[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>
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 935f48f..3320bcd 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -484,11 +484,16 @@
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) {