platform: Add generic FDT based platform support

We add generic FDT based platform support which provides platform
specific functionality based on the FDT passed by previous booting
stage.

By default, the generic FDT platform makes following assumptions:
1. platform FW_TEXT_START is 0x80000000
2. platform features are default
3. platform stack size is default
4. platform has no quirks or work-arounds

The above assumptions (except 1) can be overridden by adding special
platform callbacks which will be called based on the FDT root node
compatible string.

By default, we compile OpenSBI generic platform as follows:
$ make PLATFORM=generic

For a non-standard FW_TEXT_START, we can compile OpenSBI generic
platform as follows:
$ make PLATFORM=generic FW_TEXT_START=<non_standard_text_start>

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

docs/platform/generic.md

@@ -0,0 +1,42 @@
+Generic Platform
+================
+
+The **Generic** platform is a flattened device tree (FDT) based platform
+where all platform specific functionality is provided based on FDT passed
+by previous booting stage. The **Generic** platform allows us to use same
+OpenSBI firmware binaries on various emulators, simulators, FPGAs, and
+boards.
+
+By default, the generic FDT platform makes following assumptions:
+
+1. platform FW_TEXT_START is 0x80000000
+2. platform features are default
+3. platform stack size is default
+4. platform has no quirks or work-arounds
+
+The above assumptions (except 1) can be overridden by adding special platform
+callbacks which will be called based on FDT root node compatible string.
+
+Users of the generic FDT platform will have to ensure that:
+
+1. Various FDT based drivers under lib/utils directory are upto date
+   based on their platform requirements
+2. The FDT passed by previous booting stage has DT compatible strings and
+   DT properties in sync with the FDT based drivers under lib/utils directory
+
+To build the platform-specific library and firmware images, provide the
+*PLATFORM=generic* parameter to the top level `make` command.
+
+For custom FW_TEXT_START, we can build the platform-specific library and
+firmware images by passing *PLATFORM=generic FW_TEXT_START=<custom_text_start>*
+parameter to the top level `make` command.
+
+Platform Options
+----------------
+
+The *Generic* platform does not have any platform-specific options.
+
+RISC-V Platforms Using Generic Platform
+---------------------------------------
+
+To be added later.

docs/platform/platform.md

@@ -3,6 +3,11 @@ OpenSBI Supported Platforms
 
 OpenSBI currently supports the following virtual and hardware platforms:
 
+* **Generic**: Flattened device tree (FDT) based platform where platform
+  specific functionality is provided based on the FDT passed by previous
+  booting stage. More details on this platform can be found in the file
+  *[generic.md]*.
+
 * **QEMU RISC-V Virt Machine**: Platform support for the QEMU *virt* virtual
   RISC-V machine. This virtual machine is intended for RISC-V software
   development and tests. More details on this platform can be found in the
@@ -34,6 +39,7 @@ template files for implementing support for a new platform. The *object.mk*,
 *config.mk* and *platform.c* template files provides enough comments to
 facilitate the implementation.
 
+[generic.md]: generic.md
 [qemu_virt.md]: qemu_virt.md
 [sifive_fu540.md]: sifive_fu540.md
 [fpga-ariane.md]: fpga-ariane.md

platform/generic/config.mk

@@ -0,0 +1,40 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2020 Western Digital Corporation or its affiliates.
+#
+# Authors:
+#   Anup Patel <anup.patel@wdc.com>
+#
+
+# Compiler flags
+platform-cppflags-y =
+platform-cflags-y =
+platform-asflags-y =
+platform-ldflags-y =
+
+# Command for platform specific "make run"
+platform-runcmd = qemu-system-riscv$(PLATFORM_RISCV_XLEN) -M virt -m 256M \
+  -nographic -kernel $(build_dir)/platform/generic/firmware/fw_payload.elf
+
+# Blobs to build
+FW_TEXT_START=0x80000000
+FW_DYNAMIC=y
+FW_JUMP=y
+ifeq ($(PLATFORM_RISCV_XLEN), 32)
+  # This needs to be 4MB aligned for 32-bit system
+  FW_JUMP_ADDR=$(shell printf "0x%X" $$(($(FW_TEXT_START) + 0x400000)))
+else
+  # This needs to be 2MB aligned for 64-bit system
+  FW_JUMP_ADDR=$(shell printf "0x%X" $$(($(FW_TEXT_START) + 0x200000)))
+endif
+FW_JUMP_FDT_ADDR=$(shell printf "0x%X" $$(($(FW_TEXT_START) + 0x2200000)))
+FW_PAYLOAD=y
+ifeq ($(PLATFORM_RISCV_XLEN), 32)
+  # This needs to be 4MB aligned for 32-bit system
+  FW_PAYLOAD_OFFSET=0x400000
+else
+  # This needs to be 2MB aligned for 64-bit system
+  FW_PAYLOAD_OFFSET=0x200000
+endif
+FW_PAYLOAD_FDT_ADDR=$(FW_JUMP_FDT_ADDR)

