From 03abeac0a222060ae8f02e8359c285df0971437e Mon Sep 17 00:00:00 2001 From: Andrew Victor Date: Thu, 3 May 2007 12:26:24 +0100 Subject: [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 Signed-off-by: Russell King --- drivers/serial/atmel_serial.c | 9 +++++++-- drivers/serial/atmel_serial.h | 3 +++ 2 files changed, 10 insertions(+), 2 deletions(-) (limited to 'drivers') 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) -- cgit v1.2.3