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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7084C433F5 for ; Mon, 18 Apr 2022 18:50:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347496AbiDRSxN (ORCPT ); Mon, 18 Apr 2022 14:53:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347492AbiDRSxB (ORCPT ); Mon, 18 Apr 2022 14:53:01 -0400 Received: from aposti.net (aposti.net [89.234.176.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3A5F2F39B; Mon, 18 Apr 2022 11:50:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=crapouillou.net; s=mail; t=1650307797; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gTydCTe/7cAyLlIMweK5uFG1GYH9QzGk2uqsrqg28Oo=; b=HEvosaXqUAJaM43ThX9L/5w3WJ5BrXLFRg2EUIjxmL/MdlW+LOPXb1fnpElIc/Dgkc9Xng aeTnMj+yhDrIWcGaCC964jixem3O3aRwgx1mr8OTX9vqrAhNRorIHgk/BaM4exFfF3q13i 23jRa11lv0AXN4W/s74zEnjewY7HOwI= From: Paul Cercueil To: Alessandro Zummo , Alexandre Belloni Cc: list@opendingux.net, linux-rtc@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, Paul Cercueil Subject: [PATCH 3/5] rtc: jz4740: Reset scratchpad register on power loss Date: Mon, 18 Apr 2022 19:49:31 +0100 Message-Id: <20220418184933.13172-4-paul@crapouillou.net> In-Reply-To: <20220418184933.13172-1-paul@crapouillou.net> References: <20220418184933.13172-1-paul@crapouillou.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On power loss, reading the RTC value would fail as the scratchpad lost its magic value, until the hardware clock was set once again. To avoid that, reset the RTC value to Epoch in the probe if we detect that the scratchpad lost its magic value. Signed-off-by: Paul Cercueil --- drivers/rtc/rtc-jz4740.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/drivers/rtc/rtc-jz4740.c b/drivers/rtc/rtc-jz4740.c index 119baf168b32..aac5f68bf626 100644 --- a/drivers/rtc/rtc-jz4740.c +++ b/drivers/rtc/rtc-jz4740.c @@ -42,6 +42,9 @@ /* Magic value to enable writes on jz4780 */ #define JZ_RTC_WENR_MAGIC 0xA55A +/* Value written to the scratchpad to detect power losses */ +#define JZ_RTC_SCRATCHPAD_MAGIC 0x12345678 + #define JZ_RTC_WAKEUP_FILTER_MASK 0x0000FFE0 #define JZ_RTC_RESET_COUNTER_MASK 0x00000FE0 @@ -134,10 +137,11 @@ static int jz4740_rtc_ctrl_set_bits(struct jz4740_rtc *rtc, uint32_t mask, static int jz4740_rtc_read_time(struct device *dev, struct rtc_time *time) { struct jz4740_rtc *rtc = dev_get_drvdata(dev); - uint32_t secs, secs2; + uint32_t secs, secs2, magic; int timeout = 5; - if (jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD) != 0x12345678) + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) return -EINVAL; /* If the seconds register is read while it is updated, it can contain a @@ -169,7 +173,8 @@ static int jz4740_rtc_set_time(struct device *dev, struct rtc_time *time) if (ret) return ret; - return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, 0x12345678); + return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, + JZ_RTC_SCRATCHPAD_MAGIC); } static int jz4740_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) @@ -307,6 +312,7 @@ static int jz4740_rtc_probe(struct platform_device *pdev) struct jz4740_rtc *rtc; unsigned long rate; struct clk *clk; + uint32_t magic; int ret, irq; rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL); @@ -369,6 +375,18 @@ static int jz4740_rtc_probe(struct platform_device *pdev) /* Each 1 Hz pulse should happen after (rate) ticks */ jz4740_rtc_reg_write(rtc, JZ_REG_RTC_REGULATOR, rate - 1); + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) { + /* + * If the scratchpad doesn't hold our magic value, then a + * power loss occurred. Reset to Epoch. + */ + struct rtc_time time; + + rtc_time64_to_tm(0, &time); + jz4740_rtc_set_time(dev, &time); + } + ret = devm_rtc_register_device(rtc->rtc); if (ret) return ret; -- 2.35.1