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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5A08C43334 for ; Wed, 29 Jun 2022 16:21:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232170AbiF2QVY convert rfc822-to-8bit (ORCPT ); Wed, 29 Jun 2022 12:21:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231964AbiF2QVW (ORCPT ); Wed, 29 Jun 2022 12:21:22 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F32B35DDF for ; Wed, 29 Jun 2022 09:21:21 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1o6aR1-00060d-Vh; Wed, 29 Jun 2022 18:21:00 +0200 Received: from [2a0a:edc0:0:900:1d::4e] (helo=lupine) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.94.2) (envelope-from ) id 1o6aQu-003QoU-LD; Wed, 29 Jun 2022 18:20:56 +0200 Received: from pza by lupine with local (Exim 4.94.2) (envelope-from ) id 1o6aQx-000DVO-GS; Wed, 29 Jun 2022 18:20:55 +0200 Message-ID: Subject: Re: [PATCH v2 0/2] i2c: Add new driver for Renesas RZ/V2M controller From: Philipp Zabel To: Phil Edworthy , Rob Herring , Krzysztof Kozlowski Cc: Wolfram Sang , Andy Shevchenko , Jarkko Nikula , Sam Protsenko , Sven Peter , Jan Dabros , Lukas Bulwahn , Tyrone Ting , Arnd Bergmann , Olof Johansson , Biju Das , Geert Uytterhoeven , devicetree@vger.kernel.org, linux-i2c@vger.kernel.org, linux-renesas-soc@vger.kernel.org Date: Wed, 29 Jun 2022 18:20:55 +0200 In-Reply-To: <20220628194526.111501-1-phil.edworthy@renesas.com> References: <20220628194526.111501-1-phil.edworthy@renesas.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT User-Agent: Evolution 3.38.3-1 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-i2c@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Hi Phil, On Di, 2022-06-28 at 20:45 +0100, Phil Edworthy wrote: > Hi, > > The Renesas RZ/V2M SoC (r9a09g011) has a new i2c controller. This series > add the driver. One annoying problem is that the SoC uses a single reset > line for two i2c controllers, and unfortunately one of the controllers > is managed by some firmware, not by Linux. Therefore, the driver just > deasserts the reset. This sounds scary. If the driver is never loaded, and the reset is never deasserted, what happens to the firmware trying to access the other i2c controller? Does it hang? Or write to the reset controller registers to deassert the reset? If so, is there any protection against concurrent access from firmware and reset controller driver? regards Philipp