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[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>
This commit is contained in:
Andrew Victor 2007-05-03 12:26:24 +01:00 committed by Russell King
parent 7c73628f24
commit 03abeac0a2
2 changed files with 10 additions and 2 deletions
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9
drivers/serial/atmel_serial.c
View File

@ -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) {

3
drivers/serial/atmel_serial.h
View File

@ -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)