RK3568 RTC 驱动开发详解
实时时钟（RTC）是嵌入式系统中不可或缺的硬件模块，负责在系统断电后继续计时，为设备提供稳定的时间基准。本文将以瑞芯微 RK3568 平台为例，详细介绍 RTC 驱动的开发过程，包括子系统架构、设备树配置、驱动实现及测试方法。
一、Linux RTC 子系统架构
Linux 内核通过 RTC 子系统实现对各类 RTC 硬件的统一管理，其架构采用分层设计：
┌─────────────────────────────────────────┐
│ 用户空间 │
│ ┌──────────┐ ┌──────────┐ ┌────────┐ │
│ │ hwclock │ │ date │ │ 应用程序│ │
│ └──────────┘ └──────────┘ └────────┘ │
└───────────────────┬─────────────────────┘
│
┌───────────────────▼─────────────────────┐
│ 内核空间 │
│ ┌───────────────────────────────────┐ │
│ │ RTC核心层 │ │
│ │ (rtc_class_ops .c) │ │
│ └───────────────────┬───────────────┘ │
│ │ │
│ ┌───────────────────▼───────────────┐ │
│ │ RTC驱动层 │ │
│ │ (rtc-rx8010.c 具体实现) │ │
│ └───────────────────┬───────────────┘ │
└──────────────────────┼──────────────────┘
│
┌──────────────────────▼──────────────────┐
│ 硬件层 │
│ RK3568 RTC控制器 + 晶体振荡器 │
└─────────────────────────────────────────┘
- 核心层： 提供统一的用户空间接口（字符设备/dev/rtc0）和驱动框架，定义标准操作集
- 驱动层： 实现具体硬件的操作，对接 RTC 核心层的抽象接口
- 用户空间： 通过ioctl、read等系统调用访问 RTC 功能，或使用hwclock等工具
核心数据结构：
// RTC操作函数集
struct rtc_class_ops {
int (*read_time)(struct device *dev, struct rtc_time *tm); // 读时间
int (*set_time)(struct device *dev, struct rtc_time *tm); // 设时间
int (*read_alarm)(struct device *dev, struct rtc_wkalrm *alrm); // 读闹钟
int (*set_alarm)(struct device *dev, struct rtc_wkalrm *alrm); // 设闹钟
int (*proc)(struct device *dev, struct seq_file *seq); // 调试信息
// 其他操作...
};
二、设备树配置
RK3568外挂RTC硬件原理图：
定义rtc设备节点：
kernel/arch/arm64/boot/dts/rockchip/rk3568-evb1-ddr4-v10.dtsi
&i2c5 {
status = "okay";
rx8010: rx8010@32 {
compatible = "epson,rx8010";
reg = <0x32>;
status = "okay";
#clock-cells = <0>;
};
};
i2c5设备节点描述如下：
kernel/arch/arm64/boot/dts/rockchip/rk3568.dtsi
引脚复用定义在kernel/arch/arm64/boot/dts/rockchip/rk3568-pinctrl.dtsi
三、驱动
因为RK809带有RTC功能，使用外挂RTC时需要先禁用，具体操作如下：
执行make menuconfig
Device Drivers --->
[*] Real Time Clock --->
<> Rockchip RK805/RK808/RK809/RK816/RK817/RK818 RTC
<*> Epson RX8010SJ
取消Rockchip RK805/RK808/RK809/RK816/RK817/RK818 RTC选中
选中Epson RX8010SJ
驱动代码：kernel/drivers/rtc/rtc-rx8010.c
/*
* Driver for the Epson RTC module RX-8010 SJ
*
* Copyright(C) Timesys Corporation 2015
* Copyright(C) General Electric Company 2015
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/bcd.h>
#include <linux/bitops.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/rtc.h>
#define RX8010_SEC 0x10
#define RX8010_MIN 0x11
#define RX8010_HOUR 0x12
#define RX8010_WDAY 0x13
#define RX8010_MDAY 0x14
#define RX8010_MONTH 0x15
#define RX8010_YEAR 0x16
#define RX8010_RESV17 0x17
#define RX8010_ALMIN 0x18
#define RX8010_ALHOUR 0x19
#define RX8010_ALWDAY 0x1A
#define RX8010_TCOUNT0 0x1B
#define RX8010_TCOUNT1 0x1C
#define RX8010_EXT 0x1D
#define RX8010_FLAG 0x1E
#define RX8010_CTRL 0x1F
/* 0x20 to 0x2F are user registers */
#define RX8010_RESV30 0x30
#define RX8010_RESV31 0x31
#define RX8010_IRQ 0x32
#define RX8010_EXT_WADA BIT(3)
#define RX8010_FLAG_VLF BIT(1)
#define RX8010_FLAG_AF BIT(3)
#define RX8010_FLAG_TF BIT(4)
#define RX8010_FLAG_UF BIT(5)
#define RX8010_CTRL_AIE BIT(3)
#define RX8010_CTRL_UIE BIT(5)
#define RX8010_CTRL_STOP BIT(6)
