在嵌入式開發(fā)中，我們經(jīng)常會遇到這樣的需求：設(shè)備需要在指定時(shí)間自動開機(jī)（比如物聯(lián)網(wǎng)網(wǎng)關(guān)定時(shí)喚醒采集數(shù)據(jù)、工業(yè)設(shè)備按班次啟動、服務(wù)器遠(yuǎn)程維護(hù)后自動重啟）。而實(shí)現(xiàn)這一功能的核心，往往離不開RTC（實(shí)時(shí)時(shí)鐘）芯片——它能在設(shè)備關(guān)機(jī)后依靠備用電池繼續(xù)計(jì)時(shí)，到預(yù)設(shè)時(shí)間后觸發(fā)硬件開機(jī)信號。

今天就以常見的HYM8563 RTC芯片（驅(qū)動已適配Linux 6.1內(nèi)核）為例，手把手教你在Linux和Android系統(tǒng)中配置RTC自動開機(jī)，附帶完整實(shí)操指令和問題排查技巧！

一、先搞懂：RTC自動開機(jī)的原理

簡單來說，RTC自動開機(jī)的核心是“RTC喚醒鬧鐘（Wake Alarm）”功能：

1.系統(tǒng)開機(jī)時(shí)，我們通過指令將「喚醒時(shí)間」寫入RTC芯片的鬧鐘寄存器；

2.執(zhí)行關(guān)機(jī)指令后，主板斷電，但RTC芯片靠備用電池繼續(xù)運(yùn)行，并倒計(jì)時(shí)等待喚醒時(shí)間；

3.當(dāng)RTC計(jì)時(shí)達(dá)到預(yù)設(shè)的喚醒時(shí)間，會輸出一個(gè)硬件觸發(fā)信號（如IRQ中斷），觸發(fā)主板開機(jī)。

本次實(shí)操的前提是：RTC驅(qū)動已正常加載（如文檔中適配的rtc-hym8563.c驅(qū)動，已支持喚醒鬧鐘功能），且主板硬件支持RTC喚醒（大部分嵌入式主板默認(rèn)支持）。

