rockchip: rk322x: enable fastboot to set boot mode tag

To support fastboot "fastboot reboot-bootloader" cmd.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/mach-rockchip/rk322x-board.c

@@ -7,6 +7,7 @@
 #include <clk.h>
 #include <dm.h>
 #include <ram.h>
+#include <syscon.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/periph.h>
@@ -136,3 +137,17 @@ int board_usb_cleanup(int index, enum usb_init_type init)
 	return 0;
 }
 #endif
+
+#if defined(CONFIG_USB_FUNCTION_FASTBOOT)
+int fb_set_reboot_flag(void)
+{
+	struct rk322x_grf *grf;
+
+	printf("Setting reboot to fastboot flag ...\n");
+	grf = syscon_get_first_range(ROCKCHIP_SYSCON_GRF);
+	/* Set boot mode to fastboot */
+	writel(BOOT_FASTBOOT, &grf->os_reg[0]);
+
+	return 0;
+}
+#endif