Exynos5: Add support for USB download boot mode

Exynos5250 supports secondary USB device boot mode. If the iROM fails
to download u-boot from the primary boot device (such as SD or eMMC),
it will try to retrieve from the secondary boot device (such as USB).

Signed-off-by: Naveen Krishna Ch <ch.naveen@samsung.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

board/samsung/smdk5250/spl_boot.c

@@ -32,6 +32,21 @@ enum boot_mode {
 };
 
 	typedef u32 (*spi_copy_func_t)(u32 offset, u32 nblock, u32 dst);
+	typedef u32 (*usb_copy_func_t)(void);
+
+/*
+ * Set/clear program flow prediction and return the previous state.
+ */
+static int config_branch_prediction(int set_cr_z)
+{
+	unsigned int cr;
+
+	/* System Control Register: 11th bit Z Branch prediction enable */
+	cr = get_cr();
+	set_cr(set_cr_z ? cr | CR_Z : cr & ~CR_Z);
+
+	return cr & CR_Z;
+}
 
 /*
 * Copy U-boot from mmc to RAM:
@@ -41,10 +56,20 @@ enum boot_mode {
 void copy_uboot_to_ram(void)
 {
 	spi_copy_func_t spi_copy;
-	enum boot_mode bootmode;
+	usb_copy_func_t usb_copy;
+
+	int is_cr_z_set;
+	unsigned int sec_boot_check;
+	enum boot_mode bootmode = BOOT_MODE_OM;
 	u32 (*copy_bl2)(u32, u32, u32);
 
-	bootmode = readl(EXYNOS5_POWER_BASE) & OM_STAT;
+	/* Read iRAM location to check for secondary USB boot mode */
+	sec_boot_check = readl(EXYNOS_IRAM_SECONDARY_BASE);
+	if (sec_boot_check == EXYNOS_USB_SECONDARY_BOOT)
+		bootmode = BOOT_MODE_USB;
+
+	if (bootmode == BOOT_MODE_OM)
+		bootmode = readl(EXYNOS5_POWER_BASE) & OM_STAT;
 
 	switch (bootmode) {
 	case BOOT_MODE_SERIAL:
@@ -57,6 +82,17 @@ void copy_uboot_to_ram(void)
 		copy_bl2(BL2_START_OFFSET, BL2_SIZE_BLOC_COUNT,
 						CONFIG_SYS_TEXT_BASE);
 		break;
+	case BOOT_MODE_USB:
+		/*
+		 * iROM needs program flow prediction to be disabled
+		 * before copy from USB device to RAM
+		 */
+		is_cr_z_set = config_branch_prediction(0);
+		usb_copy = *(usb_copy_func_t *)
+				EXYNOS_COPY_USB_FNPTR_ADDR;
+		usb_copy();
+		config_branch_prediction(is_cr_z_set);
+		break;
 	default:
 		break;
 	}

include/configs/exynos5250-dt.h

@@ -134,6 +134,11 @@
 #define CONFIG_USB_EHCI_EXYNOS
 #define CONFIG_USB_STORAGE
 
+/* USB boot mode */
+#define EXYNOS_COPY_USB_FNPTR_ADDR	0x02020070
+#define EXYNOS_USB_SECONDARY_BOOT	0xfeed0002
+#define EXYNOS_IRAM_SECONDARY_BASE	0x02020018
+
 /* MMC SPL */
 #define CONFIG_SPL
 #define COPY_BL2_FNPTR_ADDR	0x02020030