[U-Boot] [PATCH 3/7] spl: nand: support redundant u-boot image

[Boris Brezillon]

On modern NAND it's more than recommended to have a backup copy of the
u-boot binary to recover from corruption: bitflips are quite common on
MLC NANDs, and the read-disturbance will corrupt your u-boot partitition
more quickly than what you would see on an SLC NAND.

Add an extra Kconfig option to specify the offset of the redundant u-boot
image.

Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 common/spl/spl_nand.c    | 8 ++++++++
 drivers/mtd/nand/Kconfig | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/common/spl/spl_nand.c b/common/spl/spl_nand.c
index 612bd4a..0bf0848 100644
--- a/common/spl/spl_nand.c
+++ b/common/spl/spl_nand.c
@@ -12,6 +12,9 @@
 
 #ifndef CONFIG_SYS_NAND_U_BOOT_OFFS
 #define CONFIG_SYS_NAND_U_BOOT_OFFS CONFIG_SPL_NAND_U_BOOT_OFFS
+#define CONFIG_SYS_NAND_U_BOOT_OFFS_REDUND CONFIG_SPL_NAND_U_BOOT_OFFS_REDUND
+#else
+#define CONFIG_SYS_NAND_U_BOOT_OFFS_REDUND CONFIG_SYS_NAND_U_BOOT_OFFS
 #endif
 
 #if defined(CONFIG_SPL_NAND_RAW_ONLY)
@@ -111,6 +114,11 @@ int spl_nand_load_image(void)
 #endif
 	/* Load u-boot */
 	err = spl_nand_load_element(CONFIG_SYS_NAND_U_BOOT_OFFS, header);
+#if CONFIG_SYS_NAND_U_BOOT_OFFS != CONFIG_SYS_NAND_U_BOOT_OFFS_REDUND
+	if (err)
+		err = spl_nand_load_element(CONFIG_SYS_NAND_U_BOOT_OFFS_REDUND,
+					    header);
+#endif
 	nand_deselect();
 	return err;
 }
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index 4b0f92c..2f1d1f7 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -110,6 +110,12 @@ config SPL_NAND_U_BOOT_OFFS
 	Set the offset from the start of the nand where u-boot should be
 	loaded from.
 
+config SPL_NAND_U_BOOT_OFFS_REDUND
+	hex "Location in NAND to read U-Boot from"
+	default SPL_NAND_U_BOOT_OFFS
+	help
+	Set the offset from the start of the nand where u-boot should be
+	loaded from.
 
 config SPL_NAND_DENALI
 	bool "Support Denali NAND controller for SPL"
-- 
2.7.4