of/serial: move earlycon early_param handling to serial

BugLink: https://bugs.launchpad.net/bugs/1744754

We have multiple "earlycon" early_param handlers - merge the DT one into
the main earlycon one.  It's a cleanup that also will be useful
to defer setting up DT console until ACPI/DT decision is made.

Rename the exported function to avoid clashing with the function from
arch/microblaze/kernel/prom.c
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Tested-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit d503187b)
[ dannf: Add missing #include <linux/of_fdt.h> ]
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/of/fdt.c

@@ -801,7 +801,7 @@ static inline void early_init_dt_check_for_initrd(unsigned long node)
 #ifdef CONFIG_SERIAL_EARLYCON
 extern struct of_device_id __earlycon_of_table[];
 
-static int __init early_init_dt_scan_chosen_serial(void)
+int __init early_init_dt_scan_chosen_stdout(void)
 {
 	int offset;
 	const char *p;
@@ -846,15 +846,6 @@ static int __init early_init_dt_scan_chosen_serial(void)
 	}
 	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
 
 /**

drivers/tty/serial/earlycon.c

@@ -20,6 +20,7 @@
 #include <linux/serial_core.h>
 #include <linux/sizes.h>
 #include <linux/mod_devicetable.h>
+#include <linux/of_fdt.h>
 
 #ifdef CONFIG_FIX_EARLYCON_MEM
 #include <asm/fixmap.h>
@@ -188,7 +189,7 @@ static int __init param_setup_earlycon(char *buf)
 	 * don't generate a warning from parse_early_params() in that case
 	 */
 	if (!buf || !buf[0])
-		return 0;
+		return early_init_dt_scan_chosen_stdout();
 
 	err = setup_earlycon(buf);
 	if (err == -ENOENT || err == -EALREADY)

include/linux/of_fdt.h

@@ -14,6 +14,7 @@
 
 #include <linux/types.h>
 #include <linux/init.h>
+#include <linux/errno.h>
 
 /* Definitions used by the flattened device tree */
 #define OF_DT_HEADER		0xd00dfeed	/* marker */
@@ -63,6 +64,7 @@ extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data);
 extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
 				     int depth, void *data);
+extern int early_init_dt_scan_chosen_stdout(void);
 extern void early_init_fdt_scan_reserved_mem(void);
 extern void early_init_fdt_reserve_self(void);
 extern void early_init_dt_add_memory_arch(u64 base, u64 size);
@@ -91,6 +93,7 @@ extern void early_get_first_memblock_info(void *, phys_addr_t *);
 extern u64 fdt_translate_address(const void *blob, int node_offset);
 extern void of_fdt_limit_memory(int limit);
 #else /* CONFIG_OF_FLATTREE */
+static inline int early_init_dt_scan_chosen_stdout(void) { return -ENODEV; }
 static inline void early_init_fdt_scan_reserved_mem(void) {}
 static inline void early_init_fdt_reserve_self(void) {}
 static inline const char *of_flat_dt_get_machine_name(void) { return NULL; }