.

Change-Id: I7ea0c0a00327f463199d1b0a481f01dadb09d312
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
2017-11-29 09:36:05 +00:00
Dimitris Papastamos
0319a97747 Implement support for the Activity Monitor Unit on Cortex A75
The Cortex A75 has 5 AMU counters.  The first three counters are fixed
and the remaining two are programmable.

A new build option is introduced, `ENABLE_AMU`.  When set, the fixed
counters will be enabled for use by lower ELs.  The programmable
counters are currently disabled.

Change-Id: I4bd5208799bb9ed7d2596e8b0bfc87abbbe18740
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
2017-11-29 09:36:05 +00:00
davidcunado-arm
71f8a6a9b0
Merge pull request #1145 from etienne-lms/rfc-armv7-2
Support ARMv7 architectures
2017-11-23 23:41:24 +00:00
davidcunado-arm
e2ff5ef861
Merge pull request #1165 from geesun/qx/support-sha512
Add support sha512 for hash algorithm
2017-11-22 22:42:12 +00:00
davidcunado-arm
a2d60b20ff
Merge pull request #1161 from jeenu-arm/sdei-fixes
SDEI fixes
2017-11-22 13:57:03 +00:00
Qixiang Xu
9a3088a5f5 tbbr: Add build flag HASH_ALG to let the user to select the SHA
The flag support the following values:
    - sha256 (default)
    - sha384
    - sha512

Change-Id: I7a49d858c361e993949cf6ada0a86575c3291066
Signed-off-by: Qixiang Xu <qixiang.xu@arm.com>
2017-11-21 14:16:18 +08:00
Dimitris Papastamos
c776deed60 Change Statistical Profiling Extensions build option handling
It is not possible to detect at compile-time whether support for an
optional extension such as SPE should be enabled based on the
ARM_ARCH_MINOR build option value.  Therefore SPE is now enabled by
default.

Change-Id: I670db164366aa78a7095de70a0962f7c0328ab7c
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
2017-11-20 09:55:01 +00:00
Jeenu Viswambharan
1a0f8f3957 SDEI: Update doc to clarify delegation
The explicit event dispatch sequence currently depicts handling done in
Secure EL1, although further error handling is typically done inside a
Secure Partition. Clarify the sequence diagram to that effect.

Change-Id: I53deedc6d5ee0706626890067950c2c541a62c78
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-11-20 08:15:46 +00:00
David Cunado
91089f360a Move FPEXC32_EL2 to FP Context
The FPEXC32_EL2 register controls SIMD and FP functionality when the
lower ELs are executing in AArch32 mode. It is architecturally mapped
to AArch32 system register FPEXC.

This patch removes FPEXC32_EL2 register from the System Register context
and adds it to the floating-point context. EL3 only saves / restores the
floating-point context if the build option CTX_INCLUDE_FPREGS is set to 1.

The rationale for this change is that if the Secure world is using FP
functionality and EL3 is not managing the FP context, then the Secure
world will save / restore the appropriate FP registers.

NOTE - this is a break in behaviour in the unlikely case that
CTX_INCLUDE_FPREGS is set to 0 and the platform contains an AArch32
Secure Payload that modifies FPEXC, but does not save and restore
this register

Change-Id: Iab80abcbfe302752d52b323b4abcc334b585c184
Signed-off-by: David Cunado <david.cunado@arm.com>
2017-11-15 22:42:05 +00:00
Jeenu Viswambharan
cafad7be04 docs: Add SDEI dispatcher documentation
The document includes SDEI sequence diagrams that are generated using
PlantUML [1].

A shell script is introduced to generate SVG files from PlantUML files
supplied in arguments.

[1] http://plantuml.com/PlantUML_Language_Reference_Guide.pdf

Change-Id: I433897856810bf1927f2800a7b2b1d81827c69b2
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-11-13 08:38:51 +00:00
Jeenu Viswambharan
b7cb133e5c BL31: Add SDEI dispatcher
The implementation currently supports only interrupt-based SDEI events,
and supports all interfaces as defined by SDEI specification version
1.0 [1].

Introduce the build option SDEI_SUPPORT to include SDEI dispatcher in
BL31.

Update user guide and porting guide. SDEI documentation to follow.

[1] http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf

Change-Id: I758b733084e4ea3b27ac77d0259705565842241a
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-11-13 08:38:51 +00:00
Jeenu Viswambharan
21b818c05f BL31: Introduce Exception Handling Framework
EHF is a framework that allows dispatching of EL3 interrupts to their
respective handlers in EL3.

This framework facilitates the firmware-first error handling policy in
which asynchronous exceptions may be routed to EL3. Such exceptions may
be handed over to respective exception handlers. Individual handlers
might further delegate exception handling to lower ELs.

The framework associates the delegated execution to lower ELs with a
priority value. For interrupts, this corresponds to the priorities
programmed in GIC; for other types of exceptions, viz. SErrors or
Synchronous External Aborts, individual dispatchers shall explicitly
associate delegation to a secure priority. In order to prevent lower
priority interrupts from preempting higher priority execution, the
framework provides helpers to control preemption by virtue of
programming Priority Mask register in the interrupt controller.

