spl: support booting via RISC-V OpenSBI

RISC-V OpenSBI is an open-source implementation of the RISC-V Supervisor
Binary Interface (SBI) specification. It is required by Linux and U-Boot
running in supervisor mode. This patch adds support for booting via the
OpenSBI FW_DYNAMIC firmware. It supports OpenSBI version 0.4 and higher.

In this configuration, U-Boot SPL starts in machine mode. After loading
OpenSBI and U-Boot proper, it will start OpenSBI. All necessary
parameters are generated by U-Boot SPL and are passed to OpenSBI. U-Boot
proper is started in supervisor mode by OpenSBI. Support for OpenSBI is
enabled with CONFIG_SPL_OPENSBI. An additional configuration entry,
CONFIG_SPL_OPENSBI_LOAD_ADDR, is used to specify the load address of the
OpenSBI firmware binary. It is not used directly in U-Boot and instead
is intended to make the value available to scripts such as FIT
configuration generators.

The header file include/opensbi.h is based on header files from the
OpenSBI project. They are recent, as of commit bae54f764570 ("firmware:
Add fw_dynamic firmware").

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>

common/image.c

@@ -132,6 +132,7 @@ static const table_entry_t uimage_os[] = {
 #if defined(CONFIG_BOOTM_OPENRTOS) || defined(USE_HOSTCC)
 	{	IH_OS_OPENRTOS,	"openrtos",	"OpenRTOS",		},
 #endif
+	{	IH_OS_OPENSBI,	"opensbi",	"RISC-V OpenSBI",	},
 
 	{	-1,		"",		"",			},
 };

common/spl/Kconfig

@@ -1148,6 +1148,23 @@ config SPL_OPTEE
 	  OP-TEE is an open source Trusted OS  which is loaded by SPL.
 	  More detail at: https://github.com/OP-TEE/optee_os
 
+config SPL_OPENSBI
+	bool "Support RISC-V OpenSBI"
+	depends on RISCV && SPL_RISCV_MMODE && RISCV_SMODE
+	help
+	  OpenSBI is an open-source implementation of the RISC-V Supervisor Binary
+	  Interface (SBI) specification. U-Boot supports the OpenSBI FW_DYNAMIC
+	  firmware. It is loaded and started by U-Boot SPL.
+
+	  More details are available at https://github.com/riscv/opensbi and
+	  https://github.com/riscv/riscv-sbi-doc
+
+config SPL_OPENSBI_LOAD_ADDR
+	hex "OpenSBI load address"
+	depends on SPL_OPENSBI
+	help
+	  Load address of the OpenSBI binary.
+
 config TPL
 	bool
 	depends on SUPPORT_TPL

common/spl/Makefile

@@ -22,6 +22,7 @@ obj-$(CONFIG_$(SPL_TPL_)NET_SUPPORT) += spl_net.o
 obj-$(CONFIG_$(SPL_TPL_)MMC_SUPPORT) += spl_mmc.o
 obj-$(CONFIG_$(SPL_TPL_)ATF) += spl_atf.o
 obj-$(CONFIG_$(SPL_TPL_)OPTEE) += spl_optee.o
+obj-$(CONFIG_$(SPL_TPL_)OPENSBI) += spl_opensbi.o
 obj-$(CONFIG_$(SPL_TPL_)USB_STORAGE) += spl_usb.o
 obj-$(CONFIG_$(SPL_TPL_)FS_FAT) += spl_fat.o
 obj-$(CONFIG_$(SPL_TPL_)FS_EXT4) += spl_ext.o

common/spl/spl.c

@@ -659,6 +659,12 @@ void board_init_r(gd_t *dummy1, ulong dummy2)
 				(void *)spl_image.entry_point);
 		break;
 #endif
+#if CONFIG_IS_ENABLED(OPENSBI)
+	case IH_OS_OPENSBI:
+		debug("Jumping to U-Boot via RISC-V OpenSBI\n");
+		spl_invoke_opensbi(&spl_image);
+		break;
+#endif
 #ifdef CONFIG_SPL_OS_BOOT
 	case IH_OS_LINUX:
 		debug("Jumping to Linux\n");

