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[PATCH] serial8250: set divisor register correctly for AMD Alchemy SoC u

To: rmk+serial@arm.linux.org.uk
Subject: [PATCH] serial8250: set divisor register correctly for AMD Alchemy SoC uart. 3rd edition.
From: Jon Anders Haugum <jonah@omegav.ntnu.no>
Date: Thu, 20 Apr 2006 14:55:59 +0200 (CEST)
Cc: linux-serial@vger.kernel.org, linux-mips@linux-mips.org
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
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 <jonah@omegav.ntnu.no>

---

3rd edition:
- Removed section covering 16C850 autoconfig.


--- linux-2.6.16-rc5/drivers/serial/8250.c.orig 2006-03-03 02:12:10.000000000 
+0100
+++ linux-2.6.16-rc5/drivers/serial/8250.c      2006-03-03 02:16:19.000000000 
+0100
@@ -362,6 +362,40 @@ serial_out(struct uart_8250_port *up, in
 #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
@@ -494,7 +528,8 @@ static void disable_rsa(struct uart_8250
  */
 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);
@@ -505,10 +540,8 @@ static int size_fifo(struct uart_8250_po
                    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);
@@ -519,8 +552,7 @@ static int size_fifo(struct uart_8250_po
        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;
@@ -750,8 +780,7 @@ static void autoconfig_16550a(struct uar
 
                        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 */
@@ -759,8 +788,7 @@ static void autoconfig_16550a(struct uar
                        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);
 
@@ -1862,8 +1890,7 @@ serial8250_set_termios(struct uart_port 
                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

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