platform/generic/include/platform_override.h

@@ -0,0 +1,26 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ */
+
+#ifndef __PLATFORM_OVERRIDE_H__
+#define __PLATFORM_OVERRIDE_H__
+
+#include <sbi/sbi_types.h>
+
+struct platform_override {
+	const struct fdt_match *match_table;
+	u64 (*features)(const struct fdt_match *match);
+	u64 (*tlbr_flush_limit)(const struct fdt_match *match);
+	int (*early_init)(bool cold_boot, const struct fdt_match *match);
+	int (*final_init)(bool cold_boot, const struct fdt_match *match);
+	void (*early_exit)(const struct fdt_match *match);
+	void (*final_exit)(const struct fdt_match *match);
+	int (*system_reset)(u32 reset_type, const struct fdt_match *match);
+};
+
+#endif

platform/generic/objects.mk

@@ -0,0 +1,10 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2020 Western Digital Corporation or its affiliates.
+#
+# Authors:
+#   Anup Patel <anup.patel@wdc.com>
+#
+
+platform-objs-y += platform.o

platform/generic/platform.c

@@ -0,0 +1,209 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ */
+
+#include <libfdt.h>
+#include <platform_override.h>
+#include <sbi/riscv_asm.h>
+#include <sbi/sbi_hartmask.h>
+#include <sbi/sbi_platform.h>
+#include <sbi/sbi_string.h>
+#include <sbi_utils/fdt/fdt_fixup.h>
+#include <sbi_utils/fdt/fdt_helper.h>
+#include <sbi_utils/irqchip/fdt_irqchip.h>
+#include <sbi_utils/serial/fdt_serial.h>
+#include <sbi_utils/timer/fdt_timer.h>
+#include <sbi_utils/ipi/fdt_ipi.h>
+#include <sbi_utils/reset/fdt_reset.h>
+
+static const struct platform_override *special_platforms[] = { };
+
+static const struct platform_override *generic_plat = NULL;
+static const struct fdt_match *generic_plat_match = NULL;
+
+static void fw_platform_lookup_special(void *fdt, int root_offset)
+{
+	int pos, noff;
+	const struct platform_override *plat;
+	const struct fdt_match *match;
+
+	for (pos = 0; pos < array_size(special_platforms); pos++) {
+		plat = special_platforms[pos];
+		if (!plat->match_table)
+			continue;
+
+		noff = fdt_find_match(fdt, plat->match_table, &match);
+		if (noff < 0)
+			continue;
+
+		generic_plat = plat;
+		generic_plat_match = match;
+		break;
+	}
+}
+
+extern struct sbi_platform platform;
+static u32 generic_hart_index2id[SBI_HARTMASK_MAX_BITS] = { 0 };
+
+/*
+ * The fw_platform_init() function is called very early on the boot HART
+ * OpenSBI reference firmwares so that platform specific code get chance
+ * to update "platform" instance before it is used.
+ *
+ * The arguments passed to fw_platform_init() function are boot time state
+ * of A0 to A4 register. The "arg0" will be boot HART id and "arg1" will
+ * be address of FDT passed by previous booting stage.
+ */
+void fw_platform_init(unsigned long arg0, unsigned long arg1,
+		      unsigned long arg2, unsigned long arg3,
+		      unsigned long arg4)
+{
+	const char *model, *mmu_type;
+	void *fdt = (void *)arg1;
+	u32 hartid, hart_count = 0;
+	int rc, root_offset, cpus_offset, cpu_offset, len;
+
+	root_offset = fdt_path_offset(fdt, "/");
+	if (root_offset < 0)
+		goto fail;
+
+	fw_platform_lookup_special(fdt, root_offset);
+
+	model = fdt_getprop(fdt, root_offset, "model", &len);
+	if (model)
+		sbi_strncpy(platform.name, model, sizeof(platform.name));