代碼修改：

diff --git a/kernel-6.1/drivers/rtc/rtc-hym8563.c b/kernel-6.1/drivers/rtc/rtc-hym8563.cindex 59759e26d47..ac75a50aa5b 100644--- a/kernel-6.1/drivers/rtc/rtc-hym8563.c+++ b/kernel-6.1/drivers/rtc/rtc-hym8563.c@@ -6,7 +6,7 @@ * Author: Heiko Stuebner  * * based on rtc-HYM8563- * Copyright (C) 2010 Rockchip Electronics Co., Ltd.+ * Copyright (C) 2010 ROCKCHIP, Inc. */
#include @@ -14,6 +14,7 @@#include #include #include +#include 
#define HYM8563_CTL10x00#define HYM8563_CTL1_TESTBIT(7)@@ -74,8 +75,6 @@#define HYM8563_TMR_CTL_MASK3
#define HYM8563_TMR_CNT0x0f-#define HYM8563_TMR_MAXCNT0xff-#define HYM8563_TMR_CFG(HYM8563_TMR_CTL_ENABLE | HYM8563_TMR_CTL_1)
struct hym8563 {struct i2c_client*client;@@ -83,10 +82,11 @@struct hym8563 {#ifdef CONFIG_COMMON_CLKstruct clk_hwclkout_hw;#endif-int alarm_or_timer_irq;-int alarm_tm_sec;};
+static struct i2c_client *mClient = NULL;+static struct rtc_wkalrm __alarm;+/* * RTC handling */@@ -98,8 +98,6 @@static int hym8563_rtc_read_time(struct device *dev, struct rtc_time *tm)int ret;
ret = i2c_smbus_read_i2c_block_data(client, HYM8563_SEC, 7, buf);-if (ret < 0)-return ret;
tm->tm_sec = bcd2bin(buf[0] & HYM8563_SEC_MASK);tm->tm_min = bcd2bin(buf[1] & HYM8563_MIN_MASK);@@ -112,6 +110,15 @@static int hym8563_rtc_read_time(struct device *dev, struct rtc_time *tm)return 0;}
+int hym8563_rtc_read_time_ex(struct rtc_time *tm) {+if(mClient == NULL) {+printk("%s failedn", __func__);+return -1;+}+return hym8563_rtc_read_time(&mClient->dev, tm);+}+EXPORT_SYMBOL(hym8563_rtc_read_time_ex);+static int hym8563_rtc_set_time(struct device *dev, struct rtc_time *tm){struct i2c_client *client = to_i2c_client(dev);@@ -156,26 +163,29 @@static int hym8563_rtc_set_time(struct device *dev, struct rtc_time *tm)return 0;}
+int hym8563_rtc_set_time_ex(struct rtc_time *tm) {+if(mClient == NULL) {+printk("%s failedn", __func__);+return -1;+}+return hym8563_rtc_set_time(&mClient->dev, tm);+}+EXPORT_SYMBOL(hym8563_rtc_set_time_ex);+static int hym8563_rtc_alarm_irq_enable(struct device *dev,unsigned int enabled){struct i2c_client *client = to_i2c_client(dev);-struct hym8563 *hym8563 = i2c_get_clientdata(client);int data;
data = i2c_smbus_read_byte_data(client, HYM8563_CTL2);if (data < 0)return data;
-if (enabled) {-if (hym8563->alarm_or_timer_irq)-data |= HYM8563_CTL2_TIE;-else-data |= HYM8563_CTL2_AIE;-} else {-data &= ~HYM8563_CTL2_TIE;+if (enabled)+data |= HYM8563_CTL2_AIE;+elsedata &= ~HYM8563_CTL2_AIE;-}
return i2c_smbus_write_byte_data(client, HYM8563_CTL2, data);};@@ -183,7 +193,6 @@static int hym8563_rtc_alarm_irq_enable(struct device *dev,static int hym8563_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm){struct i2c_client *client = to_i2c_client(dev);-struct hym8563 *hym8563 = i2c_get_clientdata(client);struct rtc_time *alm_tm = &alm->time;u8 buf[4];int ret;@@ -192,7 +201,8 @@static int hym8563_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)if (ret < 0)return ret;
-alm_tm->tm_sec = hym8563->alarm_tm_sec;+/* The alarm only has a minute accuracy */+alm_tm->tm_sec = 0;
