serial: sh-sci: Clean sci_ports[0] after at earlycon exit

The early_console_setup() function initializes the sci_ports[0].port with
an object of type struct uart_port obtained from the object of type
struct earlycon_device received as argument by the early_console_setup().

It may happen that later, when the rest of the serial ports are probed,
the serial port that was used as earlycon (e.g., port A) to be mapped to a
different position in sci_ports[] and the slot 0 to be used by a different
serial port (e.g., port B), as follows:

sci_ports[0] = port A
sci_ports[X] = port B

In this case, the new port mapped at index zero will have associated data
that was used for earlycon.

In case this happens, after Linux boot, any access to the serial port that
maps on sci_ports[0] (port A) will block the serial port that was used as
earlycon (port B).

To fix this, add early_console_exit() that clean the sci_ports[0] at
earlycon exit time.

Fixes: 0b0cced ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
Cc: [email protected]
Signed-off-by: Claudiu Beznea <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: claudiubeznea

drivers/tty/serial/sh-sci.c

@@ -3535,6 +3535,32 @@ sh_early_platform_init_buffer("earlyprintk", &sci_driver,
 #ifdef CONFIG_SERIAL_SH_SCI_EARLYCON
 static struct plat_sci_port port_cfg __initdata;
 
+static int early_console_exit(struct console *co)
+{
+	struct sci_port *sci_port = &sci_ports[0];
+	struct uart_port *port = &sci_port->port;
+	unsigned long flags;
+	int locked = 1;
+
+	if (port->sysrq)
+		locked = 0;
+	else if (oops_in_progress)
+		locked = uart_port_trylock_irqsave(port, &flags);
+	else
+		uart_port_lock_irqsave(port, &flags);
+
+	/*
+	 * Clean the slot used by earlycon. A new SCI device might
+	 * map to this slot.
+	 */
+	memset(sci_ports, 0, sizeof(*sci_port));
+
+	if (locked)
+		uart_port_unlock_irqrestore(port, flags);
+
+	return 0;
+}
+
 static int __init early_console_setup(struct earlycon_device *device,
 				      int type)
 {
@@ -3551,6 +3577,8 @@ static int __init early_console_setup(struct earlycon_device *device,
 		       SCSCR_RE | SCSCR_TE | port_cfg.scscr);
 
 	device->con->write = serial_console_write;
+	device->con->exit = early_console_exit;
+
 	return 0;
 }
 static int __init sci_early_console_setup(struct earlycon_device *device,