This commit allows for handling interrupts targeted at EL3. Exception
handlers own interrupts by assigning them a range of secure priorities,
and registering handlers for each priority range it owns.

Support for exception handling in BL31 image is enabled by setting the
build option EL3_EXCEPTION_HANDLING=1.

Documentation to follow.

NOTE: The framework assumes the priority scheme supported by platform
interrupt controller is compliant with that of ARM GIC architecture (v2
or later).

Change-Id: I7224337e4cea47c6ca7d7a4ca22a3716939f7e42
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-11-13 07:49:30 +00:00
Jeenu Viswambharan
4ee8d0becd GIC: Introduce API to get interrupt ID
Acknowledging interrupt shall return a raw value from the interrupt
controller in which the actual interrupt ID may be encoded. Add a
platform API to extract the actual interrupt ID from the raw value
obtained from interrupt controller.

Document the new function. Also clarify the semantics of interrupt
acknowledge.

Change-Id: I818dad7be47661658b16f9807877d259eb127405
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-11-13 07:49:30 +00:00
Antonio Nino Diaz
e29efeb1b4 SPM: FVP: Introduce port of SPM
This initial port of the Secure Partitions Manager to FVP supports BL31
in both SRAM and Trusted DRAM.

A document with instructions to build the SPM has been added.

Change-Id: I4ea83ff0a659be77f2cd72eaf2302cdf8ba98b32
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Co-authored-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Co-authored-by: Achin Gupta <achin.gupta@arm.com>
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
2017-11-09 11:34:09 +00:00
Etienne Carriere
26e63c4450 ARMv7 target is driven by ARM_ARCH_MAJOR==7
External build environment shall sets directive ARM_ARCH_MAJOR to 7
to specify a target ARMv7-A core.

As ARM-TF expects AARCH to be set, ARM_ARCH_MAJOR==7 mandates
AARCH=aarch32.

The toolchain target architecture/cpu is delegated after the platform
configuration is parsed. Platform shall define target core through
ARM_CORTEX_A<x>=yes, <x> being 5, 7, 9, 12, 15 and/or 17.

Platform can bypass ARM_CORTEX_A<x>=yes directive and provide straight
the toolchain target directive through MARCH32_DIRECTIVE.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
2017-11-08 13:48:40 +01:00
davidcunado-arm
122af7dd6d
Merge pull request #1150 from dp-arm/dp/events
aarch64: Add PubSub events to capture security state transitions
2017-11-01 08:46:02 +00:00
davidcunado-arm
5b5e6cb742
Merge pull request #1149 from robertovargas-arm/fwu-testing
Add FWU booting instructions to the user guide
2017-10-31 23:23:56 +00:00
davidcunado-arm
27b2493c6f
Merge pull request #1141 from robertovargas-arm/boot_redundancy
Add platform hooks for boot redundancy support
2017-10-31 23:21:39 +00:00
Dimitris Papastamos
17b4c0dd0a aarch64: Add PubSub events to capture security state transitions
Add events that trigger before entry to normal/secure world.  The
events trigger after the normal/secure context has been restored.

Similarly add events that trigger after leaving normal/secure world.
The events trigger after the normal/secure context has been saved.

Change-Id: I1b48a7ea005d56b1f25e2b5313d77e67d2f02bc5
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
2017-10-31 10:33:27 +00:00
Roberto Vargas
e29ee4693d Add FWU booting instructions to the user guide
FWU uses additional images that have to be loaded,
and this patch adds the documentation of how to do
it in FVP and Juno.

Change-Id: I1a40641c11c5a4c8db0aadeaeb2bec30c9279e28
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
2017-10-31 08:54:44 +00:00
Qixiang Xu
7ca267bd8a plat/arm: change the default option of ARM_TSP_RAM_LOCATION
On Arm standard platforms, it runs out of SRAM space when TBB is
enabled, so the TSP default location is changed to dram when TBB
is enabled.

Change-Id: I516687013ad436ef454d2055d4e6fce06e467044
Signed-off-by: Qixiang Xu <qixiang.xu@arm.com>
2017-10-25 09:27:15 +08:00
Roberto Vargas
01f62b6d0d Add platform hooks for boot redundancy support
These hooks are intended to allow one platform to try load
images from alternative places. There is a hook to initialize
the sequence of boot locations and a hook to pass to the next
sequence.

Change-Id: Ia0f84c415208dc4fa4f9d060d58476db23efa5b2
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
2017-10-24 14:04:41 +01:00
Jeenu Viswambharan
bd0c347781 PSCI: Publish CPU ON event
This allows other EL3 components to subscribe to CPU on events.

Update Firmware Design guide to list psci_cpu_on_finish as an available
event.

Change-Id: Ida774afe0f9cdce4021933fcc33a9527ba7aaae2
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-23 08:15:11 +01:00
Jeenu Viswambharan
8e743bcd6a BL31: Introduce Publish and Subscribe framework
This light-weight framework enables some EL3 components to publish
events which other EL3 components can subscribe to. Publisher can
optionally pass opaque data for subscribers. The order in which
subscribers are called is not defined.

