serial: convert early_uart to earlycon for 8250

Beacuse SERIAL_PORT_DFNS is removed from include/asm-i386/serial.h and
include/asm-x86_64/serial.h.  the serial8250_ports need to be probed late in
serial initializing stage.  the console_init=>serial8250_console_init=>
register_console=>serial8250_console_setup will return -ENDEV, and console
ttyS0 can not be enabled at that time.  need to wait till uart_add_one_port in
drivers/serial/serial_core.c to call register_console to get console ttyS0.
that is too late.

Make early_uart to use early_param, so uart console can be used earlier.  Make
it to be bootconsole with CON_BOOT flag, so can use console handover feature.
and it will switch to corresponding normal serial console automatically.

new command line will be:
	console=uart8250,io,0x3f8,9600n8
	console=uart8250,mmio,0xff5e0000,115200n8
or
	earlycon=uart8250,io,0x3f8,9600n8
	earlycon=uart8250,mmio,0xff5e0000,115200n8

it will print in very early stage:
	Early serial console at I/O port 0x3f8 (options '9600n8')
	console [uart0] enabled
later for console it will print:
	console handover: boot [uart0] -> real [ttyS0]

Signed-off-by: <yinghai.lu@sun.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 80 insertions, 79 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index c84dab083a85..0b3ec38ae614 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2514,12 +2514,18 @@ static int __init serial8250_console_setup(struct console *co, char *options)
         return uart_set_options(port, co, baud, parity, bits, flow);
 }
 
+static int __init serial8250_console_early_setup(void)
+{
+        return serial8250_find_port_for_earlycon();
+}
+
 static struct uart_driver serial8250_reg;
 static struct console serial8250_console = {
         .name           = "ttyS",
         .write          = serial8250_console_write,
         .device         = uart_console_device,
         .setup          = serial8250_console_setup,
+        .early_setup    = serial8250_console_early_setup,
         .flags          = CON_PRINTBUFFER,
         .index          = -1,
         .data           = &serial8250_reg,
@@ -2533,7 +2539,7 @@ static int __init serial8250_console_init(void)
 }
 console_initcall(serial8250_console_init);
 
-static int __init find_port(struct uart_port *p)
+int serial8250_find_port(struct uart_port *p)
 {
         int line;
         struct uart_port *port;
@@ -2546,26 +2552,6 @@ static int __init find_port(struct uart_port *p)
         return -ENODEV;
 }
 
-int __init serial8250_start_console(struct uart_port *port, char *options)
-{
-        int line;
-
-        line = find_port(port);
-        if (line < 0)
-                return -ENODEV;
-
-        add_preferred_console("ttyS", line, options);
-        printk("Adding console on ttyS%d at %s 0x%lx (options '%s')\n",
-                line, port->iotype == UPIO_MEM ? "MMIO" : "I/O port",
-                port->iotype == UPIO_MEM ? (unsigned long) port->mapbase :
-                    (unsigned long) port->iobase, options);
-        if (!(serial8250_console.flags & CON_ENABLED)) {
-                serial8250_console.flags &= ~CON_PRINTBUFFER;
-                register_console(&serial8250_console);
-        }
-        return line;
-}
-
 #define SERIAL8250_CONSOLE      &serial8250_console
 #else
 #define SERIAL8250_CONSOLE      NULL
diff --git a/drivers/serial/8250_early.c b/drivers/serial/8250_early.c
index 7e511199b4c5..947c20507e1f 100644
--- a/drivers/serial/8250_early.c
+++ b/drivers/serial/8250_early.c
@@ -17,13 +17,11 @@
  * we locate the device directly by its MMIO or I/O port address.
  *
  * The user can specify the device directly, e.g.,
- *      console=uart,io,0x3f8,9600n8
- *      console=uart,mmio,0xff5e0000,115200n8
- * or platform code can call early_uart_console_init() to set
- * the early UART device.
- *
- * After the normal serial driver starts, we try to locate the
- * matching ttyS device and start a console there.
+ *      earlycon=uart8250,io,0x3f8,9600n8
+ *      earlycon=uart8250,mmio,0xff5e0000,115200n8
+ * or
+ *      console=uart8250,io,0x3f8,9600n8
+ *      console=uart8250,mmio,0xff5e0000,115200n8
  */
 
 #include <linux/tty.h>
@@ -32,17 +30,21 @@
 #include <linux/serial_core.h>
 #include <linux/serial_reg.h>
 #include <linux/serial.h>
+#include <linux/serial_8250.h>
 #include <asm/io.h>
 #include <asm/serial.h>
+#ifdef CONFIG_FIX_EARLYCON_MEM
+#include <asm/pgtable.h>
+#include <asm/fixmap.h>
+#endif
 
-struct early_uart_device {
+struct early_serial8250_device {
         struct uart_port port;
         char options[16];               /* e.g., 115200n8 */
         unsigned int baud;
 };
 
-static struct early_uart_device early_device __initdata;
-static int early_uart_registered __initdata;
+static struct early_serial8250_device early_device;
 
 static unsigned int __init serial_in(struct uart_port *port, int offset)
 {
@@ -80,7 +82,7 @@ static void __init putc(struct uart_port *port, int c)
         serial_out(port, UART_TX, c);
 }
 
-static void __init early_uart_write(struct console *console, const char *s, unsigned int count)
+static void __init early_serial8250_write(struct console *console, const char *s, unsigned int count)
 {
         struct uart_port *port = &early_device.port;
         unsigned int ier;
@@ -111,7 +113,7 @@ static unsigned int __init probe_baud(struct uart_port *port)
         return (port->uartclk / 16) / quot;
 }
 
