From owner-freebsd-stable Mon Apr 24 13:31:57 2000 Delivered-To: freebsd-stable@freebsd.org Received: from caffeine.gerp.org (caffeine.gerp.org [216.80.26.45]) by hub.freebsd.org (Postfix) with SMTP id 6A4F437BBD7 for ; Mon, 24 Apr 2000 13:31:46 -0700 (PDT) (envelope-from kdulzo@caffeine.gerp.org) Received: (qmail 10444 invoked by uid 100); 24 Apr 2000 20:14:08 -0000 Date: Mon, 24 Apr 2000 15:13:35 -0500 From: "Kevin M. Dulzo" To: Jim King Subject: Re: sio interrupt handler problem Message-ID: <20000424151335.A10431@caffeine.gerp.org> References: <5564.000424@pd.chel.ru><20000424114057.A692@pir.net> <14596.37283.563515.214828@localhost.nantes.kisoft-services.com> <003801bfae25$39a6d100$a44b8486@jking> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1us In-Reply-To: <003801bfae25$39a6d100$a44b8486@jking>; from king@sstar.com on Mon, Apr 24, 2000 at 02:42:09PM -0500 Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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. > > > 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. > > > Jim Couldn't something like this be turned into a tuneable nob via sysctl? Software settable UART buffering is available on MS OSes, could we not mimic this in someway? -Kevin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message