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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A573C433F5 for ; Thu, 21 Oct 2021 20:23:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0210560F9F for ; Thu, 21 Oct 2021 20:23:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232108AbhJUUZ3 (ORCPT ); Thu, 21 Oct 2021 16:25:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232107AbhJUUZV (ORCPT ); Thu, 21 Oct 2021 16:25:21 -0400 Received: from mail-ed1-x52d.google.com (mail-ed1-x52d.google.com [IPv6:2a00:1450:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4EBDEC061224 for ; Thu, 21 Oct 2021 13:23:03 -0700 (PDT) Received: by mail-ed1-x52d.google.com with SMTP id w19so2032016edd.2 for ; Thu, 21 Oct 2021 13:23:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=FoCS2Of8JxmjrHA0ciYvVff3O/0PQ9jcwIzAZgxkZS4=; b=xZaim99sf1bhVyq0cz+y+AGLha2Rs85XXTMdgylFks8k1SKW0pM6Tf4ovbIHHTJm7a f5k7Kc/crnsPDQWV92l8nrxWK26UPS0UA+rBvHaM2ffryWvXOWI8H+Vc12Tq2LKjphVs wzjP56H05iTP5rL9g/zdrJ2L6raRN3zejvpMVVn9veKSfip5gnXk19/TJYGMM3Cs6Xro NiV7ep6Y1Es7b4YDM39aRn7Qzq1XDw0L/B1nl0TMSmfxpJ8SPH0oTL+60Uvt5Zohr7Vz 5qn3lg2t4TNzdHxT2nEQBsMV5NBCg2afSX3CPIj72gsISFp6/SGISgJ86s1J9/wes7lJ ge4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=FoCS2Of8JxmjrHA0ciYvVff3O/0PQ9jcwIzAZgxkZS4=; b=o8yHifaNSU/EUntdNjTOYmooN53/kcuZQF4A5zpJy65QTafEoiYTNB5oLney7fTffe QqTdcHttIpACyv1xPOuqF3955WDY4N71Ew2heVQZRordG/64UTtjhFGGfqT1GcX55CYX OtwWUQ3aMDQIl2HmFDbYYurHCtMqvLp4IFJocQareNWZtL5w//ILykAXE+YCj2L/5CCs 4dY3wmByGxfgAVzDSMBwBMOgY3mUAM0wLaLmFIys9gCuraabDKE87kmg+0s31MLYrPQq lao2lCSQvPAvt162BlyUebhauAXF8vBcEpMFx+OzU0Jl1170n2cWqmOTxuhcIVvbWEej fTPg== X-Gm-Message-State: AOAM531l3YCAVCznw1bOgZGq/DVm2f7isP5VP04avQy/ry4wJAgTxv0/ myPWLhhdMEDQ+mhNifp9pv/cYQ== X-Google-Smtp-Source: ABdhPJzNwPC1x2uv2WuF6tsvx9+hXHVKaMH2Rdw3WklOnENLjkro6EEJq++2tcWXb/uSqXPiBfPnBg== X-Received: by 2002:a17:906:181a:: with SMTP id v26mr2131988eje.478.1634847781841; Thu, 21 Oct 2021 13:23:01 -0700 (PDT) Received: from localhost ([31.134.121.151]) by smtp.gmail.com with ESMTPSA id u18sm3293456eds.86.2021.10.21.13.23.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Oct 2021 13:23:01 -0700 (PDT) From: Sam Protsenko To: Alessandro Zummo , Alexandre Belloni , Krzysztof Kozlowski Cc: linux-rtc@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 3/3] rtc: s3c: Add time range Date: Thu, 21 Oct 2021 23:22:56 +0300 Message-Id: <20211021202256.28517-4-semen.protsenko@linaro.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211021202256.28517-1-semen.protsenko@linaro.org> References: <20211021202256.28517-1-semen.protsenko@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This RTC driver starts counting from 2000 to avoid Y2K problem. Also it only supports 100 years range for all RTCs. Provide that info to RTC framework. Also remove check for 100 years range in s3c_rtc_settime(), as RTC core won't pass any invalid values to the driver, now that correct range is set. Here is the rationale on 100 years range limitation. Info on different Samsung RTCs (credit goes to Krzysztof Kozlowski): - All S3C chips have only 8-bit wide year register (can store 100 years range in BCD format) - S5Pv210 and Exynos chips have 12-bit year register (can store 1000 years range in BCD format) But in reality we usually can't make use of those 12 bits either: - RTCs might think that both 2000 and 2100 years are leap years. So when the YEAR register is 0, RTC goes from 28 Feb to 29 Feb, and when the YEAR register is 100, RTC also goes from 28 Feb to 29 Feb. This is of course incorrect: RTC breaks leap year criteria, which breaks the time contiguity, which leads to inability to use the RTC after year of 2099. It was found for example on Exynos850 SoC. - Despite having 12 bits for holding the year value, RTC might overflow the year value internally much earlier. For example, on Exynos850 the RTC overflows when YEAR=159, making the next YEAR=0. This way RTC actually has range of 160 years, not 1000 as one may think. All that said, there is no sense in trying to increase the time range for more than 100 years on RTCs that seem capable of that. It also doesn't have too much practical value -- current hardware will be probably obsolete by 2100. Tested manually on Exynos850 RTC: $ date -s "1999-12-31 23:59:50" $ hwclock -w -f /dev/rtc0 $ date -s "2100-01-01 00:00:00" $ hwclock -w -f /dev/rtc0 $ date -s "2000-01-01 00:00:00" $ hwclock -w -f /dev/rtc0 $ hwclock -r -f /dev/rtc0 $ date -s "2099-12-31 23:59:50" $ hwclock -w -f /dev/rtc0 $ hwclock -r -f /dev/rtc0 Signed-off-by: Sam Protsenko --- Changes in v2: - Removed check for 100 years range in s3c_rtc_settime() - Improved the commit message drivers/rtc/rtc-s3c.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c index d1baf655c008..db529733c9c4 100644 --- a/drivers/rtc/rtc-s3c.c +++ b/drivers/rtc/rtc-s3c.c @@ -219,11 +219,6 @@ static int s3c_rtc_settime(struct device *dev, struct rtc_time *tm) rtc_tm.tm_year -= 100; rtc_tm.tm_mon += 1; - if (rtc_tm.tm_year < 0 || rtc_tm.tm_year >= 100) { - dev_err(dev, "rtc only supports 100 years\n"); - return -EINVAL; - } - return s3c_rtc_write_time(info, &rtc_tm); } @@ -478,6 +473,8 @@ static int s3c_rtc_probe(struct platform_device *pdev) } info->rtc->ops = &s3c_rtcops; + info->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000; + info->rtc->range_max = RTC_TIMESTAMP_END_2099; ret = devm_rtc_register_device(info->rtc); if (ret) -- 2.30.2