alm_tm->tm_min = (buf[0] & HYM8563_ALM_BIT_DISABLE) ?-1 :@@ -211,7 +221,7 @@static int hym8563_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)if (ret < 0)return ret;
-if (ret & (HYM8563_CTL2_AIE | HYM8563_CTL2_TIE))+if (ret & HYM8563_CTL2_AIE)alm->enabled = 1;
return 0;@@ -220,45 +230,37 @@static int hym8563_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)static int hym8563_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm){struct i2c_client *client = to_i2c_client(dev);-struct hym8563 *hym8563 = i2c_get_clientdata(client);struct rtc_time *alm_tm = &alm->time;-struct rtc_time tm;-time64_t now, alarm, interval;u8 buf[4];int ret;
-ret = i2c_smbus_write_byte_data(client, HYM8563_TMR_CNT, 0);-if (ret < 0)-return ret;+/*+ * The alarm has no seconds so deal with it+ */+if (alm_tm->tm_sec) {+alm_tm->tm_sec = 0;+alm_tm->tm_min++;+if (alm_tm->tm_min >= 60) {+alm_tm->tm_min = 0;+alm_tm->tm_hour++;+if (alm_tm->tm_hour >= 24) {+alm_tm->tm_hour = 0;+alm_tm->tm_mday++;+if (alm_tm->tm_mday > 31)+alm_tm->tm_mday = 0;+}+}+}
-ret = i2c_smbus_write_byte_data(client, HYM8563_CTL2, 0);+ret = i2c_smbus_read_byte_data(client, HYM8563_CTL2);if (ret < 0)return ret;
-ret = hym8563_rtc_read_time(dev, &tm);+ret &= ~HYM8563_CTL2_AIE;++ret = i2c_smbus_write_byte_data(client, HYM8563_CTL2, ret);if (ret < 0)return ret;-alarm = rtc_tm_to_time64(alm_tm);-now = rtc_tm_to_time64(&tm);-interval = alarm - now;--/* store alarm tm_sec */-hym8563->alarm_tm_sec = alm_tm->tm_sec;--dev_info(dev, "%s: now:  %ptRn", __func__, &tm);-dev_info(dev, "%s: expired:%ptRn", __func__, alm_tm);-if (interval < HYM8563_TMR_MAXCNT) {-hym8563->alarm_or_timer_irq = 1;-/* set timer */-i2c_smbus_write_byte_data(client, HYM8563_TMR_CNT, (u8)interval);-dev_info(&client->dev, "%s: set %dm%ds timer, interval=%dsn",- __func__, ((u8)interval)/60, ((u8)interval)%60, (u8)interval);-} else {-hym8563->alarm_or_timer_irq = 0;-/* set alarm */-alm_tm->tm_sec = 0;-dev_info(dev, "%s: set alarm %ptRn", __func__, alm_tm);-}
buf[0] = (alm_tm->tm_min < 60 && alm_tm->tm_min >= 0) ?bin2bcd(alm_tm->tm_min) : HYM8563_ALM_BIT_DISABLE;@@ -287,6 +289,103 @@static const struct rtc_class_ops hym8563_rtc_ops = {.set_alarm= hym8563_rtc_set_alarm,};
+static int get_num(char *buf) {+char *index_start = buf;+int max_size;++if(buf == NULL)+return 0xff;++max_size = strlen(buf);+while('9' < *index_start || *index_start < '0') {+index_start++;+if(index_start - buf > max_size)+return 0xff;+}++return simple_strtol(index_start, NULL, 10);+}++static void get_alarm_from_usr(const char *buf) {+char *min_index, *hour_index, *mday_index, *wday_index;++min_index = strstr(buf, "min");+hour_index = strstr(buf, "hour");+mday_index = strstr(buf, "mday");+wday_index = strstr(buf, "wday");++__alarm.time.tm_min = get_num(min_index);+__alarm.time.tm_hour = get_num(hour_index);+__alarm.time.tm_mday = get_num(mday_index);+__alarm.time.tm_wday = get_num(wday_index);+__alarm.enabled = 1;+}++static ssize_t alarm_store(struct device *cd, struct device_attribute *attr,const char *buf, size_t count) {+get_alarm_from_usr(buf);+hym8563_rtc_set_alarm(&mClient->dev, &__alarm);+return count;+}++static ssize_t alarm_show(struct device *cd, struct device_attribute *attr, char *buf) {+if(__alarm.enabled)+return sprintf(buf, "alarm is enabled! wday:%d,mday:%d,hour:%d,min:%dn",+__alarm.time.tm_wday, __alarm.time.tm_mday, __alarm.time.tm_hour, __alarm.time.tm_min);+return sprintf(buf, "alarm is disabled!n");+}++static DEVICE_ATTR_RW(alarm);++static ssize_t enable_store(struct device *cd, struct device_attribute *attr,const char *buf, size_t count) {+if(simple_strtoul(buf, NULL, 10)) {+__alarm.enabled = 1;+hym8563_rtc_alarm_irq_enable(&mClient->dev, 1);+}+else {+__alarm.enabled = 0;+hym8563_rtc_alarm_irq_enable(&mClient->dev, 0);+}+return count;+}++static ssize_t enable_show(struct device *cd, struct device_attribute *attr, char *buf) {+return sprintf(buf, "%dn", __alarm.enabled);+}+++static DEVICE_ATTR_RW(enable);++static ssize_t time_show(struct device *cd, struct device_attribute *attr, char *buf) {+struct rtc_time tm;++hym8563_rtc_read_time(&mClient->dev, &tm);+return sprintf(buf,"%d/%d/%d %02d:%02d:%02d wday:%dn",+tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, tm.tm_wday);+}++static ssize_t time_store(struct device *cd, struct device_attribute *attr,const char *buf, size_t count) {+return count;+}+++static DEVICE_ATTR_RW(time);+++static struct attribute *time_ctrl_attrs[] = {+&dev_attr_alarm.attr,+&dev_attr_enable.attr,+&dev_attr_time.attr,+NULL,+};+ATTRIBUTE_GROUPS(time_ctrl);+++static struct class time_ctrl_class = {+.name = "time_ctrl",+.class_groups = time_ctrl_groups,+};++/* * Handling of the clkout */@@ -371,10 +470,12 @@static int hym8563_clkout_prepare(struct clk_hw *hw)return hym8563_clkout_control(hw, 1);}
+/*static void hym8563_clkout_unprepare(struct clk_hw *hw){hym8563_clkout_control(hw, 0);}+*/
static int hym8563_clkout_is_prepared(struct clk_hw *hw){@@ -390,7 +491,7 @@static int hym8563_clkout_is_prepared(struct clk_hw *hw)
static const struct clk_ops hym8563_clkout_ops = {.prepare = hym8563_clkout_prepare,-.unprepare = hym8563_clkout_unprepare,+//.unprepare = hym8563_clkout_unprepare,    //clk always on,mask for fix suspend crash.is_prepared = hym8563_clkout_is_prepared,.recalc_rate = hym8563_clkout_recalc_rate,.round_rate = hym8563_clkout_round_rate,@@ -402,11 +503,16 @@static struct clk *hym8563_clkout_register_clk(struct hym8563 *hym8563)struct i2c_client *client = hym8563->client;struct device_node *node = client->dev.of_node;struct clk *clk;-struct clk_init_data init;+struct clk_init_data init = {};+int ret;++ret = i2c_smbus_write_byte_data(client, HYM8563_CLKOUT,0x80);+if (ret < 0)+return ERR_PTR(ret);
init.name = "hym8563-clkout";init.ops = &hym8563_clkout_ops;-init.flags = CLK_IS_CRITICAL;+init.flags = 0;init.parent_names = NULL;init.num_parents = 0;hym8563->clkout_hw.init = &init;@@ -447,11 +553,7 @@static irqreturn_t hym8563_irq(int irq, void *dev_id)goto out;}
-dev_info(&client->dev, "%s: irq stat 0x%xn", __func__, data);data &= ~HYM8563_CTL2_AF;-/*clean timer irq and reset timer count down*/-data &= ~HYM8563_CTL2_TF;-i2c_smbus_write_byte_data(client, HYM8563_TMR_CNT, 0);
