RISC-V: add generic DT image

This barebox image implements the same header as Linux and receives
the device tree in the same register. It can be booted from barebox
or loaded by Qemu -kernel option.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 46 insertions, 0 deletions

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 08a0e7cef4..e630ad4ceb 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -73,6 +73,15 @@ config 64BIT
 
 source "arch/riscv/mach-erizo/Kconfig"
 
+config BOARD_RISCV_GENERIC_DT
+	select BOARD_GENERIC_DT
+	bool "Build generic RISC-V device tree 2nd stage image"
+	help
+	  This enables compilation of a generic image that can be started 2nd
+	  stage from barebox or from qemu. It picks up a device tree passed
+	  in a1 like the Kernel does, so it could be used anywhere where a Kernel
+	  image could be used. The image will be called images/barebox-dt-2nd.img
+
 endmenu
 
 menu "RISC-V specific settings"
diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
index 70e5b11beb..968a826d16 100644
--- a/arch/riscv/boot/Makefile
+++ b/arch/riscv/boot/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-y += start.o
 pbl-y += entry.o uncompress.o
+pbl-$(CONFIG_BOARD_GENERIC_DT) += board-dt-2nd.o
diff --git a/arch/riscv/boot/board-dt-2nd.c b/arch/riscv/boot/board-dt-2nd.c
new file mode 100644
index 0000000000..25fa7d4f2b
--- /dev/null
+++ b/arch/riscv/boot/board-dt-2nd.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <common.h>
+#include <debug_ll.h>
+#include <pbl.h>
+
+#if __riscv_xlen == 64
+#define IMAGE_LOAD_OFFSET 0x200000 /* Image load offset(2MB) from start of RAM */
+#else
+#define IMAGE_LOAD_OFFSET 0x400000 /* Image load offset(4MB) from start of RAM */
+#endif
+
+/* because we can depend on being loaded at an offset, we can just use
+ * our load address as stack top
+ */
+#define __barebox_riscv_head() \
+	__barebox_riscv_header("auipc sp, 0", IMAGE_LOAD_OFFSET, \
+			       RISCV_HEADER_VERSION, "RISCV", RISCV_IMAGE_MAGIC2)
+
+#include <asm/barebox-riscv.h>
+
+ENTRY_FUNCTION(start_dt_2nd, a0, _fdt, a2)
+{
+	unsigned long membase, memsize;
+	void *fdt = (void *)_fdt;
+
+	if (!fdt)
+		hang();
+
+	relocate_to_current_adr();
+	setup_c();
+
+	fdt_find_mem(fdt, &membase, &memsize);
+
+	barebox_riscv_entry(membase, memsize, fdt);
+}