[SeaBIOS] [PATCH] Extend tools/readserial.py to support serial port timing calibration.

[Kevin O'Connor]

On Sat, Jul 09, 2011 at 07:23:23PM -0400, Kevin O'Connor wrote:
> On Sat, Jul 09, 2011 at 07:01:00PM -0400, Kevin O'Connor wrote:
> > > I also noticed coreboot enables the uart fifos. This is not beneficial
> > > because the simple polling logic used by coreboot and SeaBIOS cannot utilize
> > > the transmit fifo.
> > 
> > Could the fifos being enabled be the cause of the slow down even after
> > the SeaBIOS serial polling fix?
> 
> I ran a quick test with the fifos disabled.  Unfortunately, I still
> get a slower transmit rate - off by about 8us per character on my
> e350m1 - even with the seabios patch I sent separately.  Weird.

Bleh - that was really dumb.  I had:

    while ((inb(CONFIG_DEBUG_SERIAL_PORT+SEROFF_LSR) & 0x40) != 0x40)

instead of:

    while ((inb(CONFIG_DEBUG_SERIAL_PORT+SEROFF_LSR) & 0x20) != 0x20)

That bit error led me down a wrong path..  It's odd that Linux seems
to have the same issue.

-Kevin