am43xx_evm: add usb host boot support

While booting via usb host mode, ROM uses DMA to copy MLO over USB so
ARM internal RAM cannot be used. Adding USB host boot support by
introducing new config target which sets SPL_TEXT_BASE to OCMC ram.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

configs/am43xx_evm_usbhost_boot_defconfig

+CONFIG_ARM=y
+CONFIG_TARGET_AM43XX_EVM=y
+CONFIG_SPL=y
+CONFIG_SYS_EXTRA_OPTIONS="SERIAL1,CONS_INDEX=1,NAND,SPL_USB_HOST_SUPPORT"
+CONFIG_CMD_NET=y

include/configs/am43xx_evm.h

@@ -42,7 +42,16 @@
 #define CONFIG_POWER_TPS62362
 
 /* SPL defines. */
+#ifdef CONFIG_SPL_USB_HOST_SUPPORT
+/*
+ * For USB host boot, ROM uses DMA for copying MLO from USB storage
+ * and ARM internal ram is not accessible for DMA, so SPL text base
+ * should be in OCMC ram
+ */
+#define CONFIG_SPL_TEXT_BASE		0x40300350
+#else
 #define CONFIG_SPL_TEXT_BASE		0x402F4000
+#endif
 #define CONFIG_SPL_MAX_SIZE		(220 << 10)	/* 220KB */
 #define CONFIG_SYS_SPL_ARGS_ADDR	(CONFIG_SYS_SDRAM_BASE + \
 					 (128 << 20))
@@ -95,8 +104,8 @@
 #define CONFIG_SPL_LDSCRIPT		"$(CPUDIR)/omap-common/u-boot-spl.lds"
 
 /* SPL USB Support */
+#ifdef CONFIG_SPL_USB_HOST_SUPPORT
 #define CONFIG_SPL_USB_SUPPORT
-#define CONFIG_SPL_USB_HOST_SUPPORT
 #define CONFIG_SYS_USB_FAT_BOOT_PARTITION		1
 
 #define CONFIG_CMD_USB
@@ -108,6 +117,7 @@
 
 #define CONFIG_OMAP_USB_PHY
 #define CONFIG_AM437X_USB2PHY2_HOST
+#endif
 
 /* USB GADGET */
 #if !defined(CONFIG_SPL_BUILD) || \