1 files changed, 56 insertions, 0 deletions

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index a6f83ea107ae..1fbeab27075f 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -21,6 +21,7 @@
 #include <linux/slab.h>
 #include <linux/libfdt.h>
 #include <linux/debugfs.h>
+#include <linux/serial_core.h>
 
 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>
@@ -696,6 +697,61 @@ static inline void early_init_dt_check_for_initrd(unsigned long node)
 }
 #endif /* CONFIG_BLK_DEV_INITRD */
 
+#ifdef CONFIG_SERIAL_EARLYCON
+extern struct of_device_id __earlycon_of_table[];
+
+int __init early_init_dt_scan_chosen_serial(void)
+{
+        int offset;
+        const char *p;
+        int l;
+        const struct of_device_id *match = __earlycon_of_table;
+        const void *fdt = initial_boot_params;
+
+        offset = fdt_path_offset(fdt, "/chosen");
+        if (offset < 0)
+                offset = fdt_path_offset(fdt, "/chosen@0");
+        if (offset < 0)
+                return -ENOENT;
+
+        p = fdt_getprop(fdt, offset, "stdout-path", &l);
+        if (!p)
+                p = fdt_getprop(fdt, offset, "linux,stdout-path", &l);
+        if (!p || !l)
+                return -ENOENT;
+
+        /* Get the node specified by stdout-path */
+        offset = fdt_path_offset(fdt, p);
+        if (offset < 0)
+                return -ENODEV;
+
+        while (match->compatible) {
+                unsigned long addr;
+                if (fdt_node_check_compatible(fdt, offset, match->compatible)) {
+                        match++;
+                        continue;
+                }
+
+                addr = fdt_translate_address(fdt, offset);
+                if (!addr)
+                        return -ENXIO;
+
+                of_setup_earlycon(addr, match->data);
+                return 0;
+        }
+        return -ENODEV;
+}
+
+static int __init setup_of_earlycon(char *buf)
+{
+        if (buf)
+                return 0;
+
+        return early_init_dt_scan_chosen_serial();
+}
+early_param("earlycon", setup_of_earlycon);
+#endif
+
 /**
  * early_init_dt_scan_root - fetch the top level address and size cells
  */