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 70650C43334 for ; Fri, 1 Jul 2022 15:40:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229685AbiGAPks convert rfc822-to-8bit (ORCPT ); Fri, 1 Jul 2022 11:40:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229570AbiGAPkr (ORCPT ); Fri, 1 Jul 2022 11:40:47 -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 DEFD03FBF7 for ; Fri, 1 Jul 2022 08:40:46 -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 1o7Ikf-00006u-HT; Fri, 01 Jul 2022 17:40:13 +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 1o7IkZ-003oKw-3y; Fri, 01 Jul 2022 17:40:10 +0200 Received: from pza by lupine with local (Exim 4.94.2) (envelope-from ) id 1o7Ikb-000AJF-Sx; Fri, 01 Jul 2022 17:40:09 +0200 Message-ID: <2d0f161e879175dea310ed77797f83f29c2b9503.camel@pengutronix.de> Subject: Re: [PATCH v2 0/2] i2c: Add new driver for Renesas RZ/V2M controller From: Philipp Zabel To: Geert Uytterhoeven Cc: Phil Edworthy , Rob Herring , Krzysztof Kozlowski , Wolfram Sang , Andy Shevchenko , Jarkko Nikula , Sam Protsenko , Sven Peter , Jan Dabros , Lukas Bulwahn , Tyrone Ting , Arnd Bergmann , Olof Johansson , Biju Das , Geert Uytterhoeven , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Linux I2C , Linux-Renesas Date: Fri, 01 Jul 2022 17:40:09 +0200 In-Reply-To: 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 Geert, On Mi, 2022-06-29 at 19:18 +0200, Geert Uytterhoeven wrote: > Hi Philipp, > > On Wed, Jun 29, 2022 at 6:21 PM Philipp Zabel wrote: > > On Di, 2022-06-28 at 20:45 +0100, Phil Edworthy wrote: > > > 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? > > In response to v1, I wrote > > > That is actually an integration issue, not an i2c controller issue. > > > > Perhaps we need a RESET_IS_CRITICAL flag, cfr. CLK_IS_CRITICAL, > > to be set by the reset provider? I would just let the reset controller driver implement this by disabling _assert and _reset for those firmware-shared resets. regards Philipp