[SERIAL] 8250: set divisor register correctly for AMD Alchemy SoC uart

Alchemy SoC uart have got a non-standard divisor register that needs some
special handling.

This patch adds divisor read/write functions with test and special
handling for Alchemy internal uart.

Signed-off-by: Jon Anders Haugum <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

drivers/serial/8250.c

···
 #define serial_inp(up, offset)		serial_in(up, offset)
 #define serial_outp(up, offset, value)	serial_out(up, offset, value)
 
+/* Uart divisor latch read */
+static inline int _serial_dl_read(struct uart_8250_port *up)
+{
+	return serial_inp(up, UART_DLL) | serial_inp(up, UART_DLM) << 8;
+}
+
+/* Uart divisor latch write */
+static inline void _serial_dl_write(struct uart_8250_port *up, int value)
+{
+	serial_outp(up, UART_DLL, value & 0xff);
+	serial_outp(up, UART_DLM, value >> 8 & 0xff);
+}
+
+#ifdef CONFIG_SERIAL_8250_AU1X00
+/* Au1x00 haven't got a standard divisor latch */
+static int serial_dl_read(struct uart_8250_port *up)
+{
+	if (up->port.iotype == UPIO_AU)
+		return __raw_readl(up->port.membase + 0x28);
+	else
+		return _serial_dl_read(up);
+}
+
+static void serial_dl_write(struct uart_8250_port *up, int value)
+{
+	if (up->port.iotype == UPIO_AU)
+		__raw_writel(value, up->port.membase + 0x28);
+	else
+		_serial_dl_write(up, value);
+}
+#else
+#define serial_dl_read(up) _serial_dl_read(up)
+#define serial_dl_write(up, value) _serial_dl_write(up, value)
+#endif
 
 /*
  * For the 16C950
···
  */
 static int size_fifo(struct uart_8250_port *up)
 {
-	unsigned char old_fcr, old_mcr, old_dll, old_dlm, old_lcr;
+	unsigned char old_fcr, old_mcr, old_lcr;
+	unsigned short old_dl;
 	int count;
 
 	old_lcr = serial_inp(up, UART_LCR);
···
 		    UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
 	serial_outp(up, UART_MCR, UART_MCR_LOOP);
 	serial_outp(up, UART_LCR, UART_LCR_DLAB);
-	old_dll = serial_inp(up, UART_DLL);
-	old_dlm = serial_inp(up, UART_DLM);
-	serial_outp(up, UART_DLL, 0x01);
-	serial_outp(up, UART_DLM, 0x00);
+	old_dl = serial_dl_read(up);
+	serial_dl_write(up, 0x0001);
 	serial_outp(up, UART_LCR, 0x03);
 	for (count = 0; count < 256; count++)
 		serial_outp(up, UART_TX, count);
···
 	serial_outp(up, UART_FCR, old_fcr);
 	serial_outp(up, UART_MCR, old_mcr);
 	serial_outp(up, UART_LCR, UART_LCR_DLAB);
-	serial_outp(up, UART_DLL, old_dll);
-	serial_outp(up, UART_DLM, old_dlm);
+	serial_dl_write(up, old_dl);
 	serial_outp(up, UART_LCR, old_lcr);
 
 	return count;
···
 
 			serial_outp(up, UART_LCR, 0xE0);
 
-			quot = serial_inp(up, UART_DLM) << 8;
-			quot += serial_inp(up, UART_DLL);
+			quot = serial_dl_read(up);
 			quot <<= 3;
 
 			status1 = serial_in(up, 0x04); /* EXCR1 */
···
 			status1 |= 0x10;  /* 1.625 divisor for baud_base --> 921600 */
 			serial_outp(up, 0x04, status1);
 			
-			serial_outp(up, UART_DLL, quot & 0xff);
-			serial_outp(up, UART_DLM, quot >> 8);
+			serial_dl_write(up, quot);
 
 			serial_outp(up, UART_LCR, 0);
 
···
 		serial_outp(up, UART_LCR, cval | UART_LCR_DLAB);/* set DLAB */
 	}
 
-	serial_outp(up, UART_DLL, quot & 0xff);		/* LS of divisor */
-	serial_outp(up, UART_DLM, quot >> 8);		/* MS of divisor */
+	serial_dl_write(up, quot);
 
 	/*
 	 * LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR