From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCHv2] i2c-mpc: Correct I2C reset procedure Date: Wed, 21 Jun 2017 23:59:24 +0200 Message-ID: <20170621215924.GB2419@katana> References: <20170511122033.22471-1-joakim.tjernlund@infinera.com> <1494947612.7509.24.camel@infinera.com> <1495547252.17446.60.camel@infinera.com> <20170529210419.GA2527@katana> <1496095395.17446.111.camel@infinera.com> <20170621213647.GA2419@katana> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="QTprm0S8XgL7H0Dt" Return-path: Received: from www.zeus03.de ([194.117.254.33]:40192 "EHLO mail.zeus03.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751667AbdFUV70 (ORCPT ); Wed, 21 Jun 2017 17:59:26 -0400 Content-Disposition: inline In-Reply-To: <20170621213647.GA2419@katana> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Joakim Tjernlund Cc: "oss@buserror.net" , "linux-i2c@vger.kernel.org" --QTprm0S8XgL7H0Dt Content-Type: text/plain; charset=us-ascii Content-Disposition: inline > Toggling 9x even means you could then write something somewhere > which in case of a PMIC can be really dangerous. I am partly wrong here because you send a START beforehand. And devices are required to reset their state machine when they detect a START (I2C Specs 3.1.10, Note 4). So, it *shouldn't* be dangerous. If all devices follow that rule, that is... However, you can only send START when SDA is not stuck. And still, this whole toggling is to reanimate a stuck SDA. So, it still looks to me that it doesn't make sense to have START & STOP around the toggling and rather have a single STOP before you try toggling. Makes sense? --QTprm0S8XgL7H0Dt Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAllK7DsACgkQFA3kzBSg KbZ7VhAAnmVO2lrEhnH7DVh7jbwP0c1MzltDciKIGzhWeclvTnkdzAXgQ7Gc8plc FttnK2grHz6IXqlMLczHBdj8F1ISZSKq9vwhaV50/jzCC5xzbfiMV4WMKbshZ+Nu I+XhjFtAzcyc52Wik30zz1+igj7lLReoKSL3l/W2oultFUglSFbx6BEwaVsiNn9x n0JiMKrVt/QYC7kz+SnGhlEPI0SXmlE7SVgDIlqa344LQ1qlRvjoiwRi8sHtGP4m 7oGF3qodjcii6llPxdAXRXr2cA8cNhfgppupqJsIQRIl/YAsMQs4GHAEvWS7tKlA Ik2/FkmnryMC+MfdpdMcUTayaP5SfbqfY6hkvpFJnWTGpzRC5tXJbW9xpgHaAhyI FoQ52uIKo7QZ/66cKOwO3xmbHRP0FyQETAAplNaPr84xOYB0WQPl/Hxs0BQ+ahfn 97ELgJnM4njyQassSjzy4UkTtirSDvTPoEifQ8FiOwKYwaRtRltnlGLfMARzSNIw BQJD9oszp60xYzM4N3H9JUkREml8mke+I3SXuS3/+1MMEMo7erHsMY7KGvstJjHK UyftuO8ybJLDMqSyps9E0lOHM6Dr8L+qsGI8o52OUvFbTuRXfx9zORhZZN0r0O3F 09J87SrE/qPuVYt4z5fI4nuM1hxjgcHfj9ClBF/tGtG7PHwod28= =3T1M -----END PGP SIGNATURE----- --QTprm0S8XgL7H0Dt--