riscv: Provide a mechanism to fix DT for reserved memory

In RISC-V, M-mode software can reserve physical memory regions
by setting appropriate physical memory protection (PMP) csr. As the
PMP csr are accessible only in M-mode, S-mode U-Boot can not read
this configuration directly. However, M-mode software can pass this
information via reserved-memory node in device tree so that S-mode
software can access this information.

This patch provides a framework to copy to the reserved-memory node
from one DT to another. This will be used to update the DT used by
U-Boot and the DT passed to the next stage OS.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>

arch/riscv/cpu/start.S

@@ -119,6 +119,7 @@ call_board_init_f_0:
 
 	jal	board_init_f_init_reserve
 
+	SREG	s1, GD_FIRMWARE_FDT_ADDR(gp)
 	/* save the boot hart id to global_data */
 	SREG	tp, GD_BOOT_HART(gp)
 

arch/riscv/include/asm/global_data.h

@@ -15,6 +15,7 @@
 /* Architecture-specific global data */
 struct arch_global_data {
 	long boot_hart;		/* boot hart id */
+	phys_addr_t firmware_fdt_addr;
 #ifdef CONFIG_SIFIVE_CLINT
 	void __iomem *clint;	/* clint base address */
 #endif

arch/riscv/include/asm/u-boot-riscv.h

@@ -17,5 +17,7 @@ int cleanup_before_linux(void);
 /* board/.../... */
 int board_init(void);
 void board_quiesce_devices(void);
+int riscv_board_reserved_mem_fixup(void *fdt);
+int riscv_fdt_copy_resv_mem_node(const void *src_fdt, void *dest_fdt);
 
 #endif	/* _U_BOOT_RISCV_H_ */

arch/riscv/lib/Makefile

@@ -24,6 +24,7 @@ obj-y	+= reset.o
 obj-y   += setjmp.o
 obj-$(CONFIG_$(SPL_)SMP) += smp.o
 obj-$(CONFIG_SPL_BUILD)	+= spl.o
+obj-y   += fdt_fixup.o
 
 # For building EFI apps
 CFLAGS_$(EFI_CRT0) := $(CFLAGS_EFI)

arch/riscv/lib/asm-offsets.c

@@ -14,6 +14,7 @@
 int main(void)
 {
 	DEFINE(GD_BOOT_HART, offsetof(gd_t, arch.boot_hart));
+	DEFINE(GD_FIRMWARE_FDT_ADDR, offsetof(gd_t, arch.firmware_fdt_addr));
 #ifndef CONFIG_XIP
 	DEFINE(GD_AVAILABLE_HARTS, offsetof(gd_t, arch.available_harts));
 #endif

arch/riscv/lib/fdt_fixup.c

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates
+ *
+ */
+
+#include <common.h>
+#include <fdt_support.h>
+#include <mapmem.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/**
+ * riscv_fdt_copy_resv_mem_node() - Copy reserve memory node entry
+ * @src: Pointer to the source device tree from which reserved memory node
+ *	 needs to be copied.
+ * @dst: Pointer to the destination device tree to which reserved memory node
+ *	 needs to be copied.
+ *
+ * Return: 0 on success or if source doesn't have reserved memory node.
+ *	   Error if copy process failed.
+ */
+int riscv_fdt_copy_resv_mem_node(const void *src, void *dst)
+{
+	u32 phandle;
+	struct fdt_memory pmp_mem;
+	fdt_addr_t addr;
+	fdt_size_t size;
+	int offset, node, err, rmem_offset;
+	bool nomap = true;
+	char basename[32] = {0};
+	int bname_len;
+	int max_len = sizeof(basename);
+	const char *name;
+	char *temp;
+
+	offset = fdt_path_offset(src, "/reserved-memory");
+	if (offset < 0) {
+		printf("No reserved memory region found in source FDT\n");
+		return 0;
+	}
+
+	fdt_for_each_subnode(node, src, offset) {
+		name = fdt_get_name(src, node, NULL);
+
+		addr = fdtdec_get_addr_size_auto_noparent(src, node,
+							  "reg", 0, &size,
+							  false);
+		if (addr == FDT_ADDR_T_NONE) {
+			debug("failed to read address/size for %s\n", name);
+			continue;
+		}
+		strncpy(basename, name, max_len);
+		temp = strchr(basename, '@');
+		if (temp) {
+			bname_len = strnlen(basename, max_len) - strnlen(temp,
+								       max_len);
+			*(basename + bname_len) = '\0';
+		}
+		pmp_mem.start = addr;
+		pmp_mem.end = addr + size - 1;
+		err = fdtdec_add_reserved_memory(dst, basename, &pmp_mem,
+						 &phandle);
+		if (err < 0) {
+			printf("failed to add reserved memory: %d\n", err);
+			return err;
+		}
+		if (!fdt_getprop(src, node, "no-map", NULL))
+			nomap = false;
+		if (nomap) {
+			rmem_offset = fdt_node_offset_by_phandle(dst, phandle);
+			fdt_setprop_empty(dst, rmem_offset, "no-map");
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * riscv_board_reserved_mem_fixup() - Fix up reserved memory node for a board
+ * @fdt: Pointer to the device tree in which reserved memory node needs to be
+ *	 added.
+ *
+ * In RISC-V, any board compiled with OF_SEPARATE needs to copy the reserved
+ * memory node from the device tree provided by the firmware to the device tree
+ * used by U-Boot. This is a common function that individual board fixup
+ * functions can invoke.
+ *
+ * Return: 0 on success or error otherwise.
+ */
+int riscv_board_reserved_mem_fixup(void *fdt)
+{
+	int err;
+	void *src_fdt_addr;
+
+	src_fdt_addr = map_sysmem(gd->arch.firmware_fdt_addr, 0);
+	err = riscv_fdt_copy_resv_mem_node(src_fdt_addr, fdt);
+	if (err < 0)
+		return err;
+
+	return 0;
+}