atmel_serial losing characters under libmodbus

[schen@mvista.com (Steve Chen)]

On Wed, 2009-11-11 at 14:59 +0100, Josef Holzmayr wrote:
> christian pellegrin wrote:
> > On Wed, Nov 11, 2009 at 1:44 PM, Josef Holzmayr
> > <zentrale.at.work@gmail.com> wrote:
> >> When using libmodbus on an atmel_serial line, it seems to lose about 1 char
> >> in 50 that it's supposed to receive. This is independet of the baud rate, it
> >> happens everywhere from 2400 to 19200. Full code excerpt from the lib is
> >> below, but basically reading is just an select/read pair. Are there some
> >> known issues with that particular tty device?
> >>
> > 
> > Hi, the only serial port on AT91 that gives me troubles is the DBGU
> > port which shares the interrupt with the timer tick. You see a lot of
> > serial overruns there if you have the kernel compiled with HZ=1000 on
> > that port (usually ttyS0).
> > 
> 
> Thanks for the hint, but iv'e got this problem reproducable on ttyS2 and 
> ttyS4. CONFIG_HZ is 128, and whats really interesting: if you use an 
> usb-to-serial converter instead, everything works like a charm.
> 
I experienced serial port dropping characters at random some time back.
The problem turned out to be FIFO size in software was set larger than
FIFO size in actual hardware...  Just a thought...

Steve