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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 A0113C6778A for ; Tue, 24 Jul 2018 07:26:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D65320875 for ; Tue, 24 Jul 2018 07:26:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D65320875 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=the-dreams.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388476AbeGXIbn (ORCPT ); Tue, 24 Jul 2018 04:31:43 -0400 Received: from sauhun.de ([88.99.104.3]:54538 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388394AbeGXIbn (ORCPT ); Tue, 24 Jul 2018 04:31:43 -0400 Received: from localhost (p54B3332A.dip0.t-ipconnect.de [84.179.51.42]) by pokefinder.org (Postfix) with ESMTPSA id D9CF3634593; Tue, 24 Jul 2018 09:26:37 +0200 (CEST) Date: Tue, 24 Jul 2018 09:26:37 +0200 From: Wolfram Sang To: Phil Reid Cc: Wolfram Sang , linux-i2c@vger.kernel.org, linux-renesas-soc@vger.kernel.org, kernel@pengutronix.de, Jarkko Nikula , Andy Shevchenko , Mika Westerberg , linux-kernel@vger.kernel.org Subject: Re: [PATCH/RFT 1/6] i2c: designware: use open drain for recovery GPIO Message-ID: <20180724072637.smhlrx4kpyh6hvwa@ninjato> References: <20180713210920.3648-1-wsa+renesas@sang-engineering.com> <20180713210920.3648-2-wsa+renesas@sang-engineering.com> <20180717090920.zy6lkeqlcewhrfs5@ninjato> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ofht27vhe5ktigiu" Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ofht27vhe5ktigiu Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Phil, > > So, it is not possible to read SCL status then? Hmm, currently a working > > get_scl is required... =2E.. > > Well, I don't know much about this IP core and how/where it is used. I > > just wonder what happens if another user comes along using an > > open-drain GPIO. Is that possible? > >=20 > > I assume it is the same with SDA? Non open-drain? Output only? > >=20 >=20 > Just had a closer look at how it's setup here. > Maybe the following helps. Thanks for the detailed explanation. I am just afraid it is a litle too detailed for me. I am not sure if I can read it correctly: When you read the SCL/SDA GPIO, does it return the true state of the SCL/SDA line or does it just reflect the value it was set to output? > There's no concept of HiZ internally in the FPGA. Which probably means SDA is to be treated the same as SCL -> push/pull. > If there was some kinda of OpenDrain gpio driver that modelled a FET > driven by a push pull GPIO I guess it could be made to work. Still, that sounds quite unlikely to me, so we can for now assume that all designware users will have push/pull? Disclaimer: I have zero experience with this core, I don't know how hard it is to modify or which versions are out there. Thanks for your help, Wolfram --ofht27vhe5ktigiu Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAltW1KkACgkQFA3kzBSg KbYqQA/7BLzkFJlpp83m/0LTH8LUFT1nWqSkrPjWGUw5PF91E91L4NNfHUHQLazy jDKPrnTqnCz3WPMHrPHeRWRXZXCdv6s172wI2ubd8Xt1mH1T2fwu4X1g4yvVfDZj xnF+Y0v9A/KVFTaM29rJo9pq6PAvJOip8haW3yC29+kF9tIJjBxkcJim0cZ4m7Yr WVK37EzDI6x2FRfGWG2cy5bxUCRldCnDEmrkXS37X2PPjB4I81gZKh2T1bTfP4ac VWwYMcNXfGpnNNBBB7ZftSdAq16hXCxIg/xyoM/xzfOxCMLWaEGeOJTQvzYyUkN1 PkZ1TO2fTa2GyB1zfCvIIRFZxNiUmuNvIWFG7a81q1pkIpfd45GznplnyW95elji LkkcwBu0UL7vdEKXWsnF0qjqArKy/NtbSIMTRQHXc7Pazu1hlQkVhwVhFKBsrIFS 0ylIQg4+eK5WMLGSuZgpfLw3GQascmbPb53Cny18O9lV20Cx4d3qrXdCefMFH3Df AF8XbcWELKzvVtrMrg1p9QtflCBYOx+Dq/tUzrDKU1Ufumamf9YBTPGkv4LMXJ0Y L7mqscD9RYZYn1RKAS5QB6cagz5i7dPrivreTyDPG4SdLHCqU4F4LAuhI/g/Aaxa muLCmtzU6y1vKOdgF3odUucqZeFKP2Nla0KzIJc3ubpnlfvwKTc= =1srA -----END PGP SIGNATURE----- --ofht27vhe5ktigiu--