riscv: Add SiFive FU540 board support

This patch adds SiFive FU540 board support. For now, only
SiFive serial, SiFive PRCI, and Cadance MACB drivers are
only enabled. The SiFive FU540 defconfig by default builds
U-Boot for S-Mode because U-Boot on SiFive FU540 will run
in S-Mode as payload of BBL or OpenSBI.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

board/sifive/fu540/Kconfig

@@ -0,0 +1,42 @@
+if TARGET_SIFIVE_FU540
+
+config SYS_BOARD
+	default "fu540"
+
+config SYS_VENDOR
+	default "sifive"
+
+config SYS_CPU
+	default "generic"
+
+config SYS_CONFIG_NAME
+	default "sifive-fu540"
+
+config SYS_TEXT_BASE
+	default 0x80000000 if !RISCV_SMODE
+	default 0x80200000 if RISCV_SMODE
+
+config BOARD_SPECIFIC_OPTIONS # dummy
+	def_bool y
+	select GENERIC_RISCV
+	imply CMD_DHCP
+	imply CMD_EXT2
+	imply CMD_EXT4
+	imply CMD_FAT
+	imply CMD_FS_GENERIC
+	imply CMD_NET
+	imply CMD_PING
+	imply CLK_SIFIVE
+	imply CLK_SIFIVE_FU540_PRCI
+	imply DOS_PARTITION
+	imply EFI_PARTITION
+	imply IP_DYN
+	imply ISO_PARTITION
+	imply MACB
+	imply MII
+	imply NET_RANDOM_ETHADDR
+	imply PHY_LIB
+	imply PHY_MSCC
+	imply SIFIVE_SERIAL
+
+endif

board/sifive/fu540/MAINTAINERS

@@ -0,0 +1,9 @@
+SiFive FU540 BOARD
+M:	Paul Walmsley <paul.walmsley@sifive.com>
+M:	Palmer Dabbelt <palmer@sifive.com>
+M:	Anup Patel <anup.patel@wdc.com>
+M:	Atish Patra <atish.patra@wdc.com>
+S:	Maintained
+F:	board/sifive/fu540/
+F:	include/configs/sifive-fu540.h
+F:	configs/sifive_fu540_defconfig

board/sifive/fu540/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2019 Western Digital Corporation or its affiliates.
+
+obj-y	+= fu540.o

board/sifive/fu540/fu540.c

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+
+int board_init(void)
+{
+	/* For now nothing to do here. */
+
+	return 0;
+}