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>

docs/user-guide.rst

@@ -664,9 +664,10 @@ ARM development platform specific build options
 
 -  ``ARM_TSP_RAM_LOCATION``: location of the TSP binary. Options:
 
-   -  ``tsram`` : Trusted SRAM (default option)
+   -  ``tsram`` : Trusted SRAM (default option when TBB is not enabled)
    -  ``tdram`` : Trusted DRAM (if available)
-   -  ``dram`` : Secure region in DRAM (configured by the TrustZone controller)
+   -  ``dram``  : Secure region in DRAM (default option when TBB is enabled,
+                  configured by the TrustZone controller)
 
 -  ``ARM_XLAT_TABLES_LIB_V1``: boolean option to compile the Trusted Firmware
    with version 1 of the translation tables library instead of version 2. It is

plat/arm/common/arm_common.mk

@@ -9,7 +9,12 @@ ifeq (${ARCH}, aarch64)
   # DRAM (if available) or the TZC secured area of DRAM.
   # Trusted SRAM is the default.
 
-  ARM_TSP_RAM_LOCATION	:=	tsram
+  ifneq (${TRUSTED_BOARD_BOOT},0)
+    ARM_TSP_RAM_LOCATION	?=	dram
+  else
+    ARM_TSP_RAM_LOCATION	?=	tsram
+  endif
+
   ifeq (${ARM_TSP_RAM_LOCATION}, tsram)
     ARM_TSP_RAM_LOCATION_ID = ARM_TRUSTED_SRAM_ID
   else ifeq (${ARM_TSP_RAM_LOCATION}, tdram)