riscv: add SPL support

U-Boot SPL on the generic RISC-V CPU supports two boot flows, directly
jumping to the image and via OpenSBI firmware. In the first case, both
U-Boot SPL and proper must be compiled to run in the same privilege
mode. Using OpenSBI firmware, U-Boot SPL must be compiled for machine
mode and U-Boot proper for supervisor mode.

To be able to use SPL, boards have to provide a supported SPL boot
device.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
diff --git a/arch/riscv/lib/spl.c b/arch/riscv/lib/spl.c
new file mode 100644
index 0000000..bea8695
--- /dev/null
+++ b/arch/riscv/lib/spl.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Fraunhofer AISEC,
+ * Lukas Auer <lukas.auer@aisec.fraunhofer.de>
+ */
+#include <common.h>
+#include <spl.h>
+#include <asm/smp.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+__weak void board_init_f(ulong dummy)
+{
+	int ret;
+
+	ret = spl_early_init();
+	if (ret)
+		panic("spl_early_init() failed: %d\n", ret);
+
+	arch_cpu_init_dm();
+
+	preloader_console_init();
+}
+
+void __noreturn jump_to_image_no_args(struct spl_image_info *spl_image)
+{
+	typedef void __noreturn (*image_entry_riscv_t)(ulong hart, void *dtb);
+	void *fdt_blob;
+	int ret;
+
+#if CONFIG_IS_ENABLED(LOAD_FIT) || CONFIG_IS_ENABLED(LOAD_FIT_FULL)
+	fdt_blob = spl_image->fdt_addr;
+#else
+	fdt_blob = (void *)gd->fdt_blob;
+#endif
+
+	image_entry_riscv_t image_entry =
+		(image_entry_riscv_t)spl_image->entry_point;
+	invalidate_icache_all();
+
+	debug("image entry point: 0x%lX\n", spl_image->entry_point);
+#ifdef CONFIG_SMP
+	ret = smp_call_function(spl_image->entry_point, (ulong)fdt_blob, 0);
+	if (ret)
+		hang();
+#endif
+	image_entry(gd->arch.boot_hart, fdt_blob);
+}