From patchwork Mon Feb 22 17:12:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Reichel X-Patchwork-Id: 12099217 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_GIT 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 3F1FDC433E6 for ; Mon, 22 Feb 2021 17:17:01 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 079ED64DE9 for ; Mon, 22 Feb 2021 17:17:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 079ED64DE9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=collabora.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 794BE89F49; Mon, 22 Feb 2021 17:16:57 +0000 (UTC) Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3E3AA89F5F for ; Mon, 22 Feb 2021 17:13:06 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: sre) with ESMTPSA id BC0EB1F451E2 Received: by jupiter.universe (Postfix, from userid 1000) id 4E8464800D9; Mon, 22 Feb 2021 18:12:51 +0100 (CET) From: Sebastian Reichel To: Sebastian Reichel , Philipp Zabel , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team Subject: [PATCHv1 1/6] rtc: m41t80: add support for protected clock Date: Mon, 22 Feb 2021 18:12:42 +0100 Message-Id: <20210222171247.97609-2-sebastian.reichel@collabora.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210222171247.97609-1-sebastian.reichel@collabora.com> References: <20210222171247.97609-1-sebastian.reichel@collabora.com> MIME-Version: 1.0 X-Mailman-Approved-At: Mon, 22 Feb 2021 17:16:54 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-rtc@vger.kernel.org, Alessandro Zummo , Alexandre Belloni , devicetree@vger.kernel.org, David Airlie , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Rob Herring , linux-mtd@lists.infradead.org, Miquel Raynal , kernel@collabora.com, linux-arm-kernel@lists.infradead.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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. 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 --- Documentation/devicetree/bindings/rtc/rtc-m41t80.txt | 1 + drivers/rtc/rtc-m41t80.c | 3 +++ 2 files changed, 4 insertions(+) diff --git a/Documentation/devicetree/bindings/rtc/rtc-m41t80.txt b/Documentation/devicetree/bindings/rtc/rtc-m41t80.txt index c746cb221210..ea4bbf5c4282 100644 --- a/Documentation/devicetree/bindings/rtc/rtc-m41t80.txt +++ b/Documentation/devicetree/bindings/rtc/rtc-m41t80.txt @@ -19,6 +19,7 @@ Optional properties: - interrupts: rtc alarm interrupt. - clock-output-names: From common clock binding to override the default output clock name +- protected-clocks: Bool, if set operating system should not handle clock. - wakeup-source: Enables wake up of host system on alarm Example: diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c index 160dcf68e64e..3296583853a8 100644 --- a/drivers/rtc/rtc-m41t80.c +++ b/drivers/rtc/rtc-m41t80.c @@ -546,6 +546,9 @@ static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80) struct clk_init_data init; int ret; + if (of_property_read_bool(node, "protected-clocks")) + return 0; + /* First disable the clock */ ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON); if (ret < 0)