uboot: support -r option for mkenvimage

Some boards are configured in u-boot to store multiple redundant copies of
the environment image in flash.  For these boards, it is required to pass
the -r flag, when generating a boot environment image using mkenvimage.

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/uboot/Config.in

@@ -251,6 +251,20 @@ config BR2_TARGET_UBOOT_ENVIMAGE_SIZE
 	  Size of envronment, can be prefixed with 0x for hexadecimal
 	  values.
 
+config BR2_TARGET_UBOOT_ENVIMAGE_REDUNDANT
+	bool "Environment has two copies"
+	help
+	  Some platforms define in their U-Boot configuration that the
+	  U-Boot environment should be duplicated in two locations (for
+	  extra safety). Check your U-Boot configuration for the
+	  CONFIG_ENV_ADDR_REDUND and CONFIG_ENV_SIZE_REDUND settings to
+	  see if this is the case for your platform.
+
+	  If it is the case, then you should enable this option to
+	  ensure that the U-Boot environment image generated by
+	  Buildroot is compatible with the "redundant environment"
+	  mechanism of U-Boot.
+
 endif # BR2_TARGET_UBOOT_ENVIMAGE
 
 endif # BR2_TARGET_UBOOT

boot/uboot/uboot.mk

@@ -120,6 +120,7 @@ define UBOOT_INSTALL_IMAGES_CMDS
 		cp -dpf $(@D)/$(BR2_TARGET_UBOOT_SPL_NAME) $(BINARIES_DIR)/)
 	$(if $(BR2_TARGET_UBOOT_ENVIMAGE),
 		$(HOST_DIR)/usr/bin/mkenvimage -s $(BR2_TARGET_UBOOT_ENVIMAGE_SIZE) \
+		$(if $(BR2_TARGET_UBOOT_ENVIMAGE_REDUNDANT),-r) \
 		-o $(BINARIES_DIR)/uboot-env.bin $(BR2_TARGET_UBOOT_ENVIMAGE_SOURCE))
 endef