#define RX8010_CTRL_TEST BIT(7)
#define RX8010_ALARM_AE BIT(7)
static const struct i2c_device_id rx8010_id[] = {
{ "rx8010", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, rx8010_id);
static const struct of_device_id rx8010_of_match[] = {
{ .compatible = "epson,rx8010" },
{ }
};
MODULE_DEVICE_TABLE(of, rx8010_of_match);
struct rx8010_data {
struct i2c_client *client;
struct rtc_device *rtc;
u8 ctrlreg;
};
static irqreturn_t rx8010_irq_1_handler(int irq, void *dev_id)
{
struct i2c_client *client = dev_id;
struct rx8010_data *rx8010 = i2c_get_clientdata(client);
int flagreg;
mutex_lock(&rx8010->rtc->ops_lock);
flagreg = i2c_smbus_read_byte_data(client, RX8010_FLAG);
if (flagreg <= 0) {
mutex_unlock(&rx8010->rtc->ops_lock);
return IRQ_NONE;
}
if (flagreg & RX8010_FLAG_VLF)
dev_warn(&client->dev, "Frequency stop detected\n");
if (flagreg & RX8010_FLAG_TF) {
flagreg &= ~RX8010_FLAG_TF;
rtc_update_irq(rx8010->rtc, 1, RTC_PF | RTC_IRQF);
}
if (flagreg & RX8010_FLAG_AF) {
flagreg &= ~RX8010_FLAG_AF;
rtc_update_irq(rx8010->rtc, 1, RTC_AF | RTC_IRQF);
}
if (flagreg & RX8010_FLAG_UF) {
flagreg &= ~RX8010_FLAG_UF;
rtc_update_irq(rx8010->rtc, 1, RTC_UF | RTC_IRQF);
}
i2c_smbus_write_byte_data(client, RX8010_FLAG, flagreg);
mutex_unlock(&rx8010->rtc->ops_lock);
return IRQ_HANDLED;
}
static int rx8010_get_time(struct device *dev, struct rtc_time *dt)
{
struct rx8010_data *rx8010 = dev_get_drvdata(dev);
u8 date[7];
int flagreg;
int err;
flagreg = i2c_smbus_read_byte_data(rx8010->client, RX8010_FLAG);
if (flagreg < 0)
return flagreg;
if (flagreg & RX8010_FLAG_VLF) {
dev_warn(dev, "Frequency stop detected\n");
return -EINVAL;
}
err = i2c_smbus_read_i2c_block_data(rx8010->client, RX8010_SEC,
7, date);
if (err != 7)
return err < 0 ? err : -EIO;
dt->tm_sec = bcd2bin(date[RX8010_SEC - RX8010_SEC] & 0x7f);
dt->tm_min = bcd2bin(date[RX8010_MIN - RX8010_SEC] & 0x7f);
dt->tm_hour = bcd2bin(date[RX8010_HOUR - RX8010_SEC] & 0x3f);
dt->tm_mday = bcd2bin(date[RX8010_MDAY - RX8010_SEC] & 0x3f);
dt->tm_mon = bcd2bin(date[RX8010_MONTH - RX8010_SEC] & 0x1f) - 1;
dt->tm_year = bcd2bin(date[RX8010_YEAR - RX8010_SEC]) + 100;
dt->tm_wday = ffs(date[RX8010_WDAY - RX8010_SEC] & 0x7f);
return 0;
}
static int rx8010_set_time(struct device *dev, struct rtc_time *dt)
{
struct rx8010_data *rx8010 = dev_get_drvdata(dev);
u8 date[7];
int ctrl, flagreg;
int ret;
if ((dt->tm_year < 100) || (dt->tm_year > 199))
return -EINVAL;
/* set STOP bit before changing clock/calendar */
ctrl = i2c_smbus_read_byte_data(rx8010->client, RX8010_CTRL);
if (ctrl < 0)
return ctrl;
rx8010->ctrlreg = ctrl | RX8010_CTRL_STOP;
ret = i2c_smbus_write_byte_data(rx8010->client, RX8010_CTRL,
rx8010->ctrlreg);
if (ret < 0)
return ret;
date[RX8010_SEC - RX8010_SEC] = bin2bcd(dt->tm_sec);
date[RX8010_MIN - RX8010_SEC] = bin2bcd(dt->tm_min);
date[RX8010_HOUR - RX8010_SEC] = bin2bcd(dt->tm_hour);
date[RX8010_MDAY - RX8010_SEC] = bin2bcd(dt->tm_mday);
date[RX8010_MONTH - RX8010_SEC] = bin2bcd(dt->tm_mon + 1);
date[RX8010_YEAR - RX8010_SEC] = bin2bcd(dt->tm_year - 100);
date[RX8010_WDAY - RX8010_SEC] = bin2bcd(1 << dt->tm_wday);
