[PATCH v3 09/13] binman: Support packaging U-Boot for scenarios like OF_BOARD or OF_PRIOR_STAGE

[Bin Meng]

For scenarios like OF_BOARD or OF_PRIOR_STAGE, no device tree blob is
provided in the U-Boot build phase hence the binman node information
is not available. In order to support such use case, a new Kconfig
option BINMAN_STANDALONE_FDT is introduced, to tell the build system
that a device tree blob containing binman node is explicitly required
when using binman to package U-Boot.

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>

---

Changes in v3:
- rename the Kconfig option name to BINMAN_STANDALONE_FDT
- make BINMAN_STANDALONE_FDT default y for OF_BOARD as well
- reword the Kconfig option help message a little bit
- update binman.rst to mention OF_BOARD or OF_PRIOR_STAGE usage

Changes in v2:
- new patch: "binman: Support packaging U-Boot for scenarios like OF_PRIOR_STAGE"

 Makefile                |  4 +++-
 dts/Kconfig             | 18 ++++++++++++++++++
 tools/binman/binman.rst | 22 ++++++++++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 3d88559b67..dea06907c0 100644
--- a/Makefile
+++ b/Makefile
@@ -918,6 +918,7 @@ endif
 endif
 INPUTS-$(CONFIG_TPL) += tpl/u-boot-tpl.bin
 INPUTS-$(CONFIG_OF_SEPARATE) += u-boot.dtb
+INPUTS-$(CONFIG_BINMAN_STANDALONE_FDT) += u-boot.dtb
 ifeq ($(CONFIG_SPL_FRAMEWORK),y)
 INPUTS-$(CONFIG_OF_SEPARATE) += u-boot-dtb.img
 endif
@@ -1161,7 +1162,8 @@ u-boot-dtb.bin: u-boot-nodtb.bin dts/dt.dtb FORCE
 u-boot.bin: u-boot-dtb.bin FORCE
 	$(call if_changed,copy)
 else
-u-boot.bin: u-boot-nodtb.bin FORCE
+# if CONFIG_BINMAN_STANDALONE_FDT is turned on, dependency on dts/dt.dtb is required
+u-boot.bin: u-boot-nodtb.bin $(if $(CONFIG_BINMAN_STANDALONE_FDT),dts/dt.dtb) FORCE
 	$(call if_changed,copy)
 endif
 
diff --git a/dts/Kconfig b/dts/Kconfig
index 99ce75e1a2..dabe0080c1 100644
--- a/dts/Kconfig
+++ b/dts/Kconfig
@@ -19,6 +19,24 @@ config BINMAN
 	bool
 	select DTOC
 
+config BINMAN_STANDALONE_FDT
+	bool
+	depends on BINMAN
+	default y if OF_BOARD || OF_PRIOR_STAGE
+	help
+	  This option tells U-Boot build system that a standalone device tree
+	  source is explicitly required when using binman to package U-Boot.
+
+	  This is not necessary in a common scenario where a device tree source
+	  that contains the binman node is provided in the arch/<arch>/dts
+	  directory for a specific board. Such device tree sources are built for
+	  OF_SEPARATE or OF_EMBED. However for a scenario like the board device
+	  tree blob is not provided in the U-Boot build tree, but fed to U-Boot
+	  in the runtime, e.g.: in the OF_PRIOR_STAGE case that it is passed by
+	  a prior stage bootloader. For such scenario, a standalone device tree
+	  blob containing binman node to describe how to package U-Boot should
+	  be provided explicitly.
+
 menu "Device Tree Control"
 	depends on SUPPORT_OF_CONTROL
 
diff --git a/tools/binman/binman.rst b/tools/binman/binman.rst
index b3df3a6428..b158fd34d7 100644
--- a/tools/binman/binman.rst
+++ b/tools/binman/binman.rst
@@ -231,6 +231,28 @@ file, typically <soc>-u-boot.dtsi, where <soc> is your CONFIG_SYS_SOC value.
 You can use other, more specific CONFIG options - see 'Automatic .dtsi
 inclusion' below.
 
+Using binman with OF_BOARD or OF_PRIOR_STAGE
+--------------------------------------------
+
+Normally binman is used with a board configured with OF_SEPARATE or OF_EMBED.
+This is a typical scenario where a device tree source that contains the binman
+node is provided in the arch/<arch>/dts directory for a specific board.
+
+However for a board configured with OF_BOARD or OF_PRIOR_STAGE, no device tree
+blob is provided in the U-Boot build phase hence the binman node information
+is not available. In order to support such use case, a new Kconfig option
+BINMAN_STANDALONE_FDT is introduced, to tell the build system that a standalone
+device tree blob containing binman node is explicitly required.
+
+Note there is a Kconfig option BINMAN_FDT which enables U-Boot run time to
+access information about binman entries, stored in the device tree in a binman
+node. Generally speaking, this option makes sense for OF_SEPARATE or OF_EMBED.
+For the other OF_CONTROL methods, it's quite possible binman node is not
+available as binman is invoked during the build phase, thus this option is not
+turned on by default for these OF_CONTROL methods.
+
+See qemu-riscv64_spl_defconfig for an exmaple of how binman is used with
+OF_PRIOR_STAGE to generate u-boot.itb image.
 
 Access to binman entry offsets at run time (symbols)
 ----------------------------------------------------
-- 
2.25.1