1 files changed, 22 insertions, 13 deletions

diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c
index 3975df6f7fdb..6611535f4440 100644
--- a/drivers/tty/serial/8250.c
+++ b/drivers/tty/serial/8250.c
@@ -954,6 +954,23 @@ static int broken_efr(struct uart_8250_port *up)
 	return 0;
 }
 
+static inline int ns16550a_goto_highspeed(struct uart_8250_port *up)
+{
+	unsigned char status;
+
+	status = serial_in(up, 0x04); /* EXCR2 */
+#define PRESL(x) ((x) & 0x30)
+	if (PRESL(status) == 0x10) {
+		/* already in high speed mode */
+		return 0;
+	} else {
+		status &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */
+		status |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
+		serial_outp(up, 0x04, status);
+	}
+	return 1;
+}
+
 /*
  * We know that the chip has FIFOs.  Does it have an EFR?  The
  * EFR is located in the same register position as the IIR and
@@ -1025,12 +1042,8 @@ static void autoconfig_16550a(struct uart_8250_port *up)
 			quot = serial_dl_read(up);
 			quot <<= 3;
 
-			status1 = serial_in(up, 0x04); /* EXCR2 */
-			status1 &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */
-			status1 |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
-			serial_outp(up, 0x04, status1);
-
-			serial_dl_write(up, quot);
+			if (ns16550a_goto_highspeed(up))
+				serial_dl_write(up, quot);
 
 			serial_outp(up, UART_LCR, 0);
 
@@ -1616,7 +1629,7 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
 			    up->port.iotype == UPIO_DWAPB32) &&
 			  (iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
 			/* The DesignWare APB UART has an Busy Detect (0x07)
-			 * interrupt meaning an LCR write attempt occured while the
+			 * interrupt meaning an LCR write attempt occurred while the
 			 * UART was busy. The interrupt must be cleared by reading
 			 * the UART status register (USR) and the LCR re-written. */
 			unsigned int status;
@@ -3025,17 +3038,13 @@ void serial8250_resume_port(int line)
 	struct uart_8250_port *up = &serial8250_ports[line];
 
 	if (up->capabilities & UART_NATSEMI) {
-		unsigned char tmp;
-
 		/* Ensure it's still in high speed mode */
 		serial_outp(up, UART_LCR, 0xE0);
 
-		tmp = serial_in(up, 0x04); /* EXCR2 */
-		tmp &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */
-		tmp |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
-		serial_outp(up, 0x04, tmp);
+		ns16550a_goto_highspeed(up);
 
 		serial_outp(up, UART_LCR, 0);
+		up->port.uartclk = 921600*16;
 	}
 	uart_resume_port(&serial8250_reg, &up->port);
 }