From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0A6EC43603 for ; Tue, 17 Dec 2019 18:18:28 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AEB5020733 for ; Tue, 17 Dec 2019 18:18:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="L2pbEK+T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AEB5020733 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zonque.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 5052A850; Tue, 17 Dec 2019 19:17:35 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 5052A850 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1576606705; bh=tSPwUhU6Cf29OkCTZ67YmrS0sZv4D0LiaRwBaO1QDn8=; h=To:References:From:Date:In-Reply-To:Cc:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=L2pbEK+TDtvgRQQJbIxCzpM7SHymZFGtxBUD6IQdpTdHiChRUYC/6wqDlhufSePwj 1KNGHgUfABBJMjmWEArbH/x4yW53hpuJywBsMMEAuI4aEzK7jc/Th0ue13zOj57tUP xFCatn6hf/Tzkn4dvxV7pBDEgqIP7A0E43zNXEEo= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id C6969F8020B; Tue, 17 Dec 2019 19:17:34 +0100 (CET) Received: by alsa1.perex.cz (Postfix, from userid 50401) id C18CAF80234; Tue, 17 Dec 2019 19:17:32 +0100 (CET) Received: from mail.bugwerft.de (mail.bugwerft.de [46.23.86.59]) by alsa1.perex.cz (Postfix) with ESMTP id 7D821F8020B for ; Tue, 17 Dec 2019 19:17:28 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 7D821F8020B Received: from [192.168.178.106] (pD95EF574.dip0.t-ipconnect.de [217.94.245.116]) by mail.bugwerft.de (Postfix) with ESMTPSA id 6E681281A97; Tue, 17 Dec 2019 18:11:03 +0000 (UTC) To: Luca Ceresoli , Wolfram Sang References: <20191209183511.3576038-1-daniel@zonque.org> <20191209183511.3576038-9-daniel@zonque.org> <64adf5d7-754a-f1da-aa9b-11579c5a2780@lucaceresoli.net> <20191212163315.GA3932@kunai> <482316ef-775a-cb7b-015e-e00463503e6b@zonque.org> <4f2e1332-eac3-e54d-5de8-b84a76cb1a34@lucaceresoli.net> From: Daniel Mack Message-ID: Date: Tue, 17 Dec 2019 19:17:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <4f2e1332-eac3-e54d-5de8-b84a76cb1a34@lucaceresoli.net> Content-Language: en-US Cc: devicetree@vger.kernel.org, alsa-devel@alsa-project.org, lars@metafoo.de, sboyd@kernel.org, mturquette@baylibre.com, linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org, robh+dt@kernel.org, broonie@kernel.org, linux-i2c@vger.kernel.org, pascal.huerst@gmail.com, lee.jones@linaro.org, linux-clk@vger.kernel.org Subject: Re: [alsa-devel] [PATCH 07/10] i2c: Add driver for AD242x bus controller X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" Hi Luca, On 12/17/19 9:35 AM, Luca Ceresoli wrote: > On 15/12/19 21:27, Daniel Mack wrote: >> The a2b code has to tell the 'master node' the final destination of the >> payload by programming registers on its primary i2c address, and then >> forwards the messages to its secondary i2c address. The layout of the >> messages don't change, and neither do the flags; i2c messages are being >> sent as i2c messages, except their addresses are changed, a bit like NAT >> in networking. That procedure is described on page 3-4 of the TRM, >> "Remote Peripheral I2C Accesses". >> >> The 'real' i2c master that handles the hardware bus is responsible for >> adding start conditions, and as the messages as such are untouched, I >> believe it should do the right thing. The code in my xfer functions >> merely suppresses reprogramming remote addresses by remembering the last >> one that was used, but that is independent of the start conditions on >> the wire. > > My concern is not about the start condition, it's about the *repeated* > start condition. > > The first question is whether the A2B chips can do it. What if the host > processor sets a slave chip address and then issues two messages > separated by a repeated start condition? Will the slave transceiver emit > a repeated start condition too? Ah, alright. Thanks for taking the time to explain. I'll have to do some measurements with a hardware analyzer. Will revisit this then, and either provide an implementation that handles such cases correctly, or a comment to explain that the hardware can't do it. Best regards, Daniel _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org https://mailman.alsa-project.org/mailman/listinfo/alsa-devel