From owner-freebsd-hackers  Tue Nov 11 12:47:39 1997
Return-Path: <owner-freebsd-hackers>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.7/8.8.7) id MAA21401
          for hackers-outgoing; Tue, 11 Nov 1997 12:47:39 -0800 (PST)
          (envelope-from owner-freebsd-hackers)
Received: from out1.ibm.net (out1.ibm.net [165.87.194.252])
          by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id MAA21391
          for <hackers@freebsd.org>; Tue, 11 Nov 1997 12:47:30 -0800 (PST)
          (envelope-from mouth@ibm.net)
Received: from slip129-37-53-153.ca.us.ibm.net (slip129-37-53-153.ca.us.ibm.net [129.37.53.153]) by out1.ibm.net (8.8.5/8.6.9) with SMTP id UAA101086; Tue, 11 Nov 1997 20:45:57 GMT
From: mouth@ibm.net (John Kelly)
To: Bruce Evans <bde@zeta.org.au>
Cc: hackers@freebsd.org
Subject: Status of 650 UART support
Date: Tue, 11 Nov 1997 21:47:13 GMT
Message-ID: <3468ce08.353607@smtp-gw01.ny.us.ibm.net>
References: <199711111110.DAA15487@hub.freebsd.org>
In-Reply-To: <199711111110.DAA15487@hub.freebsd.org>
X-Mailer: Forte Agent 1.01/16.397
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from quoted-printable to 8bit by hub.freebsd.org id MAA21396
Sender: owner-freebsd-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

On Tue, 11 Nov 1997 03:10:02 -0800 (PST), Bruce Evans
<bde@zeta.org.au> wrote:

> > /kernel: sio2: 40 more interrupt-level buffer overflows (total 828)
> 
> This message is unusual.  It means that the system is overloaded with
> interrupt processing.  Apparently the modem can keep up without input
> flow control (into it), but FreeBSD can't.

I'm getting that "interrupt-level buffer overflow" message when I use
the 650 UART support.  As long as I run the UARTs in 550 compatibility
mode, they work fine.  My kernel is 3.0-971108-SNAP.

I've looked at the source in sio.c and I see where the 650 auto
CTS/RTS flow control is turned on, but I've made little other progress
towards comprehending sio.c

>static  char const * const      error_desc[] = {.
>       "silo overflow",
>       "interrupt-level buffer overflow",
>       "tty-level buffer overflow",
>};

Can anyone explain the difference between these three types of
overflows?

John