Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751757AbdG1Ilv (ORCPT ); Fri, 28 Jul 2017 04:41:51 -0400 Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.220]:12729 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbdG1Ilt (ORCPT ); Fri, 28 Jul 2017 04:41:49 -0400 X-RZG-AUTH: :P2MHfkW8eP4Mre39l357AZT/I7AY/7nT2yrT1q0ngWNsKR9DbcHksQH1pt3IXLh3PHrb X-RZG-CLASS-ID: mo00 Subject: Re: [PATCH v2 2/4] can: fixed-transceiver: Add documentation for CAN fixed transceiver bindings To: Franklin S Cooper Jr , Andrew Lunn , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, netdev@vger.kernel.org, linux-can@vger.kernel.org, wg@grandegger.com, mkl@pengutronix.de, robh+dt@kernel.org, quentin.schulz@free-electrons.com, sergei.shtylyov@cogentembedded.com References: <20170724230521.1436-1-fcooper@ti.com> <20170724230521.1436-3-fcooper@ti.com> <20170726164124.GL12049@lunn.ch> <355b90b3-97ce-1057-6617-d5d709449c48@hartkopp.net> <932602fe-d06a-7a17-5a0c-24265cf2e643@ti.com> <20170728045724.GA27903@airbook.vandijck-laurijssen.be> From: Oliver Hartkopp Message-ID: Date: Fri, 28 Jul 2017 10:41:40 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170728045724.GA27903@airbook.vandijck-laurijssen.be> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 854 Lines: 25 On 07/28/2017 06:57 AM, Kurt Van Dijck wrote: > So while _a_ transceiver may be spec'd to 1MBit during arbitration, > CAN FD packets may IMHO exceed that speed during data phase. When the bitrate is limited to 1Mbit/s you are ONLY allowed to use 1Mbit/s in the data section too (either with CAN or CAN FD). > That was the whole point of CAN FD: exceed the limits required for > correct arbitration on transceiver & wire. No. CAN FD is about a different frame format with up to 64 bytes AND the possibility to increase the bitrate in the data section of the frame. > So I do not agree on the single bandwidth limitation. The transceiver provides a single maximum bandwidth. It's an ISO Layer 1 device. > The word 'max-arbitration-bitrate' makes the difference very clear. I think you are mixing up ISO layer 1 and ISO layer 2. Regards, Oliver