u-boot has a standard "serial#" environment variable that is suitable
for storing the iSerial number we will supply via the USB device
descriptor. serial# is automatically picked up by the disk subsystem in
u-boot - thus providing a handy unique identifier in /dev/disk/by-id as
detailed below.

Storing the hardware serial identifier in serial# means we can change the
serial# if we want before USB enumeration - thus making iSerial automatic
via OTP but overridable if necessary.

This patch reads the defined OTP fuse and sets environment variable
"serial#" to the value read.

With this patch in place the USB mass storage device will appear in
/dev/disk/by-id with a unique name based on the OTP value. For example

/dev/disk/by-id/usb-Linux_UMS_disk_0_WaRP7-0xf42400d3000001d4-0:0

Signed-off-by: Bryan O'Donoghue <bryan.odonog...@linaro.org>
Cc: Fabio Estevam <fabio.este...@nxp.com>
Cc: Rui Miguel Silva <rui.si...@linaro.org>
Cc: Ryan Harkin <ryan.har...@linaro.org>
---
 board/warp7/warp7.c     | 14 ++++++++++++++
 include/configs/warp7.h |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/board/warp7/warp7.c b/board/warp7/warp7.c
index d422d63..327f656 100644
--- a/board/warp7/warp7.c
+++ b/board/warp7/warp7.c
@@ -23,6 +23,8 @@
 #include <power/pmic.h>
 #include <power/pfuze3000_pmic.h>
 #include "../freescale/common/pfuze.h"
+#include <asm/setup.h>
+#include <asm/bootm.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -186,6 +188,10 @@ int board_usb_phy_mode(int port)
 int board_late_init(void)
 {
        struct wdog_regs *wdog = (struct wdog_regs *)WDOG1_BASE_ADDR;
+#ifdef CONFIG_SERIAL_TAG
+       struct tag_serialnr serialnr;
+       char serial_string[0x20];
+#endif
 
        imx_iomux_v3_setup_multiple_pads(wdog_pads, ARRAY_SIZE(wdog_pads));
 
@@ -197,5 +203,13 @@ int board_late_init(void)
         */
        clrsetbits_le16(&wdog->wcr, 0, 0x10);
 
+#ifdef CONFIG_SERIAL_TAG
+       /* Set serial# standard environment variable based on OTP settings */
+       get_board_serial(&serialnr);
+       snprintf(serial_string, sizeof(serial_string), "WaRP7-0x%08x%08x",
+                serialnr.low, serialnr.high);
+       env_set("serial#", serial_string);
+#endif
+
        return 0;
 }
diff --git a/include/configs/warp7.h b/include/configs/warp7.h
index fe96988..0c3b605 100644
--- a/include/configs/warp7.h
+++ b/include/configs/warp7.h
@@ -24,6 +24,9 @@
 #define CONFIG_SYS_FSL_ESDHC_HAS_DDR_MODE
 #define CONFIG_SYS_MMC_IMG_LOAD_PART   1
 
+/* Switch on SERIAL_TAG */
+#define CONFIG_SERIAL_TAG
+
 #define CONFIG_DFU_ENV_SETTINGS \
        "dfu_alt_info=boot raw 0x2 0x400 mmcpart 1\0" \
 
-- 
2.7.4

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