riscv: qemu: clear kernel-start/-end in device tree as workaround for BBL

QEMU specifies the location of Linux (supplied with the -kernel
argument) in the device tree using the riscv,kernel-start and
riscv,kernel-end properties. We currently rely on the SBI implementation
of BBL to run Linux and therefore embed Linux as payload in BBL. This
causes an issue, because BBL detects the kernel properties in the device
tree and ignores the Linux payload as a result.
Work around this issue by clearing the kernel properties in the device
tree before booting Linux.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

2 files changed, 40 insertions, 0 deletions

diff --git a/board/emulation/qemu-riscv/Kconfig b/board/emulation/qemu-riscv/Kconfig
index be5839b7db..33ca253432 100644
--- a/board/emulation/qemu-riscv/Kconfig
+++ b/board/emulation/qemu-riscv/Kconfig
@@ -30,5 +30,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	imply CMD_EXT4
 	imply CMD_FAT
 	imply BOARD_LATE_INIT
+	imply OF_BOARD_SETUP
 
 endif
diff --git a/board/emulation/qemu-riscv/qemu-riscv.c b/board/emulation/qemu-riscv/qemu-riscv.c
index 587f2c4909..d6167aaef1 100644
--- a/board/emulation/qemu-riscv/qemu-riscv.c
+++ b/board/emulation/qemu-riscv/qemu-riscv.c
@@ -48,3 +48,42 @@ int board_late_init(void)
 
 	return 0;
 }
+
+/*
+ * QEMU specifies the location of Linux (supplied with the -kernel argument)
+ * in the device tree using the riscv,kernel-start and riscv,kernel-end
+ * properties. We currently rely on the SBI implementation of BBL to run
+ * Linux and therefore embed Linux as payload in BBL. This causes an issue,
+ * because BBL detects the kernel properties in the device tree and ignores
+ * the Linux payload as a result. To work around this issue, we clear the
+ * kernel properties before booting Linux.
+ *
+ * This workaround can be removed, once we do not require BBL for its SBI
+ * implementation anymore.
+ */
+int ft_board_setup(void *blob, bd_t *bd)
+{
+	int chosen_offset, ret;
+
+	chosen_offset = fdt_path_offset(blob, "/chosen");
+	if (chosen_offset < 0)
+		return 0;
+
+#ifdef CONFIG_ARCH_RV64I
+	ret = fdt_setprop_u64(blob, chosen_offset, "riscv,kernel-start", 0);
+#else
+	ret = fdt_setprop_u32(blob, chosen_offset, "riscv,kernel-start", 0);
+#endif
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_ARCH_RV64I
+	ret = fdt_setprop_u64(blob, chosen_offset, "riscv,kernel-end", 0);
+#else
+	ret = fdt_setprop_u32(blob, chosen_offset, "riscv,kernel-end", 0);
+#endif
+	if (ret)
+		return ret;
+
+	return 0;
+}