From nobody Mon Feb 9 06:24:26 2026 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 A142DC83003 for ; Tue, 13 Jun 2023 13:01:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242489AbjFMNBS (ORCPT ); Tue, 13 Jun 2023 09:01:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242352AbjFMNBI (ORCPT ); Tue, 13 Jun 2023 09:01:08 -0400 Received: from mail-lf1-x12f.google.com (mail-lf1-x12f.google.com [IPv6:2a00:1450:4864:20::12f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48C971720 for ; Tue, 13 Jun 2023 06:01:04 -0700 (PDT) Received: by mail-lf1-x12f.google.com with SMTP id 2adb3069b0e04-4f74cda5f1dso2297982e87.3 for ; Tue, 13 Jun 2023 06:01:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rasmusvillemoes.dk; s=google; t=1686661262; x=1689253262; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=jgVb0YJLMNEKVO6C16PIZb2dGiXFxsfavrt5+857HKY=; b=AUEQfc0jRceHGb1w6P4Iboyfii+Xnq+70m0yflsKCMZERq9S1JJ7ZkrJzwjudlQH2V uERCy/ImP9fgYGc9vwqJMo31t2u3QJyyRRaTNgF1TnENWMHyDNPXq77+1z4uDaFg0eJr vkWox32OwQJI90VQZ9ruu7TSxJ1LFl8U+1eaA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686661262; x=1689253262; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=jgVb0YJLMNEKVO6C16PIZb2dGiXFxsfavrt5+857HKY=; b=XsLF71JQo4zfdKuB7zg17zXLU8yX/Aw2+QcwkCs6FHMRI99ALUnM6G/DflAqj4ZAxH lECB9YZKa2Fi7/1cM2Ccbo8xcwPQYkQx6WwqbkrrsAsGmF9HU+mWc48XBbLlOP4TKvWb 987RTksqBR/ductIvMNANcOAENistnR3jM0tXjrIx7uX/jueYAMN86vqaeziUNUgoGy7 D42OcX/GlVwvU2RIQd5Xm9PKl7CNOGFSQnkDsIxGpCRXv3JtsknCbAgLwoCNTM6LGWAh mH8nUYYtI/whF6v3x0JorEz191hc1rkCz0RjmnsQV/C8byN8D5RrGZt4+wIE/ac474TW ++Zw== X-Gm-Message-State: AC+VfDwHtpv0fIlBHRtIYjdzQJVecy1DieY6D/0XM46oR663T/hT72jQ QBcLJHJtpvUHRpUrh6SRvPQ84Q== X-Google-Smtp-Source: ACHHUZ5Qo6a3Iodn4uCUyUlQCY7xwqhM3pAPGUfek4nLzEXdGpHm5bVODFL/XdUnGOPmsJOid9eWoQ== X-Received: by 2002:a19:6515:0:b0:4f3:8c0d:41c1 with SMTP id z21-20020a196515000000b004f38c0d41c1mr4769696lfb.64.1686661262496; Tue, 13 Jun 2023 06:01:02 -0700 (PDT) Received: from prevas-ravi.prevas.se ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id u24-20020ac243d8000000b004f14ae5ded8sm1793786lfl.28.2023.06.13.06.01.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Jun 2023 06:01:02 -0700 (PDT) From: Rasmus Villemoes To: Alessandro Zummo , Alexandre Belloni Cc: Andy Shevchenko , devicetree@vger.kernel.org, Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-rtc@vger.kernel.org, Rasmus Villemoes , linux-kernel@vger.kernel.org Subject: [PATCH v2 1/8] rtc: isl12022: remove wrong warning for low battery level Date: Tue, 13 Jun 2023 15:00:03 +0200 Message-Id: <20230613130011.305589-2-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230613130011.305589-1-linux@rasmusvillemoes.dk> References: <20230612113059.247275-1-linux@rasmusvillemoes.dk> <20230613130011.305589-1-linux@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" There are multiple problems with this warning. First of all, it triggers way too often, in fact nearly on every boot, because the SR_LBAT85/SR_LBAT75 bits have another meaning when in battery backup mode. Quoting from the data sheet: LOW BATTERY INDICATOR 85% BIT (LBAT85) In Normal Mode (VDD), this bit indicates when the battery level has dropped below the pre-selected trip levels. [...] The LBAT85 detection happens automatically once every minute when seconds register reaches 59. In Battery Mode (VBAT), this bit indicates the device has entered into battery mode by polling once every 10 minutes. The LBAT85 detection happens automatically once when the minute register reaches x9h or x0h minutes. Similar wording applies to the LBAT75 bit. This means that if the device is powered off for more than 10 minutes, the LBAT85 bit is guaranteed to be set. Upon power-on, unless we're close enough to the end of a minute and/or the boot is slow enough that the second register passes 59, the LBAT85 bit is still set when the kernel (or early userspace) reads the RTC to set the system's wallclock time. Another minor problem is with the bit logic. If the 75% level is reached, logically we're also below 85%, so both bits would most likely be set. So even if the battery is below 75%, the warning would still say "voltage dropped below 85%". A third problem is that the driver and current DT binding offer no way to indicate the nominal battery level and/or settings of the Battery Level Monitor Trip Bits. Since the default value of the VB85TP[2:0] and VB75TP[2:0] bits are 000, this means the actual setting of the LBAT85/LBAT75 bits in VDD mode doesn't happen until the battery is below 2.125V/1.875V, which for a standard 3V battery is way too late. A fourth problem is emitting this warning from ->read_time: util-linux' hwclock will, in the absence of support for getting an interrupt when the seconds counter is updated, issue ioctl(RTC_RD_TIME) in a busy-loop until it sees a change in the seconds field. In that case, if the battery low bits are set (either genuinely, more than a minute after boot, due to the battery actually being low, or as above, bogusly shortly after boot), the kernel log is swamped with hundreds of identical warnings. Subsequent patches will add such bindings and driver support, and also proper support for RTC_VL_READ. For now, remove the broken warning. Signed-off-by: Rasmus Villemoes --- drivers/rtc/rtc-isl12022.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/rtc/rtc-isl12022.c b/drivers/rtc/rtc-isl12022.c index e68a79b5e00e..ebd66b835cef 100644 --- a/drivers/rtc/rtc-isl12022.c +++ b/drivers/rtc/rtc-isl12022.c @@ -141,12 +141,6 @@ static int isl12022_rtc_read_time(struct device *dev, = struct rtc_time *tm) if (ret) return ret; =20 - if (buf[ISL12022_REG_SR] & (ISL12022_SR_LBAT85 | ISL12022_SR_LBAT75)) { - dev_warn(dev, - "voltage dropped below %u%%, date and time is not reliable.\n", - buf[ISL12022_REG_SR] & ISL12022_SR_LBAT85 ? 85 : 75); - } - dev_dbg(dev, "raw data is sec=3D%02x, min=3D%02x, hr=3D%02x, mday=3D%02x, mon=3D%02x,= year=3D%02x, wday=3D%02x, sr=3D%02x, int=3D%02x", buf[ISL12022_REG_SC], --=20 2.37.2