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Message-ID: <006901bfae30$9f74d300$a44b8486@jking>
From: "Jim King" <king@sstar.com>
To: "Kevin M. Dulzo" <kdulzo@caffeine.gerp.org>,
	<freebsd-stable@freebsd.org>
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Subject: Re: sio interrupt handler problem
Date: Mon, 24 Apr 2000 16:03:53 -0500
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On Monday, April 24, 2000 3:13 PM, Kevin M. Dulzo wrote:
> On Mon, Apr 24, 2000 at 02:42:09PM -0500, Jim King wrote:
> >
> > One thing I've done in the past to overcome serial port problems is to
patch
> > sys/isa/sio.c to set the FIFO receive trigger level to 8 bytes instead
of 14
> > (FIFO_RX_MEDH instead of FIFO_RX_HIGH).  If you have a piece of hardware
or
> > a misbehaved driver that's causing high interrupt latency this change be
> > really beneficial, and greatly outweighs the higher interrupt overhead
when
> > using an 8 byte trigger.
> >
> > <soapbox>
> > An 8 byte trigger is a safer option that causes better operation on
weird
> > hardware without signifcantly changing anything on good hardware.  I
really
> > wish sio.c would be changed to set the trigger to 8 bytes by default, or
at
> > least have a flags option to change the trigger level.
> > </soapbox>
> >
> > Jim
>
> <hint> Couldn't something like this be turned into a tuneable nob
> via sysctl? </hint>  Software settable UART buffering is available on MS
> OSes, could we not mimic this in someway?
>
> -Kevin

Sounds like a good idea to me.

Jim




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