ret = i2c_smbus_write_byte_data(client, HYM8563_CTL2, data);if (ret < 0) {@@ -468,11 +570,6 @@static int hym8563_init_device(struct i2c_client *client){int ret;
-ret = i2c_smbus_read_byte_data(client, HYM8563_CTL1);-if (ret < 0)-dev_err(&client->dev, "%s: error read i2c data %dn",-__func__, ret);-/* Clear stop flag if present */ret = i2c_smbus_write_byte_data(client, HYM8563_CTL1, 0);if (ret < 0)@@ -495,10 +592,6 @@static int hym8563_init_device(struct i2c_client *client)
ret &= ~HYM8563_CTL2_TI_TP;
-/* Reset timer cnt and Set timer countdown 1s per count */-i2c_smbus_write_byte_data(client, HYM8563_TMR_CNT, 0);-i2c_smbus_write_byte_data(client, HYM8563_TMR_CTL, HYM8563_TMR_CFG);-return i2c_smbus_write_byte_data(client, HYM8563_CTL2, ret);}
@@ -522,12 +615,6 @@static int hym8563_suspend(struct device *dev)static int hym8563_resume(struct device *dev){struct i2c_client *client = to_i2c_client(dev);-int ret;--ret = i2c_smbus_read_byte_data(client, HYM8563_CTL1);-if (ret < 0)-dev_err(&client->dev, "%s: error read i2c data %dn",-__func__, ret);
if (device_may_wakeup(dev))disable_irq_wake(client->irq);@@ -542,6 +629,7 @@static int hym8563_probe(struct i2c_client *client){struct hym8563 *hym8563;int ret;+//int valid;/* * hym8563 initial time(2021_1_1_1200), * avoid hym8563 read time error@@ -555,15 +643,12 @@static int hym8563_probe(struct i2c_client *client).tm_min = 0,.tm_sec = 0,};+printk("abc rtcDBG [%s] start n ",__FUNCTION__);
hym8563 = devm_kzalloc(&client->dev, sizeof(*hym8563), GFP_KERNEL);if (!hym8563)return -ENOMEM;
-hym8563->rtc = devm_rtc_allocate_device(&client->dev);-if (IS_ERR(hym8563->rtc))-return PTR_ERR(hym8563->rtc);-hym8563->client = client;i2c_set_clientdata(client, hym8563);
@@ -573,6 +658,7 @@static int hym8563_probe(struct i2c_client *client)return ret;}
+mClient = client;if (client->irq > 0) {ret = devm_request_threaded_irq(&client->dev, client->irq,NULL, hym8563_irq,@@ -603,14 +689,22 @@static int hym8563_probe(struct i2c_client *client)  (tm_read.tm_mon == -1) || (rtc_valid_tm(&tm_read) != 0))hym8563_rtc_set_time(&client->dev, &tm);
-hym8563->rtc->ops = &hym8563_rtc_ops;-clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, hym8563->rtc->features);+hym8563_rtc_alarm_irq_enable(&client->dev, 0);+class_register(&time_ctrl_class);+hym8563->rtc = devm_rtc_device_register(&client->dev, client->name,+&hym8563_rtc_ops, THIS_MODULE);+if (IS_ERR(hym8563->rtc))+return PTR_ERR(hym8563->rtc);++/* the hym8563 alarm only supports a minute accuracy */+//hym8563->rtc->uie_unsupported = 1;
#ifdef CONFIG_COMMON_CLKhym8563_clkout_register_clk(hym8563);#endif
-return devm_rtc_register_device(hym8563->rtc);+printk("abc rtcDBG [%s] end n",__FUNCTION__);+return 0;}
static const struct i2c_device_id hym8563_id[] = {@@ -627,7 +721,7 @@MODULE_DEVICE_TABLE(of, hym8563_dt_idtable);
static struct i2c_driver hym8563_driver = {.driver= {-.name= "rtc-hym8563",+.name= "haoyu,hym8563",.pm= &hym8563_pm_ops,.of_match_table= hym8563_dt_idtable,},

