Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965224AbVIIBb0 (ORCPT ); Thu, 8 Sep 2005 21:31:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965227AbVIIBb0 (ORCPT ); Thu, 8 Sep 2005 21:31:26 -0400 Received: from smtp01.gra.de ([62.146.73.187]:18654 "EHLO minne.gra.de") by vger.kernel.org with ESMTP id S965224AbVIIBb0 (ORCPT ); Thu, 8 Sep 2005 21:31:26 -0400 Date: Fri, 9 Sep 2005 03:31:45 +0200 From: Mathias Adam To: linux-kernel@vger.kernel.org Cc: rmk+serial@arm.linux.org.uk Subject: [PATCH] 8250.c: Fix to make 16C950 UARTs work Message-ID: <20050909013144.GA6660@adamis.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2331 Lines: 63 Currently serial8250_set_termios() refuses to program a baud rate larger than uartclk/16. However the 16C950 supports baud rates up to uartclk/4. This worked already with Linux 2.4 so the biggest part of this patch was simply taken from there and adapted to 2.6. I needed this to get a Socket Bluetooth CF Card to work with BlueZ under 2.6 (the card did work under 2.4 already). I posted the patch a while ago on the BlueZ mailing list and got reports that it works as it should for a number of people so one could consider including it into the standard kernel - opinions? Please CC me as I'm not subscribed to the list. Mathias Adam --- 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 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; + 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); + } + /* * Oxford Semi 952 rev B workaround */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/