riscv: sifive: fu540: add SPL configuration

Add a support for SPL which will boot from L2 LIM (0x0800_0000) and
then SPL will boot U-Boot FIT image (OpenSBI FW_DYNAMIC + u-boot.bin)
from MMC boot devices.

SPL related code is leveraged from FSBL
(https://github.com/sifive/freedom-u540-c000-bootloader.git)

Signed-off-by: Pragnesh Patel <pragnesh.patel@sifive.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>

arch/riscv/cpu/fu540/Makefile

@@ -3,5 +3,9 @@
 # Copyright (C) 2020 SiFive, Inc
 # Pragnesh Patel <pragnesh.patel@sifive.com>
 
+ifeq ($(CONFIG_SPL_BUILD),y)
+obj-y += spl.o
+else
 obj-y += dram.o
 obj-y += cpu.o
+endif

arch/riscv/cpu/fu540/spl.c

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 SiFive, Inc
+ * Pragnesh Patel <pragnesh.patel@sifive.com>
+ */
+
+#include <dm.h>
+#include <log.h>
+
+int soc_spl_init(void)
+{
+	int ret;
+	struct udevice *dev;
+
+	/* DDR init */
+	ret = uclass_get_device(UCLASS_RAM, 0, &dev);
+	if (ret) {
+		debug("DRAM init failed: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}

arch/riscv/dts/hifive-unleashed-a00-u-boot.dtsi

@@ -4,6 +4,7 @@
  */
 
 #include "fu540-c000-u-boot.dtsi"
+#include "fu540-hifive-unleashed-a00-ddr.dtsi"
 
 / {
 	aliases {
@@ -26,3 +27,7 @@
 		u-boot,dm-spl;
 	};
 };
+
+&gpio {
+	u-boot,dm-spl;
+};

arch/riscv/include/asm/arch-fu540/spl.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2020 SiFive, Inc.
+ *
+ * Authors:
+ *   Pragnesh Patel <pragnesh.patel@sifve.com>
+ */
+
+#ifndef _SPL_SIFIVE_H
+#define _SPL_SIFIVE_H
+
+int soc_spl_init(void);
+
+#endif /* _SPL_SIFIVE_H */