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=-8.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 7AF02C433E0 for ; Mon, 22 Feb 2021 21:27:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2685164E25 for ; Mon, 22 Feb 2021 21:27:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231807AbhBVV10 (ORCPT ); Mon, 22 Feb 2021 16:27:26 -0500 Received: from relay6-d.mail.gandi.net ([217.70.183.198]:33165 "EHLO relay6-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231624AbhBVV1Z (ORCPT ); Mon, 22 Feb 2021 16:27:25 -0500 X-Originating-IP: 90.65.108.55 Received: from localhost (lfbn-lyo-1-1676-55.w90-65.abo.wanadoo.fr [90.65.108.55]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay6-d.mail.gandi.net (Postfix) with ESMTPSA id 2892AC0002; Mon, 22 Feb 2021 21:26:26 +0000 (UTC) Date: Mon, 22 Feb 2021 22:26:26 +0100 From: Alexandre Belloni To: Sebastian Reichel Cc: Philipp Zabel , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , Rob Herring , Alessandro Zummo , David Airlie , Daniel Vetter , Miquel Raynal , devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rtc@vger.kernel.org, linux-mtd@lists.infradead.org, kernel@collabora.com Subject: Re: [PATCHv1 1/6] rtc: m41t80: add support for protected clock Message-ID: References: <20210222171247.97609-1-sebastian.reichel@collabora.com> <20210222171247.97609-2-sebastian.reichel@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-rtc@vger.kernel.org On 22/02/2021 22:20:47+0100, Alexandre Belloni wrote: > On 22/02/2021 18:12:42+0100, Sebastian Reichel wrote: > > Congatec's QMX6 system on module (SoM) uses a m41t62 as RTC. The > > modules SQW clock output defaults to 32768 Hz. This behaviour is > > used to provide the i.MX6 CKIL clock. Once the RTC driver is probed, > > the clock is disabled and all i.MX6 functionality depending on > > the 32 KHz clock has undefined behaviour. On systems using hardware > > watchdog it seems to likely trigger a lot earlier than configured. > > > > The proper solution would be to describe this dependency in DT, > > but that will result in a deadlock. The kernel will see, that > > i.MX6 system clock needs the RTC clock and do probe deferral. > > But the i.MX6 I2C module never becomes usable without the i.MX6 > > CKIL clock and thus the RTC's clock will not be probed. So from > > the kernel's perspective this is a chicken-and-egg problem. > > > > Reading the previous paragraph, I was going to suggest describing the > dependency and wondering whether this would cause a circular dependency. > I guess this will keep being an issue for clocks on an I2C or SPI bus... > > > Technically everything is fine by not touching anything, since > > the RTC clock correctly enables the clock on reset (i.e. on > > battery backup power loss) and also the bootloader enables it > > in case a kernel without this support has been booted. > > > > The 'protected-clocks' property is already in use for some clocks > > that may not be touched because of firmware limitations and is > > described in Documentation/devicetree/bindings/clock/clock-bindings.txt. > > > > Signed-off-by: Sebastian Reichel > Acked-by: Alexandre Belloni Or maybe you expected me to apply the patch, how are the following patches dependent on this one? -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com