omap3_beagle: support findfdt and loadfdt for devicetree support

For folks not using concatenated device tree with uImage, having
an handy function to find and load device tree is very handy.

So introduce findfdt and loadfdt and run findfdt by default to make
it easier on user scripts.

Signed-off-by: Nishanth Menon <nm@ti.com>

include/configs/omap3_beagle.h

@@ -194,6 +194,8 @@
 #define CONFIG_EXTRA_ENV_SETTINGS \
 	"loadaddr=0x80200000\0" \
 	"rdaddr=0x81000000\0" \
+	"fdt_high=0xffffffff\0" \
+	"fdtaddr=0x80f80000\0" \
 	"usbtty=cdc_acm\0" \
 	"bootfile=uImage\0" \
 	"ramdisk=ramdisk.gz\0" \
@@ -234,6 +236,17 @@
 		"omapdss.def_disp=${defaultdisplay} " \
 		"root=${nandroot} " \
 		"rootfstype=${nandrootfstype}\0" \
+	"findfdt=" \
+		"if test $beaglerev = AxBx; then " \
+			"setenv fdtfile omap3-beagle.dtb; fi; " \
+		"if test $beaglerev = Cx; then " \
+			"setenv fdtfile omap3-beagle.dtb; fi; " \
+		"if test $beaglerev = xMAB; then " \
+			"setenv fdtfile omap3-beagle-xm.dtb; fi; " \
+		"if test $beaglerev = xMC; then " \
+			"setenv fdtfile omap3-beagle-xm.dtb; fi; " \
+		"if test $fdtfile = undefined; then " \
+			"echo WARNING: Could not determine device tree to use; fi; \0" \
 	"bootenv=uEnv.txt\0" \
 	"loadbootenv=fatload mmc ${mmcdev} ${loadaddr} ${bootenv}\0" \
 	"importbootenv=echo Importing environment from mmc ...; " \
@@ -249,6 +262,7 @@
 		"rootfstype=${ramrootfstype}\0" \
 	"loadramdisk=load mmc ${bootpart} ${rdaddr} ${bootdir}/${ramdisk}\0" \
 	"loadimage=load mmc ${bootpart} ${loadaddr} ${bootdir}/${bootfile}\0" \
+	"loadfdt=load mmc ${bootpart} ${fdtaddr} ${bootdir}/${fdtfile}\0" \
 	"mmcboot=echo Booting from mmc ...; " \
 		"run mmcargs; " \
 		"bootm ${loadaddr}\0" \
@@ -265,6 +279,7 @@
 	"userbutton_nonxm=gpio input 7;\0"
 /* "run userbutton" will return 1 (false) if pressed and 0 (true) if not */
 #define CONFIG_BOOTCOMMAND \
+	"run findfdt; " \
 	"mmc dev ${mmcdev}; if mmc rescan; then " \
 		"if run userbutton; then " \
 			"setenv bootenv uEnv.txt;" \