[RFC PATCH 1/1] 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 EFI boot without
breaking the UEFI specification.

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>
---
 arch/riscv/lib/bootm.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c
index fad16901c5f2..b84cc2db2016 100644
--- a/arch/riscv/lib/bootm.c
+++ b/arch/riscv/lib/bootm.c
@@ -28,6 +28,19 @@ __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 accmodate new node");
+		return -1;
+	}
+	chosen_offset = fdt_path_offset(blob, "/chosen");
+	fdt_setprop_u64(blob, chosen_offset, "efi-boot-hartid",
+			   gd->arch.boot_hart);
+
 	return 0;
 }
 
-- 
2.24.0