Docs: Update user guide for Dynamic Config on FVP

From TF-A v1.5, FVP supports loading the kernel FDT through
firmware as part of dynamic configuration feature. This means
that the FDT no longer needs to be loaded via Model parameters.
This patch updates the user guide to reflect the same.

Change-Id: I79833beeaae44a1564f6512c3a473625e5959f65
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

docs/user-guide.rst

@@ -1204,6 +1204,10 @@ match the uboot image packaged as BL33 in the corresponding fip file. It is
 recommended to use the version that is packaged in the fip file using the
 instructions below.
 
+Note: For the FVP, the kernel FDT is packaged in FIP during build and loaded
+by the firmware at runtime. See `Obtaining the Flattened Device Trees`_
+section for more info on selecting the right FDT to use.
+
 #. Clean the working directory
 
    ::
@@ -1662,52 +1666,59 @@ Obtaining the Flattened Device Trees
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Depending on the FVP configuration and Linux configuration used, different
-FDT files are required. FDTs for the Foundation and Base FVPs can be found in
-the TF-A source directory under ``fdts/``. The Foundation FVP has a subset of
-the Base FVP components. For example, the Foundation FVP lacks CLCD and MMC
-support, and has only one CPU cluster.
+FDT files are required. FDT source files for the Foundation and Base FVPs can
+be found in the TF-A source directory under ``fdts/``. The Foundation FVP has
+a subset of the Base FVP components. For example, the Foundation FVP lacks
+CLCD and MMC support, and has only one CPU cluster.
 
 Note: It is not recommended to use the FDTs built along the kernel because not
 all FDTs are available from there.
 
--  ``fvp-base-gicv2-psci.dtb``
+The dynamic configuration capability is enabled in the firmware for FVPs.
+This means that the firmware can authenticate and load the FDT if present in
+FIP. A default FDT is packaged into FIP during the build based on
+the build configuration. This can be overridden by using the ``FVP_HW_CONFIG``
+or ``FVP_HW_CONFIG_DTS`` build options (refer to the
+`Arm FVP platform specific build options`_ section for detail on the options).
+
+-  ``fvp-base-gicv2-psci.dts``
 
    For use with models such as the Cortex-A57-A53 Base FVPs without shifted
    affinities and with Base memory map configuration.
 
--  ``fvp-base-gicv2-psci-aarch32.dtb``
+-  ``fvp-base-gicv2-psci-aarch32.dts``
 
    For use with models such as the Cortex-A32 Base FVPs without shifted
    affinities and running Linux in AArch32 state with Base memory map
    configuration.
 
--  ``fvp-base-gicv3-psci.dtb``
+-  ``fvp-base-gicv3-psci.dts``
 
    For use with models such as the Cortex-A57-A53 Base FVPs without shifted
    affinities and with Base memory map configuration and Linux GICv3 support.
 
--  ``fvp-base-gicv3-psci-1t.dtb``
+-  ``fvp-base-gicv3-psci-1t.dts``
 
    For use with models such as the AEMv8-RevC Base FVP with shifted affinities,
    single threaded CPUs, Base memory map configuration and Linux GICv3 support.
 
--  ``fvp-base-gicv3-psci-dynamiq.dtb``
+-  ``fvp-base-gicv3-psci-dynamiq.dts``
 
    For use with models as the Cortex-A55-A75 Base FVPs with shifted affinities,
    single cluster, single threaded CPUs, Base memory map configuration and Linux
    GICv3 support.
 
--  ``fvp-base-gicv3-psci-aarch32.dtb``
+-  ``fvp-base-gicv3-psci-aarch32.dts``
 
    For use with models such as the Cortex-A32 Base FVPs without shifted
    affinities and running Linux in AArch32 state with Base memory map
    configuration and Linux GICv3 support.
 
--  ``fvp-foundation-gicv2-psci.dtb``
+-  ``fvp-foundation-gicv2-psci.dts``
 
    For use with Foundation FVP with Base memory map configuration.
 
