feat(zynqmp): make stack size configurable

If PLATFORM_STACK_SIZE not already defined, use the default value of
PLATFORM_STACK_SIZE.
This makes the stack size value configurable for different interface
like custom packages.

Signed-off-by: Amit Nagal <amit.nagal@amd.com>
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
Change-Id: I87e9fcbfb4c4092378b1ac0ff8fb6d084495d320

docs/plat/xilinx-zynqmp.rst

@@ -89,6 +89,16 @@ the build command example is;
 make CROSS_COMPILE=aarch64-none-elf- PLAT=zynqmp RESET_TO_BL31=1 DEBUG=1 \
 	ZYNQMP_ATF_MEM_BASE=0x40000 ZYNQMP_ATF_MEM_SIZE=<size>
 
+Configurable Stack Size
+-----------------------
+
+The stack size in TF-A for ZynqMP platform is configurable.
+The custom package can define the desired stack size as per the requirement in
+the make file as follows,
+
+PLATFORM_STACK_SIZE := <value>
+$(eval $(call add_define,PLATFORM_STACK_SIZE))
+
 FSBL->TF-A Parameter Passing
 ----------------------------
 

plat/xilinx/zynqmp/include/platform_def.h

@@ -21,7 +21,9 @@
  ******************************************************************************/
 
 /* Size of cacheable stacks */
+#ifndef PLATFORM_STACK_SIZE
 #define PLATFORM_STACK_SIZE 0x440
+#endif
 
 #define PLATFORM_CORE_COUNT		U(4)
 #define PLAT_NUM_POWER_DOMAINS		U(5)