feat(arm): add initrd props to dtb at build time

Add initrd properties to the device tree blob at build time, giving
users the ability to run a linux kernel and successfully boot it to
the terminal. Users can boot a linux kernel in a normal flow as well
as in RESET_TO_BL31. This function is an extension of the build time
option "ARM_LINUX_KERNEL_AS_BL33=1".

The build time options INITRD_SIZE or INITRD_PATH will trigger the
insertion of initrd properties in to the DTB. If both options are
provided then the INITRD_SIZE will take precedence.

The available options are:
INITRD_SIZE: Provide the initrd size in dec or hex (hex format must
precede with '0x'.
Example: INITRD_SIZE=0x1000000

INITRD_PATH: Provide an initrd path for the build time to find its
exact size.

INITRD_BASE: A required build time option that sets the initrd base
address in hex format. A default value can be set by the platform.
Example: INITRD_BASE=0x90000000

Change-Id: Ief8de5f00c453509bcc6e978e0a95d768f1f509c
Signed-off-by: Salman Nabi <salman.nabi@arm.com>

Makefile

@@ -1638,6 +1638,21 @@ endif #(NEED_BL2U)
 # Expand build macros for the different images
 ifeq (${NEED_FDT},yes)
     $(eval $(call MAKE_DTBS,$(BUILD_PLAT)/fdts,$(FDT_SOURCES)))
+
+    ifneq (${INITRD_SIZE}${INITRD_PATH},)
+        ifndef INITRD_BASE
+            $(error INITRD_BASE must be set when inserting initrd properties to the DTB.)
+        endif
+
+        INITRD_SIZE ?= $(shell printf "0x%x\n" $$(stat -Lc %s $(INITRD_PATH)))
+        initrd_end = $(shell printf "0x%x\n" $$(expr $$(($(INITRD_BASE) + $(INITRD_SIZE)))))
+
+        define $(HW_CONFIG)-after +=
+            $(s)echo "  INITRD  $(HW_CONFIG)"
+            $(q)fdtput -t x $@ /chosen linux,initrd-start $(INITRD_BASE)
+            $(q)fdtput -t x $@ /chosen linux,initrd-end $(initrd_end)
+        endef
+    endif
 endif #(NEED_FDT)
 
 # Add Secure Partition packages

make_helpers/build_macros.mk

@@ -604,6 +604,7 @@ $(DPRE): $(2) | $$$$(@D)/
 $(DOBJ): $(DPRE) $(filter-out %.d,$(MAKEFILE_LIST)) | $$$$(@D)/
 	$$(s)echo "  DTC     $$<"
 	$$(q)$($(ARCH)-dtc) $$(DTC_FLAGS) -d $(DTBDEP) -o $$@ $$<
+	$$($$@-after)
 
 -include $(DTBDEP)
 -include $(DTSDEP)

plat/arm/board/fvp/platform.mk

@@ -367,6 +367,10 @@ FVP_HW_CONFIG_DTS	:=	fdts/${FVP_DT_PREFIX}.dts
 
 FDT_SOURCES		+=	${FVP_HW_CONFIG_DTS}
 $(eval FVP_HW_CONFIG	:=	${BUILD_PLAT}/$(patsubst %.dts,%.dtb,$(FVP_HW_CONFIG_DTS)))
+HW_CONFIG		:=	${FVP_HW_CONFIG}
+
+# Set default initrd base 128MiB offset of the default kernel address in FVP
+INITRD_BASE		?=	0x90000000
 
 ifeq (${TRANSFER_LIST}, 0)
 FDT_SOURCES		+=	$(addprefix plat/arm/board/fvp/fdts/,	\
@@ -419,7 +423,6 @@ ifeq (${TRANSFER_LIST}, 1)
 include lib/transfer_list/transfer_list.mk
 
 ifeq ($(RESET_TO_BL31), 1)
-HW_CONFIG			:=	${FVP_HW_CONFIG}
 FW_HANDOFF_SIZE			:=	20000
 
 TRANSFER_LIST_DTB_OFFSET	:=	0x20