From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.hugovil.com (mail.hugovil.com [162.243.120.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6760A3D9DA1; Tue, 25 Aug 2026 13:28:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=162.243.120.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787664512; cv=none; b=QzWcsRh4lfyfL89W3Wv0vl73yYn7eXYvMqdXAVupGkZBYca/VKTdlkcIARxT8+mWukjD44W4fk3eloRjA779Xn9w4Kl6BDxRB6xXR2KNw9RBydIEuIXcJD+ETgYiK0sNJDSdG9/plmW0nEK8qrHyGyeIDB2q8WIDks1/ecVMoKc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787664512; c=relaxed/simple; bh=nXIDNeK0qAmNjsxIPbmvFt4k7Hi+Qik1VeWnEs/PdRg=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=u8c6g9RCpv+rKFGBZ7WM+PVW7Z0npJIW1Omd0A62lBhRJd0pZw6wz6hBxbBy8lVv6L6qjv0l26MN9xBHrHyHhQEmkJbDBPmBr42UN0HhIS81k3jjgTp3agOn3NKTlP+3YcLyoEXjxRMxSzgvo9nnuwEKZMI1Vmzlahj4KDegSfk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=hugovil.com; spf=pass smtp.mailfrom=hugovil.com; dkim=pass (1024-bit key) header.d=hugovil.com header.i=@hugovil.com header.b=DfX4JL+G; arc=none smtp.client-ip=162.243.120.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=hugovil.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=hugovil.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hugovil.com header.i=@hugovil.com header.b="DfX4JL+G" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=hugovil.com ; s=default; h=Content-Transfer-Encoding:Mime-Version:Message-Id:Subject:Cc: To:From:Date:subject:date:message-id:reply-to; bh=sYd2yF5EIMwqbxFouj8U9wGNvbFGrupAqlCE3ROY62Q=; b=DfX4JL+Gt7ImZPvxdBD/ZLXJak ZxGqdXdX7vHV/yE4DvXY5DeeEJu9Ew07W8dcDgcDWJ5SraL07tUUvDlLt5dWlcrp2gtxmgGsns2q4 DEgYjQdZwm9CVjkZ+nywHe1h773EOy8tJ8N3qaiIv/IK2yq1MZMQyYdRjJDyG7c1DW3s=; Received: from modemcable061.19-161-184.mc.videotron.ca ([184.161.19.61] helo=pettiford.lan) by mail.hugovil.com with esmtpa (Exim 4.98.2) (envelope-from ) id 1wyqkL-000000006II-2faw; Tue, 25 Aug 2026 08:59:22 -0400 Date: Tue, 25 Aug 2026 08:59:11 -0400 From: Hugo Villeneuve To: Stefan Kerkmann Cc: alexandre.belloni@bootlin.com, linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org, bruno.thomsen@gmail.com, giampiero@sferalabs.cc, p.rosenberger@kunbus.com, antonio@amsobr.com, Hugo Villeneuve Subject: Re: [PATCH 0/4] rtc: pcf2127: add support for battery low voltage detection Message-Id: <20260825085911.ba47297a8cb56028441114e8@hugovil.com> In-Reply-To: <84b6915f-328f-49b4-8466-1ea27a839cf3@pengutronix.de> References: <20260311200237.3531981-1-hugo@hugovil.com> <84b6915f-328f-49b4-8466-1ea27a839cf3@pengutronix.de> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-rtc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam_score: -2.0 X-Spam_bar: -- Hi Stefan, On Wed, 29 Jul 2026 17:18:59 +0200 Stefan Kerkmann wrote: > Hello Hugo, > > On 3/11/26 21:02, Hugo Villeneuve wrote: > > From: Hugo Villeneuve > > > > Hello, > > this patch series adds support for battery low voltage detection configuration > > for RTC devicesm, with specifc changes targeted at the pcf2127/2131 devices. > > > > The origin of this patch goes back to the initial commit to add support for the > > PCF2131 device. On the PCF2131, the battery low voltage detection is disabled by > > default at the hardware level, contrary to the PCF2127 where it is enabled by > > default. Because of that, a lot of people are stuck with a PCF2131 RTC device > > using a battery backup, but unable to use it! > > > > A lot of people are writing to me in private emails to report this as a bug > > in the PCF2131 driver. Others (and me) have proposed to implement device tree > > properties to enable these functions, but this was rejected [1][2][3]. > > > > It is important to note that some projects do not have the luxury to modify > > the bootloder to enable that function at boot, and for these having a DT > > property that could be put in a DT overlay would simplify a lot their life. > > Also having to rely on a userspace application to configure the RTC is also > > not ideal, as some projects use stock Debian distros (for example), and > > adding a new application to their repository is not trivial or easy. > > > > So as the next best thing, this patch aims to add what is missing in the driver, > > the ability to enable/disable the battery low voltage detection with ioctls, > > similarly to what is done with the BSM. > > > > Thank you for the series. We have customer that has this exact use case: Ok, a lot of people affected by this... > > Enabling the backup battery switch-over and low battery detection on a pcf2131 > rtc. With util-linux's hwclock the former can already be enabled e.g. hwclock > --param-set bsm and for the later this patch series would enable it as well. > > > This patch has been tested on a custom board with a PCF2131 and using my > > userspace application: > > > > git clone -b batlow_param git@git.hugovil.com:repos/hvrtc.git > > > > If this series gets merged I can sent a PR to util-linux to enable the low > battery detection via hwclock as well. Good. Unfortunately, I haven't received any feedback from the RTC maintainer(s) about this series, nor have I received any answers to my previous inquiries about this problem. I send patches to other kernel subsystem, and eventually I always receive feedback, but RTC seems to be in a different category. I sometimes wonder if there is still an active RTC maintainer... Hugo. > > Thank you. > > > > Link: https://lore.kernel.org/linux-rtc/20190910143945.9364-1-bruno.thomsen@gmail.com/ [1] > > Link: https://lore.kernel.org/linux-rtc/20191211163354.GC1463890@piout.net/ [2] > > Link: https://lore.kernel.org/linux-rtc/20230123170731.6064430c50f5fb7b484d8734@hugovil.com/ [3] > > > > Hugo Villeneuve (4): > > rtc: pcf2127: remove redundant break statement in switch-case > > rtc: pcf2127: add pcf2127_pwrmng_get/set > > rtc: add battery low voltage detection feature > > rtc: pcf2127: support battery low voltage detection function > > > > drivers/rtc/rtc-pcf2127.c | 94 ++++++++++++++++++++++++++++++--------- > > include/uapi/linux/rtc.h | 7 ++- > > 2 files changed, 80 insertions(+), 21 deletions(-) > > > > > > base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f > > Best regards, > Stefan > > -- > Pengutronix e.K. | Stefan Kerkmann | > Steuerwalder Str. 21 | https://www.pengutronix.de/ | > 31137 Hildesheim, Germany | Phone: +49-5121-206917-128 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 | -- Hugo Villeneuve