From: Mathias Adam <a2@adamis.de>
To: linux-kernel@vger.kernel.org
Cc: rmk+serial@arm.linux.org.uk
Subject: Re: [PATCH] 8250.c: Fix to make 16C950 UARTs work
Date: Fri, 9 Sep 2005 04:49:27 +0200 [thread overview]
Message-ID: <20050909024926.GA13643@adamis.de> (raw)
In-Reply-To: <4320EC45.1080108@stesmi.com>
Stefan Smietanowski wrote:
> Mathias Adam wrote:
> > 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.
> > - unsigned int baud, quot;
> > + unsigned int baud, quot, max_baud;
> ^^^^^^^^
> > - 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);
> ^^^^^^^^
>
> Did you even compile test this?
Oops, I really really wonder how THIS could have happened as I just attached
my existing patch file (which was and still is correct) without touching
it - at least that's what I thought... Sorry!
Mathias Adam
I hope everything's alright this time:
--- 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;
+ 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
*/
next prev parent reply other threads:[~2005-09-09 2:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-09 1:31 [PATCH] 8250.c: Fix to make 16C950 UARTs work Mathias Adam
2005-09-09 1:58 ` Stefan Smietanowski
2005-09-09 2:49 ` Mathias Adam [this message]
2005-09-09 10:18 ` Russell King
2005-09-09 14:42 ` Mathias Adam
2005-09-16 12:11 ` Mathias Adam
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20050909024926.GA13643@adamis.de \
--to=a2@adamis.de \
--cc=linux-kernel@vger.kernel.org \
--cc=rmk+serial@arm.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox