mx6sabre: Use PARTUUID to specify the rootfs location

mx6sabre boards can run different kernel versions, such as NXP 4.1 or
mainline.

Currently the rootfs location is passed via mmcblk number and the
problem with this approach is that the mmcblk number for the eMMC
changes depending on the kernel version.

In order to avoid such issue, use UUID method to specify the rootfs
location.

Succesfully tested booting a NXP 4.1 and also a mainline kernel on a
mx6qsabresd and mx6dlsabreauto.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>

configs/mx6sabreauto_defconfig

@@ -22,6 +22,7 @@ CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_MMC=y
+CONFIG_CMD_PART=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_USB=y

configs/mx6sabresd_defconfig

@@ -23,6 +23,7 @@ CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_MMC=y
+CONFIG_CMD_PART=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_USB=y

include/configs/mx6sabre_common.h

@@ -77,7 +77,7 @@
 	"initrd_high=0xffffffff\0" \
 	"mmcdev=" __stringify(CONFIG_SYS_MMC_ENV_DEV) "\0" \
 	"mmcpart=1\0" \
-	"mmcroot=" CONFIG_MMCROOT " rootwait rw\0" \
+	"finduuid=part uuid mmc ${mmcdev}:2 uuid\0" \
 	"update_sd_firmware=" \
 		"if test ${ip_dyn} = yes; then " \
 			"setenv get_cmd dhcp; " \
@@ -93,7 +93,7 @@
 		"fi\0" \
 	EMMC_ENV	  \
 	"mmcargs=setenv bootargs console=${console},${baudrate} " \
-		"root=${mmcroot}\0" \
+		"root=PARTUUID=${uuid} rootwait rw\0" \
 	"loadbootscript=" \
 		"fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${script};\0" \
 	"bootscript=echo Running bootscript from mmc ...; " \
@@ -101,6 +101,7 @@
 	"loadimage=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${image}\0" \
 	"loadfdt=fatload mmc ${mmcdev}:${mmcpart} ${fdt_addr} ${fdt_file}\0" \
 	"mmcboot=echo Booting from mmc ...; " \
+		"run finduuid; " \
 		"run mmcargs; " \
 		"if test ${boot_fdt} = yes || test ${boot_fdt} = try; then " \
 			"if run loadfdt; then " \

include/configs/mx6sabreauto.h

@@ -16,7 +16,6 @@
 #define CONFIG_MACH_TYPE	3529
 #define CONFIG_MXC_UART_BASE	UART4_BASE
 #define CONSOLE_DEV		"ttymxc3"
-#define CONFIG_MMCROOT			"/dev/mmcblk0p2"
 
 /* USB Configs */
 #define CONFIG_USB_HOST_ETHER

include/configs/mx6sabresd.h

@@ -16,7 +16,6 @@
 #define CONFIG_MACH_TYPE	3980
 #define CONFIG_MXC_UART_BASE	UART1_BASE
 #define CONSOLE_DEV		"ttymxc0"
-#define CONFIG_MMCROOT			"/dev/mmcblk1p2"
 
 #define CONFIG_SUPPORT_EMMC_BOOT /* eMMC specific */