[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
--- a/drivers/serial/s3c6400.c
+++ b/drivers/serial/s3c6400.c
@@ -102,6 +102,7 @@
.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
--- a/drivers/serial/samsung.c
+++ b/drivers/serial/samsung.c
@@ -508,6 +508,7 @@
struct baud_calc {
struct s3c24xx_uart_clksrc *clksrc;
unsigned int calc;
+ unsigned int divslot;
unsigned int quot;
struct clk *src;
};
@@ -517,6 +518,7 @@
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 @@
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 @@
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 @@
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 @@
/* 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 @@
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 @@
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
--- a/drivers/serial/samsung.h
+++ b/drivers/serial/samsung.h
@@ -21,6 +21,10 @@
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);