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authorAndrew Victor <andrew@sanpeople.com>2007-05-03 12:26:24 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2007-05-03 14:12:45 +0100
commit03abeac0a222060ae8f02e8359c285df0971437e (patch)
tree96fd9e6f11740a098ffa0958d218ff1f41e4b216 /drivers
parent7c73628f24ea73479232d1b608359aa7d8d2c95d (diff)
[ARM] 4357/1: AT91: Support slower serial baud-rates
Allow slower serial baud-rates by switching the UART clock from MCK to MCK/8. Based on patches by Mike Wolfram and Russell King. Signed-off-by: Andrew Victor <andrew@sanpeople.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/serial/atmel_serial.c9
-rw-r--r--drivers/serial/atmel_serial.h3
2 files changed, 10 insertions, 2 deletions
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 935f48fa501..3320bcd92c0 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -484,11 +484,16 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios * termios,
unsigned long flags;
unsigned int mode, imr, quot, baud;
+ /* Get current mode register */
+ mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL | ATMEL_US_NBSTOP | ATMEL_US_PAR);
+
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
quot = uart_get_divisor(port, baud);
- /* Get current mode register */
- mode = UART_GET_MR(port) & ~(ATMEL_US_CHRL | ATMEL_US_NBSTOP | ATMEL_US_PAR);
+ if (quot > 65535) { /* BRGR is 16-bit, so switch to slower clock */
+ quot /= 8;
+ mode |= ATMEL_US_USCLKS_MCK_DIV8;
+ }
/* byte size */
switch (termios->c_cflag & CSIZE) {
diff --git a/drivers/serial/atmel_serial.h b/drivers/serial/atmel_serial.h
index 11b44360e10..e0141776517 100644
--- a/drivers/serial/atmel_serial.h
+++ b/drivers/serial/atmel_serial.h
@@ -46,6 +46,9 @@
#define ATMEL_US_USMODE_ISO7816_T1 6
#define ATMEL_US_USMODE_IRDA 8
#define ATMEL_US_USCLKS (3 << 4) /* Clock Selection */
+#define ATMEL_US_USCLKS_MCK (0 << 4)
+#define ATMEL_US_USCLKS_MCK_DIV8 (1 << 4)
+#define ATMEL_US_USCLKS_SCK (3 << 4)
#define ATMEL_US_CHRL (3 << 6) /* Character Length */
#define ATMEL_US_CHRL_5 (0 << 6)
#define ATMEL_US_CHRL_6 (1 << 6)