arm64: zynqmp: Print multiboot register value in EL3

Multi boot register can be used for using different boot images and design
better boot strategy. Let EL3 SPL or U-Boot to read it and print it.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/mach-zynqmp/include/mach/hardware.h

@@ -128,7 +128,9 @@ struct apu_regs {
 #define ZYNQMP_SILICON_VER_SHIFT	12
 
 struct csu_regs {
-	u32 reserved0[17];
+	u32 reserved0[4];
+	u32 multi_boot;
+	u32 reserved1[12];
 	u32 version;
 };
 

board/xilinx/zynqmp/zynqmp.c

@@ -328,6 +328,17 @@ int board_early_init_f(void)
 	return ret;
 }
 
+static int multi_boot(void)
+{
+	u32 multiboot;
+
+	multiboot = readl(&csu_base->multi_boot);
+
+	printf("Multiboot:\t%x\n", multiboot);
+
+	return 0;
+}
+
 int board_init(void)
 {
 	struct udevice *dev;
@@ -356,6 +367,9 @@ int board_init(void)
 	}
 #endif
 
+	if (current_el() == 3)
+		multi_boot();
+
 	return 0;
 }