From owner-freebsd-hardware  Tue May 20 15:25:57 1997
Return-Path: <owner-hardware>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.5/8.8.5) id PAA01211
          for hardware-outgoing; Tue, 20 May 1997 15:25:57 -0700 (PDT)
Received: from lariat.lariat.org (ppp0.lariat.org@[129.72.251.2])
          by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id PAA01205
          for <HARDWARE@FreeBSD.ORG>; Tue, 20 May 1997 15:25:55 -0700 (PDT)
Received: from solo.lariat.org ([129.72.251.10])
	by lariat.lariat.org (8.8.5/8.8.5) with SMTP id QAA05174;
	Tue, 20 May 1997 16:24:55 -0600 (MDT)
Message-Id: <3.0.1.32.19970520125159.006dbe70@lariat.org>
X-Sender: brett@lariat.org
X-Mailer: Windows Eudora Pro Version 3.0.1 (32)
Date: Tue, 20 May 1997 12:51:59 -0600
To: rberndt@nething.com, WELCHDW@wofford.edu, HARDWARE@FreeBSD.ORG
From: Brett Glass <brett@lariat.org>
Subject: Re: isa bus and boca multiport boards
Cc: WELCHDW@wofford.edu
In-Reply-To: <8825649D.00771D31.00@IWND1.infoworld.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Sender: owner-hardware@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

At 04:14 PM 5/20/97 -0400, you wrote:
 
>Since the entire set of ports must be scanned whenever an interrupt occurs,
>maybe there is too much delay in getting to the upper ports. Something gets
>locked up if they overflow. I left several messages, but no one could
>figure it out.

Maybe the sio driver should be recoded in optimized ASM. I can see some
major C inefficiencies in it, including lots of repeated pointer
dereferences and control structures that the compiler would probably
optimize poorly. I've generated super-tight assembler for serial I/O.

A stopgap might be be use a couple of IRQs for the different ports, if the
board lets you do it. I put no more than 4 UARTs on an IRQ in my system
because the driver loops over the UARTS at least twice per IRQ.

--Brett