[PATCH v2 3/4] riscv: Provide a mechanism for riscv boards to parse reserved memory

[Atish Patra]

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.

In U-boot, any board may use the DT in following ways.
1. OF_SEPARTE: It ignores the DT from previous stage and uses the DT
from U-Boot sources.
2. OF_PRIOR_STATE: It reuses the DT from previous stage.
For case 1: U-Boot needs to parse the reserved-memory node from the
DT passed from the previous stage and update the DT in use.

This patch provides a framework to do that from any RISC-V boards.

Signed-off-by: Atish Patra <atish.patra at wdc.com>
---
 arch/riscv/cpu/start.S                |  1 +
 arch/riscv/include/asm/global_data.h  |  1 +
 arch/riscv/include/asm/u-boot-riscv.h |  1 +
 arch/riscv/lib/asm-offsets.c          |  1 +
 arch/riscv/lib/bootm.c                | 37 +++++++++++++++++++++++++++
 5 files changed, 41 insertions(+)

diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
index 6b3ff99c3882..0282685c2906 100644
--- a/arch/riscv/cpu/start.S
+++ b/arch/riscv/cpu/start.S
@@ -121,6 +121,7 @@ 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)
 
diff --git a/arch/riscv/include/asm/global_data.h b/arch/riscv/include/asm/global_data.h
index b74bd7e738bb..51ac8d1c98e2 100644
--- a/arch/riscv/include/asm/global_data.h
+++ b/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
diff --git a/arch/riscv/include/asm/u-boot-riscv.h b/arch/riscv/include/asm/u-boot-riscv.h
index 49febd588102..b7bea0ba184d 100644
--- a/arch/riscv/include/asm/u-boot-riscv.h
+++ b/arch/riscv/include/asm/u-boot-riscv.h
@@ -17,5 +17,6 @@ int cleanup_before_linux(void);
 /* board/.../... */
 int board_init(void);
 void board_quiesce_devices(void);
+int riscv_board_reserved_mem_fixup(void *fdt);
 
 #endif	/* _U_BOOT_RISCV_H_ */
diff --git a/arch/riscv/lib/asm-offsets.c b/arch/riscv/lib/asm-offsets.c
index 4fa4fd371473..7301c1b98e23 100644
--- a/arch/riscv/lib/asm-offsets.c
+++ b/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
diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c
index f927694ae32f..3a4d0bf14c86 100644
--- a/arch/riscv/lib/bootm.c
+++ b/arch/riscv/lib/bootm.c
@@ -19,6 +19,7 @@
 #include <dm/device.h>
 #include <dm/root.h>
 #include <u-boot/zlib.h>
+#include <mapmem.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -26,6 +27,42 @@ __weak void board_quiesce_devices(void)
 {
 }
 
+int riscv_board_reserved_mem_fixup(void *fdt)
+{
+	uint32_t phandle;
+	struct fdt_memory pmp_mem;
+	int err;
+	void *src_fdt_addr;
+	int offset, node;
+	phys_addr_t addr, size;
+
+	src_fdt_addr = map_sysmem(gd->arch.firmware_fdt_addr, 0);
+	offset = fdt_path_offset(src_fdt_addr, "/reserved-memory");
+	if (offset < 0) {
+		printf("No reserved memory region found in FDT\n");
+		return offset;
+	}
+
+	fdt_for_each_subnode(node, src_fdt_addr, offset) {
+		const char *name = fdt_get_name(src_fdt_addr, node, NULL);
+
+		addr = fdtdec_get_addr_size(src_fdt_addr, node, "reg", &size);
+		if (addr == FDT_ADDR_T_NONE) {
+			debug("failed to read address/size for %s\n", name);
+			continue;
+		}
+		pmp_mem.start = addr;
+		pmp_mem.end = addr + size;
+		err = fdtdec_add_reserved_memory(fdt, name, &pmp_mem, &phandle);
+		if (err < 0) {
+			printf("failed to add reserved memory: %d\n", err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 int arch_fixup_fdt(void *blob)
 {
 	u32 size;
-- 
2.25.1