[PATCH v3 1/5] riscv: Add boot hartid to Device tree

[Atish Patra]

Linux booting protocol mandates that register "a0" contains the hartid.
However, U-boot can not pass the hartid via a0 during via standard UEFI
protocol. DT nodes are commonly used to pass such information to the OS.

Add a DT node under chosen node to indicate the boot hartid. EFI stub
in Linux kernel will parse this node and pass it to the real kernel
in "a0" before jumping to it.

Signed-off-by: Atish Patra <atish.patra at wdc.com>
Reviewed-by: Rick Chen <rick at andestech.com>
---
 arch/riscv/lib/bootm.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c
index fad16901c5f2..f927694ae32f 100644
--- a/arch/riscv/lib/bootm.c
+++ b/arch/riscv/lib/bootm.c
@@ -28,6 +28,28 @@ __weak void board_quiesce_devices(void)
 
 int arch_fixup_fdt(void *blob)
 {
+	u32 size;
+	int chosen_offset, err;
+
+	size = fdt_totalsize(blob);
+	err  = fdt_open_into(blob, blob, size + 32);
+	if (err < 0) {
+		printf("Device Tree can't be expanded to accommodate new node");
+		return -1;
+	}
+	chosen_offset = fdt_path_offset(blob, "/chosen");
+	if (chosen_offset < 0) {
+		err = fdt_add_subnode(blob, 0, "chosen");
+		if (err < 0) {
+			printf("chosen node can not be added\n");
+			return -1;
+		}
+	}
+
+	/* Overwrite the boot-hartid as U-Boot is the last state BL */
+	fdt_setprop_u32(blob, chosen_offset, "boot-hartid",
+			   gd->arch.boot_hart);
+
 	return 0;
 }
 
-- 
2.25.1