adulau/aha
1
0
Fork 0
mirror of https://github.com/adulau/aha.git synced 2024-12-28 11:46:19 +00:00
Code Issues Projects Releases Packages Wiki Activity

8250: Now honours baud rate lower bounds

Browse source 
A platform clock drives 8250 ports in most SOC systems, the clock
might run at high frequencies, and so it's not always possible to
downscale uart clock to a desired value.

Currently the 8250 uart driver accepts not supported baud rates, and
what is worse, it is doing this silently, and then passes not accepted
values to a new termios, so userspace has no chance to catch this kind
of errors (userspace verifies that settings were accepted by reading
back and comparing the settings).

This patch fixes the issue by passing minimum baud rate to the
uart_get_baud_rate() call, the call should take care of all bounds,
so userspace should now report:

  # stty -F /dev/ttyS0 speed 300
  115200
  stty: /dev/ttyS0: unable to perform all requested operations

p.s. uart_get_baud_rate() falls back to 9600, which still might be too
     low for some 10 GHz platforms, but that's a separate issue, and
     we can wait with fixing this till we find such a platform.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Anton Vorontsov 2009-09-19 13:13:20 -07:00 committed by Live-CD User
parent 1c2f04937b
commit 24d481ecae
1 changed files with 3 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
drivers/serial/8250.c
View file

@ -2272,7 +2272,9 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
/*
* Ask the core to calculate the divisor for us.
*/
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
baud = uart_get_baud_rate(port, termios, old,
port->uartclk / 16 / 0xffff,
port->uartclk / 16);
quot = serial8250_get_divisor(port, baud);
/*