[PATCH v1 2/2] serial: 8250: Explicitly show we initialise ISA ports only once

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

serial8250_isa_init_ports() uses home grown approach to make itself
a singleton. Instead, explicitly show that we initialise ISA ports
once by providing a helper function which calls the original function
via DO_ONCE() macro.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_core.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index cae61d1ebec5..9c0d6693f745 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -22,6 +22,7 @@
 #include <linux/console.h>
 #include <linux/sysrq.h>
 #include <linux/delay.h>
+#include <linux/once.h>
 #include <linux/platform_device.h>
 #include <linux/tty.h>
 #include <linux/ratelimit.h>
@@ -495,13 +496,8 @@ static inline void serial8250_apply_quirks(struct uart_8250_port *up)
 static void __init serial8250_isa_init_ports(void)
 {
 	struct uart_8250_port *up;
-	static int first = 1;
 	int i, irqflag = 0;
 
-	if (!first)
-		return;
-	first = 0;
-
 	if (nr_uarts > UART_NR)
 		nr_uarts = UART_NR;
 
@@ -555,6 +551,11 @@ static void __init serial8250_isa_init_ports(void)
 	}
 }
 
+static void __init serial8250_isa_init_ports_once(void)
+{
+	DO_ONCE(serial8250_isa_init_ports);
+}
+
 static void __init
 serial8250_register_ports(struct uart_driver *drv, struct device *dev)
 {
@@ -686,7 +687,7 @@ static int __init univ8250_console_init(void)
 	if (nr_uarts == 0)
 		return -ENODEV;
 
-	serial8250_isa_init_ports();
+	serial8250_isa_init_ports_once();
 	register_console(&univ8250_console);
 	return 0;
 }
@@ -719,7 +720,7 @@ int __init early_serial_setup(struct uart_port *port)
 	if (port->line >= ARRAY_SIZE(serial8250_ports) || nr_uarts == 0)
 		return -ENODEV;
 
-	serial8250_isa_init_ports();
+	serial8250_isa_init_ports_once();
 	p = &serial8250_ports[port->line].port;
 	p->iobase       = port->iobase;
 	p->membase      = port->membase;
@@ -1170,7 +1171,7 @@ static int __init serial8250_init(void)
 	if (nr_uarts == 0)
 		return -ENODEV;
 
-	serial8250_isa_init_ports();
+	serial8250_isa_init_ports_once();
 
 	pr_info("Serial: 8250/16550 driver, %d ports, IRQ sharing %sabled\n",
 		nr_uarts, share_irqs ? "en" : "dis");
-- 
2.27.0