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=-5.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 310B1C2D0A3 for ; Mon, 2 Nov 2020 19:32:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8963420786 for ; Mon, 2 Nov 2020 19:32:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b="q0ztW9m7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725927AbgKBTca (ORCPT ); Mon, 2 Nov 2020 14:32:30 -0500 Received: from mout01.posteo.de ([185.67.36.65]:34999 "EHLO mout01.posteo.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725791AbgKBTc2 (ORCPT ); Mon, 2 Nov 2020 14:32:28 -0500 Received: from submission (posteo.de [89.146.220.130]) by mout01.posteo.de (Postfix) with ESMTPS id 3E5C416005F for ; Mon, 2 Nov 2020 20:32:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.de; s=2017; t=1604345546; bh=jWgTqBnGhp0TRhbZW5Wm7Jv7qoJ+OhqUWSuJH3odXrQ=; h=Subject:To:Cc:From:Autocrypt:Date:From; b=q0ztW9m7e/aXW+p9wrXbzHqQceM03Ol82FCui7+3ki+DTzsGueEzr8kX07/LRAA2y uGJp/ADxo73VOqAsGkWUwgpdNmp/AvPs814KS/+WDahGKoI2KtGsyaqJ19mVVDkHar js+GcSFpJsx3R1W9hvlkblac5QCRrwbDpb18/FyhKu/MGuf3I02zjeTldTbt5ZfQjo touddqlkxgDpO9WxPj4q/zO7f1n77wSi6JFB9x1Q0Q1Gllz+k1lCt/MswrFSir7sQ1 VQYmJL1KDS0YHhJnO3PDeZXg6aekpGao8DWSDe7+o17bbcuYVEebfVuz388A12zUbi WXYaf2Ic235WQ== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4CQ32x2PdBz6tmP; Mon, 2 Nov 2020 20:32:25 +0100 (CET) Subject: Re: mcp251xfd on RPi 5.4 downstream To: Thomas.Kopp@microchip.com, mkl@pengutronix.de, drew@beagleboard.org Cc: socketcan@hartkopp.net, linux-can@vger.kernel.org, josh@macchina.cc References: <6a7061a4-771d-6703-1e30-273050abfb9d@posteo.de> <2593d8e0-2d42-0461-e2e1-86a71b415476@pengutronix.de> <3d19330b-860b-7d76-bc6d-768a7b00ed4b@pengutronix.de> <3a5f81d6-13ba-71b8-67a7-fe6e8a13f84a@posteo.de> <3b7b6353-0493-210a-7c14-e7ccc1067365@pengutronix.de> <08a1fb36-5efb-27d8-f5b9-bd2a923479a2@pengutronix.de> <9e9db79d-9357-19bd-0584-3f97ed49c731@posteo.de> From: Patrick Menschel Autocrypt: addr=menschel.p@posteo.de; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org >> It may be a blunt guess, but according to page 99 >> >> https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm27 >> 11/rpi_DATA_2711_1p0.pdf >> >> Pin 26 is pulldown. So it works if it remains unused because the pin is >> input with pulldown thus the chip is selected by default. >> >> I don't know if the CE pin can actually work if there is no matching alt >> function in pinselect register. >> >> -- >> Patrick > Do you suggest that the communication works with a permanent low on CS/CE? > Without the CS/CE pin having edges you will not be able to send multiple > commands. The driver is writing/reading multiple times when bringing up the > chip. If you have a permanent low that will fail. So somehow the CS does > generate the right edges. > > Thomas > As mentioned it's a blunt guess. If there is more to CE functionality then just enabling the recipient to listen, then I'm obviously wrong. -- Patrick