From patchwork Fri May 13 11:03:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miquel Raynal X-Patchwork-Id: 572285 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 8EBDBC41535 for ; Fri, 13 May 2022 11:03:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379710AbiEMLDs (ORCPT ); Fri, 13 May 2022 07:03:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379701AbiEMLDq (ORCPT ); Fri, 13 May 2022 07:03:46 -0400 Received: from relay7-d.mail.gandi.net (relay7-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::227]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34BAC2A2F42; Fri, 13 May 2022 04:03:43 -0700 (PDT) Received: (Authenticated sender: miquel.raynal@bootlin.com) by mail.gandi.net (Postfix) with ESMTPSA id 076E12000E; Fri, 13 May 2022 11:03:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1652439822; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cg7Lu7ZMGG3YSb9uhqDTPpQD4l1ydcR7jEcl/8VvVF0=; b=Gj4h0fT6HnnYiXYWrIU+f3BuhkQFWuNOyYg1xRoNouDpoFRfZO8TlqRiRvhFwXJovNdvZm oJ+I0k5AcW2ECXjSZiKdEp8C4eU90GRuL27x2Gd1zrYXYKaAn2eoldckExO0k28tf+OdPv aB7KrjG9JuRGwII5EyZufz71trrSoGOSejgZDvMydqA8ifgkmkgvPCRBF5JXpQiQrBYgFO EIKZQ6yiwKgiTEYOXW3ei9VBFbi0EjfbhOJGrLRiwoBjLYumE+JF93mbubdAzs1jCc/udF +pgQuM4pKyZ+1FpJ19KCJrL2wceok1ceJI7OQFRpBjdgVv3NflxSYXlr+p2Eeg== From: Miquel Raynal To: Alessandro Zummo , Alexandre Belloni , Rob Herring , Krzysztof Kozlowski , Geert Uytterhoeven , Magnus Damm Cc: Miquel Raynal , linux-rtc@vger.kernel.org, linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org, Gareth Williams , Milan Stevanovic , Jimmy Lalande , Pascal Eberhard , Thomas Petazzoni , Herve Codina , Clement Leger Subject: [PATCH v6 4/5] rtc: rzn1: Add oscillator offset support Date: Fri, 13 May 2022 13:03:26 +0200 Message-Id: <20220513110327.261652-5-miquel.raynal@bootlin.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220513110327.261652-1-miquel.raynal@bootlin.com> References: <20220513110327.261652-1-miquel.raynal@bootlin.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org The RZN1 RTC can compensate the imprecision of the oscillator up to approximately 190ppm. Seconds can last slightly shorter or longer depending on the configuration. Below ~65ppm of correction, we can change the time spent in a second every minute, which is the most accurate compensation that the RTC can offer. Above, the compensation will be active every 20s. Signed-off-by: Miquel Raynal --- drivers/rtc/rtc-rzn1.c | 73 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) diff --git a/drivers/rtc/rtc-rzn1.c b/drivers/rtc/rtc-rzn1.c index 7ee190daa651..f340793d9fc7 100644 --- a/drivers/rtc/rtc-rzn1.c +++ b/drivers/rtc/rtc-rzn1.c @@ -247,12 +247,85 @@ static int rzn1_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm) return 0; } +static int rzn1_rtc_read_offset(struct device *dev, long *offset) +{ + struct rzn1_rtc *rtc = dev_get_drvdata(dev); + unsigned int ppb_per_step; + bool subtract; + u32 val; + + val = readl(rtc->base + RZN1_RTC_SUBU); + ppb_per_step = val & RZN1_RTC_SUBU_DEV ? 1017 : 3051; + subtract = val & RZN1_RTC_SUBU_DECR; + val &= 0x3F; + + if (!val) + *offset = 0; + else if (subtract) + *offset = -(((~val) & 0x3F) + 1) * ppb_per_step; + else + *offset = (val - 1) * ppb_per_step; + + return 0; +} + +static int rzn1_rtc_set_offset(struct device *dev, long offset) +{ + struct rzn1_rtc *rtc = dev_get_drvdata(dev); + unsigned int steps; + int stepsh, stepsl; + u32 val; + int ret; + + /* + * Check which resolution mode (every 20 or 60s) can be used. + * Between 2 and 124 clock pulses can be added or substracted. + * + * In 20s mode, the minimum resolution is 2 / (32768 * 20) which is + * close to 3051 ppb. In 60s mode, the resolution is closer to 1017. + */ + stepsh = DIV_ROUND_CLOSEST(offset, 1017); + stepsl = DIV_ROUND_CLOSEST(offset, 3051); + + if (stepsh >= -0x3E && stepsh <= 0x3E) { + /* 1017 ppb per step */ + steps = stepsh; + val |= RZN1_RTC_SUBU_DEV; + } else if (stepsl >= -0x3E && stepsl <= 0x3E) { + /* 3051 ppb per step */ + steps = stepsl; + } else { + return -ERANGE; + } + + if (!steps) + return 0; + + if (steps > 0) { + val |= steps + 1; + } else { + val |= RZN1_RTC_SUBU_DECR; + val |= (~(-steps - 1)) & 0x3F; + } + + ret = readl_poll_timeout(rtc->base + RZN1_RTC_CTL2, val, + !(val & RZN1_RTC_CTL2_WUST), 100, 2000000); + if (ret) + return ret; + + writel(val, rtc->base + RZN1_RTC_SUBU); + + return 0; +} + static const struct rtc_class_ops rzn1_rtc_ops = { .read_time = rzn1_rtc_read_time, .set_time = rzn1_rtc_set_time, .read_alarm = rzn1_rtc_read_alarm, .set_alarm = rzn1_rtc_set_alarm, .alarm_irq_enable = rzn1_rtc_alarm_irq_enable, + .read_offset = rzn1_rtc_read_offset, + .set_offset = rzn1_rtc_set_offset, }; static int rzn1_rtc_probe(struct platform_device *pdev)