[U-Boot] [PATCH 2/2] riscv: qemu-riscv.h: define CONFIG_PREBOOT (enables extlinux)

[David Abdurachmanov]

- Set fdt_addr variable, which is needed for extlinux to find FDT.
  Otherwise booting kernel using extlinux results in missing FDT.

- Also run fdt addr with FDT address so that fdt commands would
  work out of the box in U-Boot prompt.

This is successfully used by Fedora/RISCV with 5.1-rc3+ kernel using
OpenSBI -> U-Boot (S-mode) [extlinux] -> Kernel setup.

Signed-off-by: David Abdurachmanov <david.abdurachmanov at gmail.com>
---
 include/configs/qemu-riscv.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/configs/qemu-riscv.h b/include/configs/qemu-riscv.h
index 22a5cd7365..b7110edebc 100644
--- a/include/configs/qemu-riscv.h
+++ b/include/configs/qemu-riscv.h
@@ -48,4 +48,8 @@
 	"ramdisk_addr_r=0x88300000\0" \
 	BOOTENV
 
+#define CONFIG_PREBOOT \
+	"setenv fdt_addr ${fdtcontroladdr};" \
+	"fdt addr ${fdtcontroladdr};"
+
 #endif /* __CONFIG_H */
-- 
2.20.1