8250: FIX Fourth port offset of Pericom PI7C9X7954 boards

Hi,
below patch to fix Fourth port offset of Percom PI7C9X7954 boards.

I had a problem using Fourth port on a pci express serial board based on Pericom
PI7C9X7954. Reading datasheet I notice a "special" offset assign to this port
when used in I/O mode.

Offset 0x0 ->  UART 0
Offset 0x8 ->  UART 1
Offset 0x10 ->  UART 2
Offset 0x38 ->  UART 3  <<---- This don't follow a logical sequence

This patch add a different init to last port, to have right offset.

I check also Pericom 7952 and 7958 but that devices follow logical sequence,
so they are ok.

Regards,
Angelo
Signed-off-by: Angelo Butti <buttiangelo@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_pci.c

@@ -1329,6 +1329,30 @@ static int pci_default_setup(struct serial_private *priv,
 	return setup_port(priv, port, bar, offset, board->reg_shift);
 }
 
+static int pci_pericom_setup(struct serial_private *priv,
+		  const struct pciserial_board *board,
+		  struct uart_8250_port *port, int idx)
+{
+	unsigned int bar, offset = board->first_offset, maxnr;
+
+	bar = FL_GET_BASE(board->flags);
+	if (board->flags & FL_BASE_BARS)
+		bar += idx;
+	else
+		offset += idx * board->uart_offset;
+
+	if (idx==3)
+		offset = 0x38;
+
+	maxnr = (pci_resource_len(priv->dev, bar) - board->first_offset) >>
+		(board->reg_shift + 3);
+
+	if (board->flags & FL_REGION_SZ_CAP && idx >= maxnr)
+		return 1;
+
+	return setup_port(priv, port, bar, offset, board->reg_shift);
+}
+
 static int
 ce4100_serial_setup(struct serial_private *priv,
 		  const struct pciserial_board *board,
@@ -2095,6 +2119,16 @@ static struct pci_serial_quirk pci_serial_quirks[] __refdata = {
 		.setup		= pci_default_setup,
 		.exit		= pci_plx9050_exit,
 	},
+	/*
+	 * Pericom (Only 7954 - It have a offset jump for port 4)
+	 */
+	{
+		.vendor		= PCI_VENDOR_ID_PERICOM,
+		.device		= PCI_DEVICE_ID_PERICOM_PI7C9X7954,
+		.subvendor	= PCI_ANY_ID,
+		.subdevice	= PCI_ANY_ID,
+		.setup		= pci_pericom_setup,
+	},
 	/*
 	 * PLX
 	 */