From owner-freebsd-current@freebsd.org  Mon Jul  1 17:14:51 2019
Return-Path: <owner-freebsd-current@freebsd.org>
Delivered-To: freebsd-current@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 90D8215E0230
 for <freebsd-current@mailman.ysv.freebsd.org>;
 Mon,  1 Jul 2019 17:14:51 +0000 (UTC)
 (envelope-from phk@critter.freebsd.dk)
Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222])
 by mx1.freebsd.org (Postfix) with ESMTP id B0197882C1;
 Mon,  1 Jul 2019 17:14:50 +0000 (UTC)
 (envelope-from phk@critter.freebsd.dk)
Received: from critter.freebsd.dk (v-critter.freebsd.dk [192.168.55.3])
 by phk.freebsd.dk (Postfix) with ESMTP id C05A52025629;
 Mon,  1 Jul 2019 17:14:49 +0000 (UTC)
Received: from critter.freebsd.dk (localhost [127.0.0.1])
 by critter.freebsd.dk (8.15.2/8.15.2) with ESMTPS id x61HEnIn093150
 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO);
 Mon, 1 Jul 2019 17:14:49 GMT (envelope-from phk@critter.freebsd.dk)
Received: (from phk@localhost)
 by critter.freebsd.dk (8.15.2/8.15.2/Submit) id x61HEmK9093149;
 Mon, 1 Jul 2019 17:14:48 GMT (envelope-from phk)
To: Warner Losh <imp@bsdimp.com>
cc: Ian Lepore <ian@freebsd.org>, Andriy Gapon <avg@freebsd.org>,
 FreeBSD Current <freebsd-current@freebsd.org>
Subject: Re: i2c bit banging timeout for SCL
In-reply-to: <CANCZdfoFBvmxPtnEL4GOqXTvp6Zd-xrtja4rmUO1rAcy0JdeSw@mail.gmail.com>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <a3538c10-2438-a287-77db-ad390078b274@FreeBSD.org>
 <7e5d8a06bc2d46263262369464e9348b82263847.camel@freebsd.org>
 <CANCZdfoFBvmxPtnEL4GOqXTvp6Zd-xrtja4rmUO1rAcy0JdeSw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <93147.1562001288.1@critter.freebsd.dk>
Content-Transfer-Encoding: quoted-printable
Date: Mon, 01 Jul 2019 17:14:48 +0000
Message-ID: <93148.1562001288@critter.freebsd.dk>
X-Rspamd-Queue-Id: B0197882C1
X-Spamd-Bar: +++
Authentication-Results: mx1.freebsd.org
X-Spamd-Result: default: False [3.95 / 15.00]; ARC_NA(0.00)[];
 FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4];
 NEURAL_SPAM_SHORT(0.82)[0.821,0]; MIME_GOOD(-0.10)[text/plain];
 DMARC_NA(0.00)[freebsd.dk]; AUTH_NA(1.00)[];
 NEURAL_SPAM_MEDIUM(0.89)[0.893,0]; RCVD_COUNT_THREE(0.00)[4];
 TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[];
 MX_GOOD(-0.01)[cached: phk.freebsd.dk];
 NEURAL_SPAM_LONG(0.88)[0.883,0]; R_SPF_NA(0.00)[];
 FORGED_SENDER(0.30)[phk@phk.freebsd.dk,phk@critter.freebsd.dk];
 RCVD_NO_TLS_LAST(0.10)[]; R_DKIM_NA(0.00)[];
 MIME_TRACE(0.00)[0:+];
 ASN(0.00)[asn:1835, ipnet:130.225.0.0/16, country:EU];
 FROM_NEQ_ENVFROM(0.00)[phk@phk.freebsd.dk,phk@critter.freebsd.dk];
 IP_SCORE(0.06)[ip: (0.11), ipnet: 130.225.0.0/16(0.05), asn: 1835(0.15),
 country: EU(-0.00)]
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
 <freebsd-current.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-current>, 
 <mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current/>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
 <mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 01 Jul 2019 17:14:51 -0000

--------
In message <CANCZdfoFBvmxPtnEL4GOqXTvp6Zd-xrtja4rmUO1rAcy0JdeSw@mail.gmail=
.com>, Warner Losh writes:

>The only issue, really, is that this timeout is a busy loop and there may
>be I/O bus contention introduced on these systems.

Does it have to be a busy loop for the entire duration ?

Spin for the median, timeout+poll for the rest of the time ?

-- =

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    =

Never attribute to malice what can adequately be explained by incompetence=
.