common/spl/spl_opensbi.c

@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Fraunhofer AISEC,
+ * Lukas Auer <lukas.auer@aisec.fraunhofer.de>
+ *
+ * Based on common/spl/spl_atf.c
+ */
+#include <common.h>
+#include <errno.h>
+#include <spl.h>
+#include <asm/smp.h>
+#include <opensbi.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct fw_dynamic_info opensbi_info;
+
+static int spl_opensbi_find_uboot_node(void *blob, int *uboot_node)
+{
+	int fit_images_node, node;
+	const char *fit_os;
+
+	fit_images_node = fdt_path_offset(blob, "/fit-images");
+	if (fit_images_node < 0)
+		return -ENODEV;
+
+	fdt_for_each_subnode(node, blob, fit_images_node) {
+		fit_os = fdt_getprop(blob, node, FIT_OS_PROP, NULL);
+		if (!fit_os)
+			continue;
+
+		if (genimg_get_os_id(fit_os) == IH_OS_U_BOOT) {
+			*uboot_node = node;
+			return 0;
+		}
+	}
+
+	return -ENODEV;
+}
+
+void spl_invoke_opensbi(struct spl_image_info *spl_image)
+{
+	int ret, uboot_node;
+	ulong uboot_entry;
+	void (*opensbi_entry)(ulong hartid, ulong dtb, ulong info);
+
+	if (!spl_image->fdt_addr) {
+		pr_err("No device tree specified in SPL image\n");
+		hang();
+	}
+
+	/* Find U-Boot image in /fit-images */
+	ret = spl_opensbi_find_uboot_node(spl_image->fdt_addr, &uboot_node);
+	if (ret) {
+		pr_err("Can't find U-Boot node, %d", ret);
+		hang();
+	}
+
+	/* Get U-Boot entry point */
+	uboot_entry = fdt_getprop_u32(spl_image->fdt_addr, uboot_node,
+				      "entry-point");
+	if (uboot_entry == FDT_ERROR)
+		uboot_entry = fdt_getprop_u32(spl_image->fdt_addr, uboot_node,
+					      "load-addr");
+
+	/* Prepare obensbi_info object */
+	opensbi_info.magic = FW_DYNAMIC_INFO_MAGIC_VALUE;
+	opensbi_info.version = FW_DYNAMIC_INFO_VERSION;
+	opensbi_info.next_addr = uboot_entry;
+	opensbi_info.next_mode = FW_DYNAMIC_INFO_NEXT_MODE_S;
+	opensbi_info.options = SBI_SCRATCH_NO_BOOT_PRINTS;
+
+	opensbi_entry = (void (*)(ulong, ulong, ulong))spl_image->entry_point;
+	invalidate_icache_all();
+
+#ifdef CONFIG_SMP
+	ret = smp_call_function((ulong)spl_image->entry_point,
+				(ulong)spl_image->fdt_addr,
+				(ulong)&opensbi_info);
+	if (ret)
+		hang();
+#endif
+	opensbi_entry(gd->arch.boot_hart, (ulong)spl_image->fdt_addr,
+		      (ulong)&opensbi_info);
+}

include/image.h

@@ -156,6 +156,7 @@ enum {
 	IH_OS_OPENRTOS,		/* OpenRTOS	*/
 	IH_OS_ARM_TRUSTED_FIRMWARE,     /* ARM Trusted Firmware */
 	IH_OS_TEE,			/* Trusted Execution Environment */
+	IH_OS_OPENSBI,			/* RISC-V OpenSBI */
 
 	IH_OS_COUNT,
 };

include/opensbi.h

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (c) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Based on include/sbi/{fw_dynamic.h,sbi_scratch.h} from the OpenSBI project.
+ */
+#ifndef OPENSBI_H
+#define OPENSBI_H
+
+/** Expected value of info magic ('OSBI' ascii string in hex) */
+#define FW_DYNAMIC_INFO_MAGIC_VALUE		0x4942534f
+
+/** Maximum supported info version */
+#define FW_DYNAMIC_INFO_VERSION			0x1
+
+/** Possible next mode values */
+#define FW_DYNAMIC_INFO_NEXT_MODE_U		0x0
+#define FW_DYNAMIC_INFO_NEXT_MODE_S		0x1
+#define FW_DYNAMIC_INFO_NEXT_MODE_M		0x3
+
+enum sbi_scratch_options {
+	/** Disable prints during boot */
+	SBI_SCRATCH_NO_BOOT_PRINTS = (1 << 0),
+};
+
+/** Representation dynamic info passed by previous booting stage */
+struct fw_dynamic_info {
+	/** Info magic */
+	unsigned long magic;
+	/** Info version */
+	unsigned long version;
+	/** Next booting stage address */
+	unsigned long next_addr;
+	/** Next booting stage mode */
+	unsigned long next_mode;
+	/** Options for OpenSBI library */
+	unsigned long options;
+} __packed;
+
+#endif

include/spl.h

@@ -374,6 +374,11 @@ void spl_invoke_atf(struct spl_image_info *spl_image);
  */
 void spl_optee_entry(void *arg0, void *arg1, void *arg2, void *arg3);
 
+/**
+ * spl_invoke_opensbi - boot using a RISC-V OpenSBI image
+ */
+void spl_invoke_opensbi(struct spl_image_info *spl_image);
+
 /**
  * board_return_to_bootrom - allow for boards to continue with the boot ROM
  *