Re: Serial issue

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

On Fri, Aug 18, 2006 at 04:54:13PM -0400, Lee Revell wrote:
> On Fri, 2006-08-18 at 21:34 +0100, Russell King wrote:
> > On Fri, Aug 18, 2006 at 04:28:36PM -0400, Lee Revell wrote:
> > > On Fri, 2006-08-18 at 16:25 -0400, Mark Hounschell wrote:
> > > > Take it from someone who actually still uses dumb terminals every day,
> > > > any thing over 9600 baud still requires some kind of flow control for
> > > > reliable consistent operation. Software (Xon/Xoff) and or hardware
> > > > (RTS/RTS/DTE) flow control.
> > > > 
> > > 
> > > Any idea why the serial console does not work at all with flow control
> > > enabled (regardless of whether the host runs Linux or another OS)?
> > 
> > I use serial console with flow control and haven't seen any problems.
> > 
> > Can you describe your issue with more detail?
> > 
> > What actions are required to get this "does not work at all" state?
> > 
> > Are you passing a kernel parameter to enable flow control?
> > 
> > Are you saying that you get kernel messages if flow control is disabled,
> > but if you subsequently enable flow control, and provoke a kernel message,
> > you don't see any messages?  When you re-disable flow control, you do?
> > 
> 
> I believe the flow control problem is due to my cable.
> 
> Anyway I don't want to confuse the issue: the problem that I want to
> solve (or at least explain) is that while the serial console works with
> the host serial port in both interrupt and polled mode, kermit file
> transfers only work in polled mode ("setserial /dev/ttyS0 irq 0").

If you're talking about sending via a polled port, the average data rate
is probably slow enough that the receiving side can keep up.  But in
interrupt mode, it's probably a stream of characters at the specified
baud rate, which results in lost characters.

That explaination doesn't resolve the receiving via a polled port though.

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