diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index b5def356af63b70e3ebc2e23a48da0753e41b47e..3db9d6e19660da4a89042e8a26113de8d9da5bfa 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -497,6 +497,11 @@ static void univ8250_rsa_support(struct uart_ops *ops)
 #define univ8250_rsa_support(x)		do { } while (0)
 #endif /* CONFIG_SERIAL_8250_RSA */
 
+static inline void serial8250_apply_quirks(struct uart_8250_port *up)
+{
+	up->port.quirks |= skip_txen_test ? UPQ_NO_TXEN_TEST : 0;
+}
+
 static void __init serial8250_isa_init_ports(void)
 {
 	struct uart_8250_port *up;
@@ -577,9 +582,7 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev)
 
 		up->port.dev = dev;
 
-		if (skip_txen_test)
-			up->port.flags |= UPF_NO_TXEN_TEST;
-
+		serial8250_apply_quirks(up);
 		uart_add_one_port(drv, &up->port);
 	}
 }
@@ -1006,9 +1009,6 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 		if (up->port.dev)
 			uart->port.dev = up->port.dev;
 
-		if (skip_txen_test)
-			uart->port.flags |= UPF_NO_TXEN_TEST;
-
 		if (up->port.flags & UPF_FIXED_TYPE)
 			uart->port.type = up->port.type;
 
@@ -1047,6 +1047,7 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 			serial8250_isa_config(0, &uart->port,
 					&uart->capabilities);
 
+		serial8250_apply_quirks(uart);
 		ret = uart_add_one_port(&serial8250_reg, &uart->port);
 		if (ret == 0)
 			ret = uart->port.line;
@@ -1081,11 +1082,10 @@ void serial8250_unregister_port(int line)
 	uart_remove_one_port(&serial8250_reg, &uart->port);
 	if (serial8250_isa_devs) {
 		uart->port.flags &= ~UPF_BOOT_AUTOCONF;
-		if (skip_txen_test)
-			uart->port.flags |= UPF_NO_TXEN_TEST;
 		uart->port.type = PORT_UNKNOWN;
 		uart->port.dev = &serial8250_isa_devs->dev;
 		uart->capabilities = 0;
+		serial8250_apply_quirks(uart);
 		uart_add_one_port(&serial8250_reg, &uart->port);
 	} else {
 		uart->port.dev = NULL;
diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 553823c12c2fb395e674dc06243db05718791e5e..e82d7d521010b3a4fd5d272e8f5b46da1c983a3b 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1548,7 +1548,7 @@ static int skip_tx_en_setup(struct serial_private *priv,
 			const struct pciserial_board *board,
 			struct uart_8250_port *port, int idx)
 {
-	port->port.flags |= UPF_NO_TXEN_TEST;
+	port->port.quirks |= UPQ_NO_TXEN_TEST;
 	dev_dbg(&priv->dev->dev,
 		"serial8250: skipping TxEn test for device [%04x:%04x] subsystem [%04x:%04x]\n",
 		priv->dev->vendor, priv->dev->device,
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index a5fe0e66c60725bf227ea8acf2e93fe2adda5c4c..25aae660cb9e2821664e806399908f388565c82f 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2304,7 +2304,7 @@ int serial8250_do_startup(struct uart_port *port)
 	 * test if we receive TX irq.  This way, we'll never enable
 	 * UART_BUG_TXEN.
 	 */
-	if (up->port.flags & UPF_NO_TXEN_TEST)
+	if (up->port.quirks & UPQ_NO_TXEN_TEST)
 		goto dont_test_tx_en;
 
 	/*
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 1775500294bb3bab35087cca19def9fc9df2a717..8dc24c855a70b96841e8a646a16ad7c6edeff9e1 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -20,7 +20,7 @@
 #ifndef LINUX_SERIAL_CORE_H
 #define LINUX_SERIAL_CORE_H
 
-
+#include <linux/bitops.h>
 #include <linux/compiler.h>
 #include <linux/interrupt.h>
 #include <linux/circ_buf.h>
@@ -144,7 +144,7 @@ struct uart_port {
 	unsigned char		x_char;			/* xon/xoff char */
 	unsigned char		regshift;		/* reg offset shift */
 	unsigned char		iotype;			/* io access style */
-	unsigned char		unused1;
+	unsigned char		quirks;			/* internal quirks */
 
 #define UPIO_PORT		(SERIAL_IO_PORT)	/* 8b I/O port access */
 #define UPIO_HUB6		(SERIAL_IO_HUB6)	/* Hub6 ISA card */
@@ -155,6 +155,9 @@ struct uart_port {
 #define UPIO_MEM32BE		(SERIAL_IO_MEM32BE)	/* 32b big endian */
 #define UPIO_MEM16		(SERIAL_IO_MEM16)	/* 16b little endian */
 
+	/* quirks must be updated while holding port mutex */
+#define UPQ_NO_TXEN_TEST	BIT(0)
+
 	unsigned int		read_status_mask;	/* driver specific */
 	unsigned int		ignore_status_mask;	/* driver specific */
 	struct uart_state	*state;			/* pointer to parent state */
@@ -175,7 +178,6 @@ struct uart_port {
 	 * [for bit definitions in the UPF_CHANGE_MASK]
 	 *
 	 * Bits [0..UPF_LAST_USER] are userspace defined/visible/changeable
-	 * except bit 15 (UPF_NO_TXEN_TEST) which is masked off.
 	 * The remaining bits are serial-core specific and not modifiable by
 	 * userspace.
 	 */
@@ -192,7 +194,6 @@ struct uart_port {
 #define UPF_SPD_SHI		((__force upf_t) ASYNC_SPD_SHI        /* 12 */ )
 #define UPF_LOW_LATENCY		((__force upf_t) ASYNC_LOW_LATENCY    /* 13 */ )
 #define UPF_BUGGY_UART		((__force upf_t) ASYNC_BUGGY_UART     /* 14 */ )
-#define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))
 #define UPF_MAGIC_MULTIPLIER	((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )
 
 #define UPF_NO_THRE_TEST	((__force upf_t) (1 << 19))