serial: 8250: Add preferred console in serial8250_isa_init_ports()

Prepare 8250 ISA ports to drop kernel command line serial console
handling from console_setup().

We need to set the preferred console in serial8250_isa_init_ports()
to drop a dependency to setup_console() handling the ttyS related
quirks. Otherwise when console_setup() handles the ttyS related
options, console gets enabled only at driver probe time.

Note that this mostly affects x86 as this happens based on define
SERIAL_PORT_DFNS.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20240327110021.59793-7-tony@atomide.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_core.c

@@ -15,6 +15,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/cleanup.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/ioport.h>
@@ -41,6 +42,8 @@
 
 #include <asm/irq.h>
 
+#include "../serial_base.h"	/* For serial_base_add_isa_preferred_console() */
+
 #include "8250.h"
 
 /*
@@ -564,6 +567,8 @@ static void __init serial8250_isa_init_ports(void)
 		port->irqflags |= irqflag;
 		if (serial8250_isa_config != NULL)
 			serial8250_isa_config(i, &up->port, &up->capabilities);
+
+		serial_base_add_isa_preferred_console(serial8250_reg.dev_name, i);
 	}
 }
 

drivers/tty/serial/serial_base.h

@@ -51,6 +51,8 @@ void serial_core_unregister_port(struct uart_driver *drv, struct uart_port *port
 int serial_base_add_preferred_console(struct uart_driver *drv,
 				      struct uart_port *port);
 
+int serial_base_add_isa_preferred_console(const char *name, int idx);
+
 #else
 
 static inline
@@ -60,4 +62,10 @@ int serial_base_add_preferred_console(struct uart_driver *drv,
 	return 0;
 }
 
+static inline
+int serial_base_add_isa_preferred_console(const char *name, int idx)
+{
+	return 0;
+}
+
 #endif

drivers/tty/serial/serial_base_bus.c

@@ -317,6 +317,27 @@ int serial_base_add_preferred_console(struct uart_driver *drv,
 	return serial_base_add_one_prefcon(port_match, drv->dev_name, port->line);
 }
 
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+
+/*
+ * Early ISA ports initialize the console before there is no struct device.
+ * This should be only called from serial8250_isa_init_preferred_console(),
+ * other callers are likely wrong and should rely on earlycon instead.
+ */
+int serial_base_add_isa_preferred_console(const char *name, int idx)
+{
+	return serial_base_add_prefcon(name, idx);
+}
+
+#else
+
+int serial_base_add_isa_preferred_console(const char *name, int idx)
+{
+	return 0;
+}
+
+#endif
+
 #endif
 
 static int serial_base_init(void)