--  ``fvp-foundation-gicv3-psci.dtb``
+-  ``fvp-foundation-gicv3-psci.dts``
 
    (Default) For use with Foundation FVP with Base memory map configuration
    and Linux GICv3 support.
@@ -1728,7 +1739,6 @@ The following ``Foundation_Platform`` parameters should be used to boot Linux wi
     --gicv3                                         \
     --data="<path-to>/<bl1-binary>"@0x0             \
     --data="<path-to>/<FIP-binary>"@0x08000000      \
-    --data="<path-to>/<fdt>"@0x82000000             \
     --data="<path-to>/<kernel-binary>"@0x80080000   \
     --data="<path-to>/<ramdisk-binary>"@0x84000000
 
@@ -1736,7 +1746,8 @@ Notes:
 
 -  BL1 is loaded at the start of the Trusted ROM.
 -  The Firmware Image Package is loaded at the start of NOR FLASH0.
--  The Linux kernel image and device tree are loaded in DRAM.
+-  The firmware loads the FDT packaged in FIP to the DRAM. The FDT load address
+   is specified via the ``hw_config_addr`` property in `TB_FW_CONFIG for FVP`_.
 -  The default use-case for the Foundation FVP is to use the ``--gicv3`` option
    and enable the GICv3 device in the model. Note that without this option,
    the Foundation FVP defaults to legacy (Versatile Express) memory map which
@@ -1765,7 +1776,6 @@ with 8 CPUs using the AArch64 build of TF-A.
     -C cache_state_modelled=1                                   \
     -C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
     -C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
-    --data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
     --data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
     --data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000
 
@@ -1794,7 +1804,6 @@ with 8 CPUs using the AArch32 build of TF-A.
     -C cluster1.cpu3.CONFIG64=0                                 \
     -C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
     -C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
-    --data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
     --data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
     --data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000
 
@@ -1813,7 +1822,6 @@ boot Linux with 8 CPUs using the AArch64 build of TF-A.
     -C cache_state_modelled=1                                   \
     -C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
     -C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
-    --data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
     --data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
     --data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000
 
@@ -1832,7 +1840,6 @@ boot Linux with 4 CPUs using the AArch32 build of TF-A.
     -C cache_state_modelled=1                                   \
     -C bp.secureflashloader.fname="<path-to>/<bl1-binary>"      \
     -C bp.flashloader0.fname="<path-to>/<FIP-binary>"           \
-    --data cluster0.cpu0="<path-to>/<fdt>"@0x82000000           \
     --data cluster0.cpu0="<path-to>/<kernel-binary>"@0x80080000 \
     --data cluster0.cpu0="<path-to>/<ramdisk>"@0x84000000
 
@@ -1872,7 +1879,9 @@ Notes:
    ``--data="<path-to><bl31|bl32|bl33-binary>"@<base-address-of-binary>``
    parameter is needed to load the individual bootloader images in memory.
    BL32 image is only needed if BL31 has been built to expect a Secure-EL1
-   Payload.
+   Payload. For the same reason, the FDT needs to be compiled from the DT source
+   and loaded via the ``--data cluster0.cpu0="<path-to>/<fdt>"@0x82000000``
+   parameter.
 
 -  The ``-C cluster<X>.cpu<Y>.RVBAR=@<base-address-of-bl31>`` parameter, where
    X and Y are the cluster and CPU numbers respectively, is used to set the
@@ -2030,6 +2039,7 @@ wakeup interrupt from RTC.
 .. _Dia: https://wiki.gnome.org/Apps/Dia/Download
 .. _here: psci-lib-integration-guide.rst
 .. _Trusted Board Boot: trusted-board-boot.rst
+.. _TB_FW_CONFIG for FVP: ../plat/arm/board/fvp/fdts/fvp_tb_fw_config.dts
 .. _Secure-EL1 Payloads and Dispatchers: firmware-design.rst#user-content-secure-el1-payloads-and-dispatchers
 .. _Firmware Update: firmware-update.rst
 .. _Firmware Design: firmware-design.rst