[U-Boot] [PATCH 3/8 v2] Introduce the Tertiary Program loader

[Haiying.Wang at freescale.com]

From: Haiying Wang <Haiying.Wang at freescale.com>

TPL is introduced to enable a loader stub that boots out of some type of RAM,
after being loaded by an SPL or similar platform-specific mechanism.

One example of using this tpl loader is to initialize the ddr through spd code
in case the L2 SRAM size is not big enough to hold the final uboot image and
the nand spl code needs to be limitated to 4K byte, then tpl code will load the
final uboot image after ddr is initialized.

Signed-off-by: Haiying Wang <Haiying.Wang at freescale.com>
---
Incorporate Mike's comment to use new variable NAND_SPL_OBJS-y
 Makefile |   17 +++++++++++++++--
 README   |   27 +++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 87a383d..94af465 100644
--- a/Makefile
+++ b/Makefile
@@ -290,6 +290,10 @@ LDPPFLAGS += \
 	$(shell $(LD) --version | \
 	  sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')
 
+ifeq ($(CONFIG_TPL_U_BOOT),y)
+TPL_BOOT = tpl
+endif
+
 ifeq ($(CONFIG_NAND_U_BOOT),y)
 NAND_SPL = nand_spl
 U_BOOT_NAND = $(obj)u-boot-nand.bin
@@ -407,8 +411,15 @@ $(obj)u-boot.lds: $(LDSCRIPT)
 $(NAND_SPL):	$(TIMESTAMP_FILE) $(VERSION_FILE) depend
 		$(MAKE) -C nand_spl/board/$(BOARDDIR) all
 
-$(U_BOOT_NAND):	$(NAND_SPL) $(obj)u-boot.bin
-		cat $(obj)nand_spl/u-boot-spl-16k.bin $(obj)u-boot.bin > $(obj)u-boot-nand.bin
+$(TPL_BOOT):	$(TIMESTAMP_FILE) $(VERSION_FILE) depend
+		$(MAKE) -C tpl/board/$(BOARDDIR) all
+
+NAND_SPL_OBJS-y += $(obj)nand_spl/u-boot-spl-16k.bin
+NAND_SPL_OBJS-$(CONFIG_TPL_U_BOOT) += $(obj)tpl/u-boot-tpl.bin
+NAND_SPL_OBJS-y += $(obj)u-boot.bin
+
+$(U_BOOT_NAND): $(NAND_SPL) $(TPL_BOOT) $(obj)u-boot.bin
+		cat $(NAND_SPL_OBJS-y) > u-boot-nand.bin
 
 $(ONENAND_IPL):	$(TIMESTAMP_FILE) $(VERSION_FILE) $(obj)include/autoconf.mk
 		$(MAKE) -C onenand_ipl/board/$(BOARDDIR) all
@@ -1226,6 +1237,7 @@ clean:
 	@rm -f $(obj)lib/asm-offsets.s
 	@rm -f $(obj)nand_spl/{u-boot.lds,u-boot-spl,u-boot-spl.map,System.map}
 	@rm -f $(obj)onenand_ipl/onenand-{ipl,ipl.bin,ipl.map}
+	@rm -f $(obj)tpl/{u-boot-tpl,u-boot-tpl.map}
 	@rm -f $(ONENAND_BIN)
 	@rm -f $(obj)onenand_ipl/u-boot.lds
 	@rm -f $(TIMESTAMP_FILE) $(VERSION_FILE)
@@ -1250,6 +1262,7 @@ clobber:	clean
 	@rm -fr $(obj)include/generated
 	@[ ! -d $(obj)nand_spl ] || find $(obj)nand_spl -name "*" -type l -print | xargs rm -f
 	@[ ! -d $(obj)onenand_ipl ] || find $(obj)onenand_ipl -name "*" -type l -print | xargs rm -f
+	@[ ! -d $(obj)tpl ] || find $(obj)tpl -name "*" -type l -print | xargs rm -f
 
 ifeq ($(OBJTREE),$(SRCTREE))
 mrproper \
diff --git a/README b/README
index 68f5fb0..9c7d40d 100644
--- a/README
+++ b/README
@@ -2108,6 +2108,33 @@ FIT uImage format:
 		Adds the MTD partitioning infrastructure from the Linux
 		kernel. Needed for UBI support.
 
+- NAND Boot Support
+		CONFIG_NAND_U_BOOT
+
+		Builds a U-Boot image that boots from NAND, prefixed by a small
+		loader stub (secondary program loader -- SPL) that loads the
+		rest of U-Boot into RAM.  This symbol will be set in all build
+		phases.
+
+		CONFIG_NAND_SPL
+
+		This is set by the build system when compiling code to go into
+		the SPL.  It is not set when building the code that the SPL
+		loads.
+ 
+- TPL Boot Support
+		CONFIG_TPL_U_BOOT
+
+		Builds a U-Boot image that contains a loader stub (tertiary
+		program loader -- TPL) that boots out of some type of RAM,
+		after being loaded by an SPL or similar platform-specific
+		mechanism.  This symbol will be set in all build phases.
+
+		CONFIG_TPL_BOOT
+
+		This is set by the build system when compiling code to go into
+		the TPL.  It is not set when building the code that the TPL
+		loads, or when building the SPL.
 
 Modem Support:
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1.7.3.1.50.g1e633