2 files changed, 26 insertions, 2 deletions

diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c
index 5644cf2385bb..f67e09da6d33 100644
--- a/drivers/serial/amba-pl011.c
+++ b/drivers/serial/amba-pl011.c
@@ -74,6 +74,7 @@ struct uart_amba_port {
         unsigned int            ifls;           /* vendor-specific */
         unsigned int            lcrh_tx;        /* vendor-specific */
         unsigned int            lcrh_rx;        /* vendor-specific */
+        bool                    oversampling;   /* vendor-specific */
         bool                    autorts;
 };
 
@@ -83,6 +84,7 @@ struct vendor_data {
         unsigned int            fifosize;
         unsigned int            lcrh_tx;
         unsigned int            lcrh_rx;
+        bool                    oversampling;
 };
 
 static struct vendor_data vendor_arm = {
@@ -90,6 +92,7 @@ static struct vendor_data vendor_arm = {
         .fifosize               = 16,
         .lcrh_tx                = UART011_LCRH,
         .lcrh_rx                = UART011_LCRH,
+        .oversampling           = false,
 };
 
 static struct vendor_data vendor_st = {
@@ -97,6 +100,7 @@ static struct vendor_data vendor_st = {
         .fifosize               = 64,
         .lcrh_tx                = ST_UART011_LCRH_TX,
         .lcrh_rx                = ST_UART011_LCRH_RX,
+        .oversampling           = true,
 };
 
 static void pl011_stop_tx(struct uart_port *port)
@@ -499,8 +503,13 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
         /*
          * Ask the core to calculate the divisor for us.
          */
-        baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
-        quot = port->uartclk * 4 / baud;
+        baud = uart_get_baud_rate(port, termios, old, 0,
+                                  port->uartclk/(uap->oversampling ? 8 : 16));
+
+        if (baud > port->uartclk/16)
+                quot = DIV_ROUND_CLOSEST(port->uartclk * 8, baud);
+        else
+                quot = DIV_ROUND_CLOSEST(port->uartclk * 4, baud);
 
         switch (termios->c_cflag & CSIZE) {
         case CS5:
@@ -579,6 +588,13 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
                 uap->autorts = false;
         }
 
+        if (uap->oversampling) {
+                if (baud > port->uartclk/16)
+                        old_cr |= ST_UART011_CR_OVSFACT;
+                else
+                        old_cr &= ~ST_UART011_CR_OVSFACT;
+        }
+
         /* Set baud rate */
         writew(quot & 0x3f, port->membase + UART011_FBRD);
         writew(quot >> 6, port->membase + UART011_IBRD);
@@ -744,6 +760,12 @@ pl011_console_get_options(struct uart_amba_port *uap, int *baud,
                 fbrd = readw(uap->port.membase + UART011_FBRD);
 
                 *baud = uap->port.uartclk * 4 / (64 * ibrd + fbrd);
+
+                if (uap->oversampling) {
+                        if (readw(uap->port.membase + UART011_CR)
+                                  & ST_UART011_CR_OVSFACT)
+                                *baud *= 2;
+                }
         }
 }
 
@@ -839,6 +861,7 @@ static int pl011_probe(struct amba_device *dev, struct amba_id *id)
         uap->ifls = vendor->ifls;
         uap->lcrh_rx = vendor->lcrh_rx;
         uap->lcrh_tx = vendor->lcrh_tx;
+        uap->oversampling = vendor->oversampling;
         uap->port.dev = &dev->dev;
         uap->port.mapbase = dev->res.start;
         uap->port.membase = base;
diff --git a/include/linux/amba/serial.h b/include/linux/amba/serial.h
index 93c96a66c518..e1b634b635f2 100644
--- a/include/linux/amba/serial.h
+++ b/include/linux/amba/serial.h
@@ -86,6 +86,7 @@
 #define UART010_CR_TIE          0x0020
 #define UART010_CR_RIE          0x0010
 #define UART010_CR_MSIE         0x0008
+#define ST_UART011_CR_OVSFACT   0x0008  /* Oversampling factor */
 #define UART01x_CR_IIRLP        0x0004  /* SIR low power mode */
 #define UART01x_CR_SIREN        0x0002  /* SIR enable */
 #define UART01x_CR_UARTEN       0x0001  /* UART enable */