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Date:      Sun, 5 May 2013 12:59:17 +0100
From:      =?ISO-8859-1?Q?Miguel_Barbosa_Gon=E7alves?= <m@mbg.pt>
To:        freebsd-questions@freebsd.org
Subject:   Disable FIFO on UART
Message-ID:  <CAEdntmtta6LQ3U62sod8vGggTT5f1mqoWE0cf0wma=MCs-uvNA@mail.gmail.com>

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Hi!

Back in FreeBSD 7 there was a flag to disable the FIFO on the sio
device driver. From
http://www.freebsd.org/cgi/man.cgi?query=sio&apropos=0&sektion=0&manpath=FreeBSD+7.4-stable&arch=default&format=html:

Meaning of flags:
0x00001   shared IRQs
0x00002   disable FIFO
0x00004   no AST/4 compatible IRQ control register
0x00008   recover sooner from lost output interrupts
0x00010   device is potential system console
0x00020   device is forced to become system console
0x00040   device is reserved for low-level IO (e.g. for remote kernel debugging)
0x00080   use this port for remote kernel debugging
0x0??00   minor number of master port
0x10000   PPS timestamping on CTS instead of DCD
0x20000   device is assumed to use a 16650A-type (extended FIFO) chip

Now with FreeBSD 8 which uses the UART device driver there's no option for that.

I am looking to reduce the jitter I am getting on the serial port when
connecting a GPS to the server.

Can anyone help?

Regards,
Miguel



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