Firmware design updated.

Change-Id: I24a3a70b2b1dedcb1f73cf48313818aebf75ebb6
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-23 08:15:11 +01:00
davidcunado-arm
623c43774a Merge pull request #1130 from jeenu-arm/gic-patches
New GIC APIs and specifying interrupt propertes
2017-10-21 22:18:48 +01:00
davidcunado-arm
3daf7c9aae Merge pull request #1140 from eleanorbonnici-arm/eb/docs/update_models
Update Foundation, AEM and Cortex Models versions
2017-10-18 23:39:30 +01:00
Eleanor Bonnici
99f38f513d Update Foundation, AEM and Cortex Models versions
Trusted Firmware has been tested as part of its CI system against Cortex
and Foundation models in the 11.1 Model release available on
developer.arm.com. Trusted Firmware has also been tested against the
v8.7 AEM model.  This patch updates the user guide documentation to
reflect the version of the Foundation, AEM and Cortex Models that
Trusted Firmware has been tested against.

Change-Id: Ia0f51469032427b6056567d151bf8144a7cf0e42
Signed-off-by: Eleanor Bonnici <Eleanor.bonnici@arm.com>
2017-10-18 14:29:45 +01:00
davidcunado-arm
38f5d3f340 Merge pull request #1133 from geesun/qx/fixed_tbbr_doc_ver
docs: Update Trusted Board Boot Requirements document number
2017-10-17 17:29:42 +01:00
davidcunado-arm
5d2f87e850 Merge pull request #1126 from robertovargas-arm/psci-v1.1
Update PSCI to v1.1
2017-10-17 12:18:23 +01:00
Jeenu Viswambharan
c639e8ebee GIC: Allow specifying interrupt properties
The GIC driver initialization currently allows an array of interrupts to
be configured as secure. Future use cases would require more interrupt
configuration other than just security, such as priority.

This patch introduces a new interrupt property array as part of both
GICv2 and GICv3 driver data. The platform can populate the array with
interrupt numbers and respective properties. The corresponding driver
initialization iterates through the array, and applies interrupt
configuration as required.

This capability, and the current way of supplying array (or arrays, in
case of GICv3) of secure interrupts, are however mutually exclusive.
Henceforth, the platform should supply either:

  - A list of interrupts to be mapped as secure (the current way).
    Platforms that do this will continue working as they were. With this
    patch, this scheme is deprecated.

  - A list of interrupt properties (properties include interrupt group).
    Individual interrupt properties are specified via. descriptors of
    type 'interrupt_prop_desc_t', which can be populated with the macro
    INTR_PROP_DESC().

A run time assert checks that the platform doesn't specify both.

Henceforth the old scheme of providing list of secure interrupts is
deprecated. When built with ERROR_DEPRECATED=1, GIC drivers will require
that the interrupt properties are supplied instead of an array of secure
interrupts.

Add a section to firmware design about configuring secure interrupts.

Fixes ARM-software/tf-issues#262

Change-Id: I8eec29e72eb69dbb6bce77879febf32c95376942
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-16 16:50:02 +01:00
Jeenu Viswambharan
d55a445069 GIC: Add API to set priority mask
API documentation updated.

Change-Id: I40feec1fe67a960d035061b54dd55610bc34ce1d
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-16 16:50:02 +01:00
Jeenu Viswambharan
a2816a1644 GIC: Add API to set/clear interrupt pending
API documentation updated.

Change-Id: I14e33cfc7dfa93257c82d76fae186b17a1b6d266
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-16 16:50:02 +01:00
Jeenu Viswambharan
fc529fee72 GIC: Add API to set interrupt routing
SPIs can be routed to either a specific PE, or to any one of all
available PEs.

API documentation updated.

Change-Id: I28675f634568aaf4ea1aa8aa7ebf25b419a963ed
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-16 16:50:02 +01:00
Jeenu Viswambharan
8db978b5a8 GIC: Add API to raise secure SGI
API documentation updated.

Change-Id: I129725059299af6cc612bafa8d74817f779d7c4f
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-16 16:50:02 +01:00
Jeenu Viswambharan
74dce7fa6e GIC: Add APIs to set interrupt type and query support
The back end GIC driver converts and assigns the interrupt type to
suitable group.

For GICv2, a build option GICV2_G0_FOR_EL3 is introduced, which
determines to which type Group 0 interrupts maps to.

 - When the build option is set 0 (the default), Group 0 interrupts are
   meant for Secure EL1. This is presently the case.

 - Otherwise, Group 0 interrupts are meant for EL3. This means the SPD
   will have to synchronously hand over the interrupt to Secure EL1.

The query API allows the platform to query whether the platform supports
interrupts of a given type.

API documentation updated.

Change-Id: I60fdb4053ffe0bd006b3b20914914ebd311fc858
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
2017-10-16 16:50:01 +01:00