* Bug+Bugfix: Serialdriver 2.6.0-test8(setting custum speed)
@ 2003-10-24 21:19 Heinz-Georg Sawicki
0 siblings, 0 replies; only message in thread
From: Heinz-Georg Sawicki @ 2003-10-24 21:19 UTC (permalink / raw)
To: linux-kernel
Hi!
First excuse me for my bad english.
In case of custom speed the routine uart_get_divisor in serial_core.c
must calcuate the custom baudrate and return it to the caller. It may look
somewhat like this:
unsigned int
uart_get_divisor(struct uart_port *port, unsigned int* pBaud)
{
unsigned int quot;
/*
* Old custom speed handling.
*/
if (*pBaud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST)
{
quot = port->custom_divisor;
*pBaud = port->uartclk / (16 * quot);
}
else
quot = port->uartclk / (16 * (*pBaud));
return quot;
}
This is necessary because serial8250_set_termios in 8250.c uses the
baudrate for setting the fifotriggerlevel
if (baud < 2400)
fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1;
#ifdef CONFIG_SERIAL_8250_RSA
else if (up->port.type == PORT_RSA)
fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_14;
#endif
else
fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_8;
In my case i setup a customdivisor of 11520 to get a baudrate of 10 baud, to
receive the dcf77-signal(UART 16550A, PC-Hardware). Instead of one byte per
second i received 8 bytes at once because of the wrong triggerlevel. By
setting the triggerlevel always to one
:
else
fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1;
i checked that this was the cause for the problem.
By the way, the comment
/*
* Old custom speed handling.
*/
says, that this is the old way for setting up a custom speed. Can you please
tell me the new way for doing this. Thanks.
Have a nice day,
Heinz-Georg Sawicki
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2003-10-24 21:19 Bug+Bugfix: Serialdriver 2.6.0-test8(setting custum speed) Heinz-Georg Sawicki
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