[ARM] S3C: Add UDIVSLOT support for newer UARTS

Add support for the UDIVSLOT register on the newer UART blocks
which gives the capability of 1/16ths adjustment to the baud rate.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>

diff --git a/drivers/serial/s3c6400.c b/drivers/serial/s3c6400.c
index 06936d1..3e37852 100644 (file)
--- a/drivers/serial/s3c6400.c
+++ b/drivers/serial/s3c6400.c
@@ -102,6 +102,7 @@ static struct s3c24xx_uart_info s3c6400_uart_inf = {
        .name           = "Samsung S3C6400 UART",
        .type           = PORT_S3C6400,
        .fifosize       = 64,
+       .has_divslot    = 1,
        .rx_fifomask    = S3C2440_UFSTAT_RXMASK,
        .rx_fifoshift   = S3C2440_UFSTAT_RXSHIFT,
        .rx_fifofull    = S3C2440_UFSTAT_RXFULL,

diff --git a/drivers/serial/samsung.c b/drivers/serial/samsung.c
index e06686a..93b5d75 100644 (file)
--- a/drivers/serial/samsung.c
+++ b/drivers/serial/samsung.c
@@ -508,6 +508,7 @@ s3c24xx_serial_setsource(struct uart_port *port, struct s3c24xx_uart_clksrc *c)
 struct baud_calc {
        struct s3c24xx_uart_clksrc      *clksrc;
        unsigned int                     calc;
+       unsigned int                     divslot;
        unsigned int                     quot;
        struct clk                      *src;
 };
@@ -517,6 +518,7 @@ static int s3c24xx_serial_calcbaud(struct baud_calc *calc,
                                   struct s3c24xx_uart_clksrc *clksrc,
                                   unsigned int baud)
 {
+       struct s3c24xx_uart_port *ourport = to_ourport(port);
        unsigned long rate;
 
        calc->src = clk_get(port->dev, clksrc->name);
@@ -527,8 +529,24 @@ static int s3c24xx_serial_calcbaud(struct baud_calc *calc,
        rate /= clksrc->divisor;
 
        calc->clksrc = clksrc;
-       calc->quot = (rate + (8 * baud)) / (16 * baud);
-       calc->calc = (rate / (calc->quot * 16));
+
+       if (ourport->info->has_divslot) {
+               unsigned long div = rate / baud;
+
+               /* The UDIVSLOT register on the newer UARTs allows us to
+                * get a divisor adjustment of 1/16th on the baud clock.
+                *
+                * We don't keep the UDIVSLOT value (the 16ths we calculated
+                * by not multiplying the baud by 16) as it is easy enough
+                * to recalculate.
+                */
+
+               calc->quot = div / 16;
+               calc->calc = rate / div;
+       } else {
+               calc->quot = (rate + (8 * baud)) / (16 * baud);
+               calc->calc = (rate / (calc->quot * 16));
+       }
 
        calc->quot--;
        return 1;
@@ -611,6 +629,30 @@ static unsigned int s3c24xx_serial_getclk(struct uart_port *port,
        return best->quot;
 }
 
+/* udivslot_table[]
+ *
+ * This table takes the fractional value of the baud divisor and gives
+ * the recommended setting for the UDIVSLOT register.
+ */
+static u16 udivslot_table[16] = {
+       [0] = 0x0000,
+       [1] = 0x0080,
+       [2] = 0x0808,
+       [3] = 0x0888,
+       [4] = 0x2222,
+       [5] = 0x4924,
+       [6] = 0x4A52,
+       [7] = 0x54AA,
+       [8] = 0x5555,
+       [9] = 0xD555,
+       [10] = 0xD5D5,
+       [11] = 0xDDD5,
+       [12] = 0xDDDD,
+       [13] = 0xDFDD,
+       [14] = 0xDFDF,
+       [15] = 0xFFDF,
+};
+
 static void s3c24xx_serial_set_termios(struct uart_port *port,
                                       struct ktermios *termios,
                                       struct ktermios *old)
@@ -623,6 +665,7 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
        unsigned int baud, quot;
        unsigned int ulcon;
        unsigned int umcon;
+       unsigned int udivslot = 0;
 
        /*
         * We don't support modem control lines.
@@ -644,6 +687,7 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
        /* check to see if we need  to change clock source */
 
        if (ourport->clksrc != clksrc || ourport->baudclk != clk) {
+               dbg("selecting clock %p\n", clk);
                s3c24xx_serial_setsource(port, clksrc);
 
                if (ourport->baudclk != NULL && !IS_ERR(ourport->baudclk)) {
@@ -658,6 +702,13 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
                ourport->baudclk_rate = clk ? clk_get_rate(clk) : 0;
        }
 
+       if (ourport->info->has_divslot) {
+               unsigned int div = ourport->baudclk_rate / baud;
+
+               udivslot = udivslot_table[div & 15];
+               dbg("udivslot = %04x (div %d)\n", udivslot, div & 15);
+       }
+
        switch (termios->c_cflag & CSIZE) {
        case CS5:
                dbg("config: 5bits/char\n");
@@ -697,12 +748,16 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 
        spin_lock_irqsave(&port->lock, flags);
 
-       dbg("setting ulcon to %08x, brddiv to %d\n", ulcon, quot);
+       dbg("setting ulcon to %08x, brddiv to %d, udivslot %08x\n",
+           ulcon, quot, udivslot);
 
        wr_regl(port, S3C2410_ULCON, ulcon);
        wr_regl(port, S3C2410_UBRDIV, quot);
        wr_regl(port, S3C2410_UMCON, umcon);
 
+       if (ourport->info->has_divslot)
+               wr_regl(port, S3C2443_DIVSLOT, udivslot);
+
        dbg("uart: ulcon = 0x%08x, ucon = 0x%08x, ufcon = 0x%08x\n",
            rd_regl(port, S3C2410_ULCON),
            rd_regl(port, S3C2410_UCON),

diff --git a/drivers/serial/samsung.h b/drivers/serial/samsung.h
index 571d6b9..7afb948 100644 (file)
--- a/drivers/serial/samsung.h
+++ b/drivers/serial/samsung.h
@@ -21,6 +21,10 @@ struct s3c24xx_uart_info {
        unsigned long           tx_fifoshift;
        unsigned long           tx_fifofull;
 
+       /* uart port features */
+
+       unsigned int            has_divslot:1;
+
        /* clock source control */
 
        int (*get_clksrc)(struct uart_port *, struct s3c24xx_uart_clksrc *clk);