boot/uboot: add support for i.MX28 SD format

Allow to generate u-boot.sd, Freescale i.MX28 SB format with a header for
booting from an SD card.

U-boot includes an mxsboot tool to generate this format, starting from
v2011.12.

See u-boot doc/README.mxs (or doc/README.mx28_common before 2013.07).

[Arnout:
 - Wrap Config.in help text at 72 columns.
 - Remove v from U-Boot version specifier.
 - Refer to different README name before 2013.07.
 - Depend on host-elftosb
 - Add comment to clarify sb -> sd conversion.]

Signed-off-by: Vincent Stehlé <vincent.stehle@freescale.com>
Tested-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

boot/uboot/Config.in

@@ -117,6 +117,18 @@ config BR2_TARGET_UBOOT_FORMAT_SB
 	depends on BR2_arm
 	bool "u-boot.sb"
 
+config BR2_TARGET_UBOOT_FORMAT_SD
+	depends on BR2_arm
+	bool "u-boot.sd"
+	help
+	  This is Freescale i.MX28 SB format, with a header for booting
+	  from an SD card.
+
+	  U-boot includes an mxsboot tool to generate this format,
+	  starting from 2011.12.
+
+	  See doc/README.mxs (or doc/README.mx28_common before 2013.07)
+
 config BR2_TARGET_UBOOT_FORMAT_CUSTOM
 	bool "Custom (specify below)"
 	help

boot/uboot/uboot.mk

@@ -49,6 +49,11 @@ else ifeq ($(BR2_TARGET_UBOOT_FORMAT_SB),y)
 UBOOT_BIN = u-boot.sb
 UBOOT_MAKE_TARGET = $(UBOOT_BIN)
 UBOOT_DEPENDENCIES += host-elftosb
+else ifeq ($(BR2_TARGET_UBOOT_FORMAT_SD),y)
+# BootStream (.sb) is generated by U-Boot, we convert it to SD format
+UBOOT_BIN = u-boot.sd
+UBOOT_MAKE_TARGET = u-boot.sb
+UBOOT_DEPENDENCIES += host-elftosb
 else ifeq ($(BR2_TARGET_UBOOT_FORMAT_CUSTOM),y)
 UBOOT_BIN = $(call qstrip,$(BR2_TARGET_UBOOT_FORMAT_CUSTOM_NAME))
 else
@@ -116,6 +121,8 @@ define UBOOT_BUILD_CMDS
 	$(TARGET_CONFIGURE_OPTS) 	\
 		$(MAKE) -C $(@D) $(UBOOT_MAKE_OPTS) 		\
 		$(UBOOT_MAKE_TARGET)
+	$(if $(BR2_TARGET_UBOOT_FORMAT_SD),
+		$(@D)/tools/mxsboot sd $(@D)/u-boot.sb $(@D)/u-boot.sd)
 endef
 
 define UBOOT_BUILD_OMAP_IFT