Re: [PATCH] 8250.c: Fix to make 16C950 UARTs work

[Russell King <rmk+lkml@arm.linux.org.uk>]

A couple of comments - see below.

On Fri, Sep 09, 2005 at 04:49:27AM +0200, Mathias Adam wrote:
> --- linux-2.6.13-org/drivers/serial/8250.c	2005-08-29 01:41:01.000000000 +0200
> +++ linux-2.6.13/drivers/serial/8250.c	2005-09-09 02:16:49.000000000 +0200
> @@ -1665,7 +1665,7 @@
>  	struct uart_8250_port *up = (struct uart_8250_port *)port;
>  	unsigned char cval, fcr = 0;
>  	unsigned long flags;
> -	unsigned int baud, quot;
> +	unsigned int baud, quot, max_baud;
>  
>  	switch (termios->c_cflag & CSIZE) {
>  	case CS5:
> @@ -1697,9 +1697,28 @@
>  	/*
>  	 * Ask the core to calculate the divisor for us.
>  	 */
> -	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16); 
> +	max_baud = (up->port.type == PORT_16C950 ? port->uartclk/4 : port->uartclk/16);
> +	baud = uart_get_baud_rate(port, termios, old, 0, max_baud); 
>  	quot = serial8250_get_divisor(port, baud);
>  
> +	/* 
> +	 * 16C950 supports additional prescaler ratios between 1:16 and 1:4
> +	 * thus increasing max baud rate to uartclk/4. The following was taken
> +	 * from kernel 2.4 by Mathias Adam <a2@adamis.de> to make the Socket
> +	 * Bluetooth CF Card work under 2.6.13.
> +	 */
> +	if (up->port.type == PORT_16C950) {
> +		unsigned int baud_base = port->uartclk/16;

baud_base appears unused.

> +		if (baud <= port->uartclk/16)
> +			serial_icr_write(up, UART_TCR, 0);
> +		else if (baud <= port->uartclk/8) {
> +			serial_icr_write(up, UART_TCR, 0x8);
> +		} else if (baud <= port->uartclk/4) {
> +			serial_icr_write(up, UART_TCR, 0x4);
> +		} else
> +			serial_icr_write(up, UART_TCR, 0);

baud can't be larger than port->uartclk/4 since you limited it above.

> +	}
> +	
>  	/*
>  	 * Oxford Semi 952 rev B workaround
>  	 */

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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