二、Linux系統(tǒng)：RTC自動開機(jī)實(shí)操

1.第一步：同步系統(tǒng)時(shí)間到RTC

首先需要確保系統(tǒng)時(shí)間正確，再將系統(tǒng)時(shí)間寫入RTC芯片（避免RTC時(shí)間錯(cuò)亂導(dǎo)致喚醒失敗）。

打開終端，執(zhí)行以下兩條指令：

??驗(yàn)證：執(zhí)行hwclock -r（read RTC），若輸出時(shí)間與剛才設(shè)置的一致，說明同步成功。

2.第二步：配置RTC喚醒鬧鐘并關(guān)機(jī)

接下來設(shè)置“多久后自動開機(jī)”（這里以「1分鐘后喚醒」為例），然后關(guān)機(jī)等待。

依次執(zhí)行以下三條指令：

??操作后：設(shè)備會立即關(guān)機(jī)，等待約1分鐘，即可看到系統(tǒng)自動開機(jī)。

3.第三步：驗(yàn)證RTC喚醒配置（可選）

若想確認(rèn)喚醒時(shí)間是否設(shè)置成功，可在關(guān)機(jī)前執(zhí)行以下指令查看：

示例輸出（cat /proc/driver/rtc）：

三、Android系統(tǒng)：RTC自動開機(jī)實(shí)操

Android系統(tǒng)的操作邏輯與Linux一致，但部分指令格式和關(guān)機(jī)命令有差異，需注意區(qū)分。

1.第一步：同步系統(tǒng)時(shí)間到RTC

Android的date指令時(shí)間格式為「MMDDhhmmYYYY.ss」（月日時(shí)分年。秒），其他邏輯和Linux相同。

執(zhí)行指令：

??驗(yàn)證：同樣執(zhí)行hwclock -r，確認(rèn)RTC時(shí)間與系統(tǒng)時(shí)間一致。

2.第二步：配置RTC喚醒鬧鐘并關(guān)機(jī)

Android關(guān)機(jī)指令需用reboot -p（power off），其他喚醒配置指令與Linux完全相同：

??操作后：設(shè)備關(guān)機(jī)，等待1分鐘左右自動開機(jī)，效果與Linux一致。

3.第三步：驗(yàn)證配置（與Linux相同）

四、常見問題排查：設(shè)置后不自動開機(jī)？

如果按步驟操作后設(shè)備未自動喚醒，可從以下4個(gè)維度排查：

1.檢查RTC驅(qū)動是否正常加載

首先確認(rèn)RTC驅(qū)動已加載，以HYM8563為例：

2.確認(rèn)RTC節(jié)點(diǎn)路徑是否正確

部分設(shè)備的RTC節(jié)點(diǎn)可能不是rtc0（如rtc1），需先查看實(shí)際節(jié)點(diǎn)：

3.檢查RTC備用電池是否正常

RTC芯片在設(shè)備關(guān)機(jī)后需靠備用電池（如紐扣電池）供電，若電池沒電或接觸不良，RTC會停止計(jì)時(shí)，自然無法喚醒。

??排查：開機(jī)后執(zhí)行hwclock -r，若時(shí)間顯示為“1970年”或錯(cuò)亂，說明RTC電池沒電，需更換電池。

4.確認(rèn)喚醒時(shí)間格式是否正確

?避免直接寫“HHSS”（如echo 1100 > ...），需用「時(shí)間戳」或「+秒數(shù)」格式；

?若指定具體時(shí)間，需先計(jì)算時(shí)間戳：date -d "20241023 1100" +%s，再將結(jié)果寫入wakealarm。

五、總結(jié)

RTC自動開機(jī)是嵌入式系統(tǒng)中非常實(shí)用的功能，核心是通過sysfs接口操作RTC喚醒鬧鐘，步驟可歸納為：

1.同步系統(tǒng)時(shí)間到RTC（確保時(shí)間基準(zhǔn)正確）；

2.清空歷史喚醒配置，設(shè)置新喚醒時(shí)間；

3.執(zhí)行關(guān)機(jī)指令，等待RTC觸發(fā)開機(jī)。

無論是Linux還是Android，操作邏輯一致，僅需注意指令格式和關(guān)機(jī)命令的差異。如果你的設(shè)備使用其他RTC芯片（如DS3231、PCF8563），操作步驟也基本相同，只需確保驅(qū)動支持喚醒功能即可。

快去你的嵌入式設(shè)備上試試吧！如果遇到問題，歡迎在評論區(qū)留言討論～