ret = i2c_smbus_write_i2c_block_data(rx8010->client,
RX8010_SEC, 7, date);
if (ret < 0)
return ret;
/* clear STOP bit after changing clock/calendar */
ctrl = i2c_smbus_read_byte_data(rx8010->client, RX8010_CTRL);
if (ctrl < 0)
return ctrl;
rx8010->ctrlreg = ctrl & ~RX8010_CTRL_STOP;
ret = i2c_smbus_write_byte_data(rx8010->client, RX8010_CTRL,
rx8010->ctrlreg);
if (ret < 0)
return ret;
flagreg = i2c_smbus_read_byte_data(rx8010->client, RX8010_FLAG);
if (flagreg < 0) {
return flagreg;
}
if (flagreg & RX8010_FLAG_VLF)
ret = i2c_smbus_write_byte_data(rx8010->client, RX8010_FLAG,
flagreg & ~RX8010_FLAG_VLF);
return 0;
}
static int rx8010_init_client(struct i2c_client *client)
{
struct rx8010_data *rx8010 = i2c_get_clientdata(client);
u8 ctrl[2];
int need_clear = 0, err = 0;
/* add by lgq 2021-12-17 */
u8 flag;
flag = i2c_smbus_read_byte_data(client, RX8010_FLAG);
if(err < 0)
return err;
flag &= ~(RX8010_FLAG_VLF);
err = i2c_smbus_write_byte_data(client, RX8010_FLAG, flag);
/* end add */
/* Initialize reserved registers as specified in datasheet */
err = i2c_smbus_write_byte_data(client, RX8010_RESV17, 0xD8);
if (err < 0)
return err;
err = i2c_smbus_write_byte_data(client, RX8010_RESV30, 0x00);
if (err < 0)
return err;
err = i2c_smbus_write_byte_data(client, RX8010_RESV31, 0x08);
if (err < 0)
return err;
err = i2c_smbus_write_byte_data(client, RX8010_IRQ, 0x00);
if (err < 0)
return err;
err = i2c_smbus_read_i2c_block_data(rx8010->client, RX8010_FLAG,
2, ctrl);
if (err != 2)
return err < 0 ? err : -EIO;
if (ctrl[0] & RX8010_FLAG_VLF)
dev_warn(&client->dev, "Frequency stop was detected\n");
if (ctrl[0] & RX8010_FLAG_AF) {
dev_warn(&client->dev, "Alarm was detected\n");
need_clear = 1;
}
if (ctrl[0] & RX8010_FLAG_TF)
need_clear = 1;
if (ctrl[0] & RX8010_FLAG_UF)
need_clear = 1;
if (need_clear) {
ctrl[0] &= ~(RX8010_FLAG_AF | RX8010_FLAG_TF | RX8010_FLAG_UF);
err = i2c_smbus_write_byte_data(client, RX8010_FLAG, ctrl[0]);
if (err < 0)
return err;
}
rx8010->ctrlreg = (ctrl[1] & ~RX8010_CTRL_TEST);
return 0;
}
static int rx8010_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
struct rx8010_data *rx8010 = dev_get_drvdata(dev);
struct i2c_client *client = rx8010->client;
u8 alarmvals[3];
int flagreg;
int err;
err = i2c_smbus_read_i2c_block_data(client, RX8010_ALMIN, 3, alarmvals);
if (err != 3)
return err < 0 ? err : -EIO;
flagreg = i2c_smbus_read_byte_data(client, RX8010_FLAG);
if (flagreg < 0)
return flagreg;
t->time.tm_sec = 0;
t->time.tm_min = bcd2bin(alarmvals[0] & 0x7f);
t->time.tm_hour = bcd2bin(alarmvals[1] & 0x3f);
if (!(alarmvals[2] & RX8010_ALARM_AE))
t->time.tm_mday = bcd2bin(alarmvals[2] & 0x7f);
t->enabled = !!(rx8010->ctrlreg & RX8010_CTRL_AIE);
t->pending = (flagreg & RX8010_FLAG_AF) && t->enabled;
return 0;
}
static int rx8010_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
struct i2c_client *client = to_i2c_client(dev);
struct rx8010_data *rx8010 = dev_get_drvdata(dev);
u8 alarmvals[3];
int extreg, flagreg;
int err;
flagreg = i2c_smbus_read_byte_data(client, RX8010_FLAG);
if (flagreg < 0) {
return flagreg;
