1 files changed, 23 insertions, 11 deletions

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index cd1b94a0f451..6fcdb90f616a 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -9,6 +9,7 @@
  * LCR is written whilst busy.  If it is, then a busy detect interrupt is
  * raised, the LCR needs to be rewritten and the uart status register read.
  */
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -119,10 +120,27 @@ static void dw8250_check_lcr(struct uart_port *p, int value)
 	 */
 }
 
+/* Returns once the transmitter is empty or we run out of retries */
+static void dw8250_tx_wait_empty(struct uart_port *p, int tries)
+{
+	unsigned int lsr;
+
+	while (tries--) {
+		lsr = readb (p->membase + (UART_LSR << p->regshift));
+		if (lsr & UART_LSR_TEMT)
+			break;
+		udelay (10);
+	}
+}
+
 static void dw8250_serial_out(struct uart_port *p, int offset, int value)
 {
 	struct dw8250_data *d = p->private_data;
 
+	/* Allow the TX to drain before we reconfigure */
+	if (offset == UART_LCR)
+		dw8250_tx_wait_empty(p, 1000);
+
 	writeb(value, p->membase + (offset << p->regshift));
 
 	if (offset == UART_LCR && !d->uart_16550_compatible)
@@ -339,17 +357,11 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 			p->serial_in = dw8250_serial_in32be;
 			p->serial_out = dw8250_serial_out32be;
 		}
-	} else if (has_acpi_companion(p->dev)) {
-		const struct acpi_device_id *id;
-
-		id = acpi_match_device(p->dev->driver->acpi_match_table,
-				       p->dev);
-		if (id && !strcmp(id->id, "APMC0D08")) {
-			p->iotype = UPIO_MEM32;
-			p->regshift = 2;
-			p->serial_in = dw8250_serial_in32;
-			data->uart_16550_compatible = true;
-		}
+	} else if (acpi_dev_present("APMC0D08", NULL, -1)) {
+		p->iotype = UPIO_MEM32;
+		p->regshift = 2;
+		p->serial_in = dw8250_serial_in32;
+		data->uart_16550_compatible = true;
 	}
 
 	/* Platforms with iDMA */