Re: [patch] early printk and boot console fixups.

["Yinghai Lu" <yhlu.kernel@gmail.com>]

On 5/17/07, Maciej W. Rozycki <macro@linux-mips.org> wrote:
> On Wed, 16 May 2007, Bjorn Helgaas wrote:
>
> > >  Given the generic name of "uart" I am assuming this will work with any
> > > UART driver making use of the serial_core.c core -- am I correct?
> >
> > I knew somebody would ask that eventually :-)
> >
> > Unfortunately, the answer is "no."  "console=uart" only works with
> > 8250-compatible devices.
>
>  But is it a design limitation or is it just that other UART drivers have
> to be modified to work with this option?  My point is if the former, then
> the option should be something like "console=8250" (the right-hand side
> being the name of the driver involved; others may want to add support for
> other drivers).  If the latter, then it's fine as is as other UART drivers
> may be wired to this code as a need arises.
>
>   Maciej
Actually that early_uart is not real early one.
it is called via console_initcall.

for IA64, Bjom is calling that directly in setup_arch.

Please check my patch to make it to be called via early_param, that
will be good to other platform.

also you may extend to support other early_uart.

YH

[PATCH] serial: make early_uart to use early_prarm instead of console_initcall

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.
new command line will be
earlycon=uart,io,0x3f8,9600n8 console=ttyS0,9600
it will print in very early stage
Early serial console at I/O port 0x3f8 (options '9600n8')
later for console it will print
console handover: boot [uart0] -> real [ttyS0]

Signed-off-by: <yinghai.lu@sun.com>

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 48e259a..2a76618 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2533,39 +2538,6 @@ static int __init serial8250_console_init(void)
 }
 console_initcall(serial8250_console_init);
 
-static int __init find_port(struct uart_port *p)
-{
-	int line;
-	struct uart_port *port;
-
-	for (line = 0; line < nr_uarts; line++) {
-		port = &serial8250_ports[line].port;
-		if (uart_match_port(p, port))
-			return line;
-	}
-	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 7e51119..f320f8f 100644
--- a/drivers/serial/8250_early.c
+++ b/drivers/serial/8250_early.c
@@ -17,13 +17,9 @@
  * 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.
+ *	earlycon=uart,io,0x3f8,9600n8
+ *	earlycon=uart,mmio,0xff5e0000,115200n8
  *
- * After the normal serial driver starts, we try to locate the
- * matching ttyS device and start a console there.
  */
 
 #include <linux/tty.h>
@@ -42,7 +38,6 @@ struct early_uart_device {
 };
 
 static struct early_uart_device early_device __initdata;
-static int early_uart_registered __initdata;
 
 static unsigned int __init serial_in(struct uart_port *port, int offset)
 {
@@ -175,6 +170,13 @@ static int __init parse_options(struct early_uart_device *device, char *options)
 	return 0;
 }
 
+static struct console early_uart_console __initdata = {
+	.name	= "uart",
+	.write	= early_uart_write,
+	.flags	= CON_PRINTBUFFER,
+	.index	= -1,
+};
+
 static int __init early_uart_setup(struct console *console, char *options)
 {
 	struct early_uart_device *device = &early_device;
@@ -190,61 +192,41 @@ 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)
+static int __init setup_early_serial_console(char *cmdline)
 {
 	char *options;
 	int err;
 
-	options = strstr(cmdline, "console=uart,");
+	options = strstr(cmdline, "uart,");
 	if (!options)
 		return -ENODEV;
 
 	options = strchr(cmdline, ',') + 1;
 	if ((err = early_uart_setup(NULL, options)) < 0)
 		return err;
-	return early_uart_console_init();
+
+	register_console(&early_uart_console);
+	early_uart_console.flags |= CON_BOOT;
+	return 0;
 }
 
-static int __init early_uart_console_switch(void)
+early_param("earlycon", setup_early_serial_console);
+
+static int __init early_uart_console_post(void)
 {
 	struct early_uart_device *device = &early_device;
 	struct uart_port *port = &device->port;
-	int mmio, line;
+	int mmio;
 
 	if (!(early_uart_console.flags & CON_ENABLED))
 		return 0;
 
-	/* Try to start the normal driver on a matching line.  */
 	mmio = (port->iotype == UPIO_MEM);
-	line = serial8250_start_console(port, device->options);
-	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);
-
-	unregister_console(&early_uart_console);
+
 	if (mmio)
 		iounmap(port->membase);
 
 	return 0;
 }
-late_initcall(early_uart_console_switch);
+
+late_initcall(early_uart_console_post);
diff --git a/include/linux/serial.h b/include/linux/serial.h
index 33fc8cb..deb7143 100644
--- a/include/linux/serial.h
+++ b/include/linux/serial.h
@@ -177,11 +177,5 @@ struct serial_icounter_struct {
 #ifdef __KERNEL__
 #include <linux/compiler.h>
 
-/* Allow architectures to override entries in serial8250_ports[] at run time: */
-struct uart_port;	/* forward declaration */
-extern int early_serial_setup(struct uart_port *port);
-extern int early_serial_console_init(char *options);
-extern int serial8250_start_console(struct uart_port *port, char *options);
-
 #endif /* __KERNEL__ */
 #endif /* _LINUX_SERIAL_H */