From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751680AbdGaUrP convert rfc822-to-8bit (ORCPT ); Mon, 31 Jul 2017 16:47:15 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:47265 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751610AbdGaUrM (ORCPT ); Mon, 31 Jul 2017 16:47:12 -0400 Date: Mon, 31 Jul 2017 22:46:58 +0200 From: Boris Brezillon To: Wolfram Sang Cc: linux-i2c@vger.kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org, Greg Kroah-Hartman , Arnd Bergmann , Przemyslaw Sroka , Arkadiusz Golec , Alan Douglas , Bartosz Folta , Damian Kos , Alicja Jurasik-Urbaniak , Jan Kotas , Cyprian Wronka , Alexandre Belloni , Thomas Petazzoni , Nishanth Menon , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 2/5] i3c: Add core I3C infrastructure Message-ID: <20170731224658.3991e2fd@bbrezillon> In-Reply-To: <20170731191721.GA1542@katana> References: <1501518290-5723-1-git-send-email-boris.brezillon@free-electrons.com> <1501518290-5723-3-git-send-email-boris.brezillon@free-electrons.com> <20170731191721.GA1542@katana> X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le Mon, 31 Jul 2017 21:17:21 +0200, Wolfram Sang a écrit : > > +This document is just a brief introduction to the I3C protocol and the concepts > > +it brings on the table. If you need more information, please refer to the MIPI > > +I3C specification. > > I wish I could. > > > + > > +Introduction > > +============ > > + > > +The I3C (I-Cube-C) is a MIPI standardized protocol designed to overcome I2C > > "Eye-three-See", according to: > http://eecatalog.com/sensors/2017/07/05/after-35-years-of-i2c-i3c-improves-capability-and-performance/ I remember hearing eye-cube-see during the discussion we had with Cadence engineers but I might wrong. I'll double check (or maybe I'll just drop any mention of the pronunciation). > > > +Backward compatibility with I2C devices > > +======================================= > > + > > +The I3C protocol has been designed to be backward compatible with I2C devices. > > +This backward compatibility allows one to connect a mix of I2C and I3C devices > > +on the same bus, though, in order to be really efficient, I2C devices should > > +be equipped with 50 ns spike filters. > > I just found a slide which says I3C does not support clock stretching. > That should be mentioned here, too. > You're right, clock stretching is not allowed, and if devices without a 50ns spike filter are connected to the bus, it lowers the maximum speed for all devices, which renders I3C kind of useless. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Brezillon Subject: Re: [RFC 2/5] i3c: Add core I3C infrastructure Date: Mon, 31 Jul 2017 22:46:58 +0200 Message-ID: <20170731224658.3991e2fd@bbrezillon> References: <1501518290-5723-1-git-send-email-boris.brezillon@free-electrons.com> <1501518290-5723-3-git-send-email-boris.brezillon@free-electrons.com> <20170731191721.GA1542@katana> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20170731191721.GA1542@katana> Sender: linux-kernel-owner@vger.kernel.org To: Wolfram Sang Cc: linux-i2c@vger.kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org, Greg Kroah-Hartman , Arnd Bergmann , Przemyslaw Sroka , Arkadiusz Golec , Alan Douglas , Bartosz Folta , Damian Kos , Alicja Jurasik-Urbaniak , Jan Kotas , Cyprian Wronka , Alexandre Belloni , Thomas Petazzoni , Nishanth Menon , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell List-Id: devicetree@vger.kernel.org Le Mon, 31 Jul 2017 21:17:21 +0200, Wolfram Sang a écrit : > > +This document is just a brief introduction to the I3C protocol and the concepts > > +it brings on the table. If you need more information, please refer to the MIPI > > +I3C specification. > > I wish I could. > > > + > > +Introduction > > +============ > > + > > +The I3C (I-Cube-C) is a MIPI standardized protocol designed to overcome I2C > > "Eye-three-See", according to: > http://eecatalog.com/sensors/2017/07/05/after-35-years-of-i2c-i3c-improves-capability-and-performance/ I remember hearing eye-cube-see during the discussion we had with Cadence engineers but I might wrong. I'll double check (or maybe I'll just drop any mention of the pronunciation). > > > +Backward compatibility with I2C devices > > +======================================= > > + > > +The I3C protocol has been designed to be backward compatible with I2C devices. > > +This backward compatibility allows one to connect a mix of I2C and I3C devices > > +on the same bus, though, in order to be really efficient, I2C devices should > > +be equipped with 50 ns spike filters. > > I just found a slide which says I3C does not support clock stretching. > That should be mentioned here, too. > You're right, clock stretching is not allowed, and if devices without a 50ns spike filter are connected to the bus, it lowers the maximum speed for all devices, which renders I3C kind of useless.