+
+	if (generic_plat && generic_plat->features)
+		platform.features = generic_plat->features(generic_plat_match);
+
+	cpus_offset = fdt_path_offset(fdt, "/cpus");
+	if (cpus_offset < 0)
+		goto fail;
+
+	fdt_for_each_subnode(cpu_offset, fdt, cpus_offset) {
+		rc = fdt_parse_hart_id(fdt, cpu_offset, &hartid);
+		if (rc)
+			continue;
+
+		if (SBI_HARTMASK_MAX_BITS <= hartid)
+			continue;
+
+		mmu_type = fdt_getprop(fdt, cpu_offset, "mmu-type", &len);
+		if (!mmu_type || !len)
+			hartid = -1U;
+
+		generic_hart_index2id[hart_count++] = hartid;
+	}
+
+	platform.hart_count = hart_count;
+
+	return;
+
+fail:
+	while (1)
+		wfi();
+}
+
+static int generic_early_init(bool cold_boot)
+{
+	int rc;
+
+	if (generic_plat && generic_plat->early_init) {
+		rc = generic_plat->early_init(cold_boot, generic_plat_match);
+		if (rc)
+			return rc;
+	}
+
+	if (!cold_boot)
+		return 0;
+
+	return fdt_reset_init();
+}
+
+static int generic_final_init(bool cold_boot)
+{
+	void *fdt;
+	int rc;
+
+	if (generic_plat && generic_plat->final_init) {
+		rc = generic_plat->final_init(cold_boot, generic_plat_match);
+		if (rc)
+			return rc;
+	}
+
+	if (!cold_boot)
+		return 0;
+
+	fdt = sbi_scratch_thishart_arg1_ptr();
+
+	fdt_cpu_fixup(fdt);
+	fdt_fixups(fdt);
+
+	return 0;
+}
+
+static void generic_early_exit(void)
+{
+	if (generic_plat && generic_plat->early_exit)
+		generic_plat->early_exit(generic_plat_match);
+}
+
+static void generic_final_exit(void)
+{
+	if (generic_plat && generic_plat->final_exit)
+		generic_plat->final_exit(generic_plat_match);
+}
+
+static u64 generic_tlbr_flush_limit(void)
+{
+	if (generic_plat && generic_plat->tlbr_flush_limit)
+		return generic_plat->tlbr_flush_limit(generic_plat_match);
+	return SBI_PLATFORM_TLB_RANGE_FLUSH_LIMIT_DEFAULT;
+}
+
+static int generic_system_reset(u32 reset_type)
+{
+	if (generic_plat && generic_plat->system_reset)
+		return generic_plat->system_reset(reset_type,
+						  generic_plat_match);
+	return fdt_system_reset(reset_type);
+}
+
+const struct sbi_platform_operations platform_ops = {
+	.early_init		= generic_early_init,
+	.final_init		= generic_final_init,
+	.early_exit		= generic_early_exit,
+	.final_exit		= generic_final_exit,
+	.console_putc		= fdt_serial_putc,
+	.console_getc		= fdt_serial_getc,
+	.console_init		= fdt_serial_init,
+	.irqchip_init		= fdt_irqchip_init,
+	.irqchip_exit		= fdt_irqchip_exit,
+	.ipi_send		= fdt_ipi_send,
+	.ipi_clear		= fdt_ipi_clear,
+	.ipi_init		= fdt_ipi_init,
+	.ipi_exit		= fdt_ipi_exit,
+	.get_tlbr_flush_limit	= generic_tlbr_flush_limit,
+	.timer_value		= fdt_timer_value,
+	.timer_event_stop	= fdt_timer_event_stop,
+	.timer_event_start	= fdt_timer_event_start,
+	.timer_init		= fdt_timer_init,
+	.timer_exit		= fdt_timer_exit,
+	.system_reset		= generic_system_reset,
+};
+
+struct sbi_platform platform = {
+	.opensbi_version	= OPENSBI_VERSION,
+	.platform_version	= SBI_PLATFORM_VERSION(0x0, 0x01),
+	.name			= "Generic",
+	.features		= SBI_PLATFORM_DEFAULT_FEATURES,
+	.hart_count		= SBI_HARTMASK_MAX_BITS,
+	.hart_index2id		= generic_hart_index2id,
+	.hart_stack_size	= SBI_PLATFORM_DEFAULT_HART_STACK_SIZE,
+	.platform_ops_addr	= (unsigned long)&platform_ops
+};