From: Anup Patel <anup.patel@wdc.com>

Extend sifive_u machine to allow passing custom DTB using "-dtb"
command-line parameter. This will help users pass modified DTB
or Linux SiFive DTB to sifive_u machine.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20201022053225.2596110-1-anup.patel@wdc.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 hw/riscv/sifive_u.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
index b2472c6627..2f19a9cda2 100644
--- a/hw/riscv/sifive_u.c
+++ b/hw/riscv/sifive_u.c
@@ -100,14 +100,25 @@ static void create_fdt(SiFiveUState *s, const struct MemmapEntry *memmap,
     int cpu;
     uint32_t *cells;
     char *nodename;
+    const char *dtb_filename;
     char ethclk_names[] = "pclk\0hclk";
     uint32_t plic_phandle, prci_phandle, gpio_phandle, phandle = 1;
     uint32_t hfclk_phandle, rtcclk_phandle, phy_phandle;
 
-    fdt = s->fdt = create_device_tree(&s->fdt_size);
-    if (!fdt) {
-        error_report("create_device_tree() failed");
-        exit(1);
+    dtb_filename = qemu_opt_get(qemu_get_machine_opts(), "dtb");
+    if (dtb_filename) {
+        fdt = s->fdt = load_device_tree(dtb_filename, &s->fdt_size);
+        if (!fdt) {
+            error_report("load_device_tree() failed");
+            exit(1);
+        }
+        goto update_bootargs;
+    } else {
+        fdt = s->fdt = create_device_tree(&s->fdt_size);
+        if (!fdt) {
+            error_report("create_device_tree() failed");
+            exit(1);
+        }
     }
 
     qemu_fdt_setprop_string(fdt, "/", "model", "SiFive HiFive Unleashed A00");
@@ -390,13 +401,14 @@ static void create_fdt(SiFiveUState *s, const struct MemmapEntry *memmap,
 
     qemu_fdt_add_subnode(fdt, "/chosen");
     qemu_fdt_setprop_string(fdt, "/chosen", "stdout-path", nodename);
-    if (cmdline) {
-        qemu_fdt_setprop_string(fdt, "/chosen", "bootargs", cmdline);
-    }
-
     qemu_fdt_setprop_string(fdt, "/aliases", "serial0", nodename);
 
     g_free(nodename);
+
+update_bootargs:
+    if (cmdline) {
+        qemu_fdt_setprop_string(fdt, "/chosen", "bootargs", cmdline);
+    }
 }
 
 static void sifive_u_machine_reset(void *opaque, int n, int level)
-- 
2.28.0