-static void __init init_port(struct early_uart_device *device)
+static void __init init_port(struct early_serial8250_device *device)
 {
         struct uart_port *port = &device->port;
         unsigned int divisor;
@@ -130,10 +132,9 @@ static void __init init_port(struct early_uart_device *device)
         serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 }
 
-static int __init parse_options(struct early_uart_device *device, char *options)
+static int __init parse_options(struct early_serial8250_device *device, char *options)
 {
         struct uart_port *port = &device->port;
-        int mapsize = 64;
         int mmio, length;
 
         if (!options)
@@ -143,12 +144,18 @@ static int __init parse_options(struct early_uart_device *device, char *options)
         if (!strncmp(options, "mmio,", 5)) {
                 port->iotype = UPIO_MEM;
                 port->mapbase = simple_strtoul(options + 5, &options, 0);
-                port->membase = ioremap(port->mapbase, mapsize);
+#ifdef CONFIG_FIX_EARLYCON_MEM
+                set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, port->mapbase & PAGE_MASK);
+                port->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
+                port->membase += port->mapbase & ~PAGE_MASK;
+#else
+                port->membase = ioremap(port->mapbase, 64);
                 if (!port->membase) {
                         printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n",
                                 __FUNCTION__, port->mapbase);
                         return -ENOMEM;
                 }
+#endif
                 mmio = 1;
         } else if (!strncmp(options, "io,", 3)) {
                 port->iotype = UPIO_PORT;
@@ -175,9 +182,16 @@ static int __init parse_options(struct early_uart_device *device, char *options)
         return 0;
 }
 
-static int __init early_uart_setup(struct console *console, char *options)
+static struct console early_serial8250_console __initdata = {
+        .name   = "uart",
+        .write  = early_serial8250_write,
+        .flags  = CON_PRINTBUFFER | CON_BOOT,
+        .index  = -1,
+};
+
+static int __init early_serial8250_setup(char *options)
 {
-        struct early_uart_device *device = &early_device;
+        struct early_serial8250_device *device = &early_device;
         int err;
 
         if (device->port.membase || device->port.iobase)
@@ -190,61 +204,48 @@ static int __init early_uart_setup(struct console *console, char *options)
         return 0;
 }
 
-static struct console early_uart_console __initdata = {
-        .name   = "uart",
-        .write  = early_uart_write,
-        .setup  = early_uart_setup,
-        .flags  = CON_PRINTBUFFER,
-        .index  = -1,
-};
-
-static int __init early_uart_console_init(void)
-{
-        if (!early_uart_registered) {
-                register_console(&early_uart_console);
-                early_uart_registered = 1;
-        }
-        return 0;
-}
-console_initcall(early_uart_console_init);
-
-int __init early_serial_console_init(char *cmdline)
+int __init setup_early_serial8250_console(char *cmdline)
 {
         char *options;
         int err;
 
-        options = strstr(cmdline, "console=uart,");
-        if (!options)
-                return -ENODEV;
+        options = strstr(cmdline, "uart8250,");
+        if (!options) {
+                options = strstr(cmdline, "uart,");
+                if (!options)
+                        return 0;
+        }
 
         options = strchr(cmdline, ',') + 1;
-        if ((err = early_uart_setup(NULL, options)) < 0)
+        if ((err = early_serial8250_setup(options)) < 0)
                 return err;
-        return early_uart_console_init();
+
+        register_console(&early_serial8250_console);
+
+        return 0;
 }
 
-static int __init early_uart_console_switch(void)
+int __init serial8250_find_port_for_earlycon(void)
 {
-        struct early_uart_device *device = &early_device;
+        struct early_serial8250_device *device = &early_device;
         struct uart_port *port = &device->port;
-        int mmio, line;
+        int line;
+        int ret;
 
-        if (!(early_uart_console.flags & CON_ENABLED))
-                return 0;
+        if (!device->port.membase && !device->port.iobase)
+                return -ENODEV;
 
-        /* Try to start the normal driver on a matching line.  */
-        mmio = (port->iotype == UPIO_MEM);
-        line = serial8250_start_console(port, device->options);
+        line = serial8250_find_port(port);
         if (line < 0)
-                printk("No ttyS device at %s 0x%lx for console\n",
-                        mmio ? "MMIO" : "I/O port",
-                        mmio ? port->mapbase :
-                            (unsigned long) port->iobase);
+                return -ENODEV;
 
-        unregister_console(&early_uart_console);
-        if (mmio)
-                iounmap(port->membase);
+        ret = update_console_cmdline("uart", 8250,
+                             "ttyS", line, device->options);
+        if (ret < 0)
+                ret = update_console_cmdline("uart", 0,
+                                     "ttyS", line, device->options);
 
-        return 0;
+        return ret;
 }
-late_initcall(early_uart_console_switch);
+
+early_param("earlycon", setup_early_serial8250_console);
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 2adbed4e10f3..cab42cbd920d 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -62,8 +62,22 @@ config SERIAL_8250_CONSOLE
           kernel will automatically use the first serial line, /dev/ttyS0, as
           system console.
 
+          you can set that using a kernel command line option such as
+          "console=uart8250,io,0x3f8,9600n8"
+          "console=uart8250,mmio,0xff5e0000,115200n8".
+          and it will switch to normal serial console when correponding port is
+          ready.
+          "earlycon=uart8250,io,0x3f8,9600n8"
+          "earlycon=uart8250,mmio,0xff5e0000,115200n8".
+          it will not only setup early console.
+
           If unsure, say N.
 
+config FIX_EARLYCON_MEM
+        bool
+        depends on X86
+        default y
+
 config SERIAL_8250_GSC
         tristate
         depends on SERIAL_8250 && GSC