}
if (rx8010->ctrlreg & (RX8010_CTRL_AIE | RX8010_CTRL_UIE)) {
rx8010->ctrlreg &= ~(RX8010_CTRL_AIE | RX8010_CTRL_UIE);
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_CTRL,
rx8010->ctrlreg);
if (err < 0) {
return err;
}
}
flagreg &= ~RX8010_FLAG_AF;
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_FLAG, flagreg);
if (err < 0)
return err;
alarmvals[0] = bin2bcd(t->time.tm_min);
alarmvals[1] = bin2bcd(t->time.tm_hour);
alarmvals[2] = bin2bcd(t->time.tm_mday);
err = i2c_smbus_write_i2c_block_data(rx8010->client, RX8010_ALMIN,
2, alarmvals);
if (err < 0)
return err;
extreg = i2c_smbus_read_byte_data(client, RX8010_EXT);
if (extreg < 0)
return extreg;
extreg |= RX8010_EXT_WADA;
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_EXT, extreg);
if (err < 0)
return err;
if (alarmvals[2] == 0)
alarmvals[2] |= RX8010_ALARM_AE;
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_ALWDAY,
alarmvals[2]);
if (err < 0)
return err;
if (t->enabled) {
if (rx8010->rtc->uie_rtctimer.enabled)
rx8010->ctrlreg |= RX8010_CTRL_UIE;
if (rx8010->rtc->aie_timer.enabled)
rx8010->ctrlreg |=
(RX8010_CTRL_AIE | RX8010_CTRL_UIE);
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_CTRL,
rx8010->ctrlreg);
if (err < 0)
return err;
}
return 0;
}
static int rx8010_alarm_irq_enable(struct device *dev,
unsigned int enabled)
{
struct i2c_client *client = to_i2c_client(dev);
struct rx8010_data *rx8010 = dev_get_drvdata(dev);
int flagreg;
u8 ctrl;
int err;
ctrl = rx8010->ctrlreg;
if (enabled) {
if (rx8010->rtc->uie_rtctimer.enabled)
ctrl |= RX8010_CTRL_UIE;
if (rx8010->rtc->aie_timer.enabled)
ctrl |= (RX8010_CTRL_AIE | RX8010_CTRL_UIE);
} else {
if (!rx8010->rtc->uie_rtctimer.enabled)
ctrl &= ~RX8010_CTRL_UIE;
if (!rx8010->rtc->aie_timer.enabled)
ctrl &= ~RX8010_CTRL_AIE;
}
flagreg = i2c_smbus_read_byte_data(client, RX8010_FLAG);
if (flagreg < 0)
return flagreg;
flagreg &= ~RX8010_FLAG_AF;
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_FLAG, flagreg);
if (err < 0)
return err;
if (ctrl != rx8010->ctrlreg) {
rx8010->ctrlreg = ctrl;
err = i2c_smbus_write_byte_data(rx8010->client, RX8010_CTRL,
rx8010->ctrlreg);
if (err < 0)
return err;
}
return 0;
}
static int rx8010_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
struct i2c_client *client = to_i2c_client(dev);
struct rx8010_data *rx8010 = dev_get_drvdata(dev);
int ret, tmp;
int flagreg;
switch (cmd) {
case RTC_VL_READ:
flagreg = i2c_smbus_read_byte_data(rx8010->client, RX8010_FLAG);
if (flagreg < 0)
return flagreg;
tmp = !!(flagreg & RX8010_FLAG_VLF);
if (copy_to_user((void __user *)arg, &tmp, sizeof(int)))
return -EFAULT;
return 0;
case RTC_VL_CLR:
flagreg = i2c_smbus_read_byte_data(rx8010->client, RX8010_FLAG);
if (flagreg < 0) {
return flagreg;
}
flagreg &= ~RX8010_FLAG_VLF;
ret = i2c_smbus_write_byte_data(client, RX8010_FLAG, flagreg);
if (ret < 0)
return ret;
return 0;
default:
return -ENOIOCTLCMD;
}
}
static const struct rtc_class_ops rx8010_rtc_ops_default = {
.read_time = rx8010_get_time,
.set_time = rx8010_set_time,
.ioctl = rx8010_ioctl,
};
static const struct rtc_class_ops rx8010_rtc_ops_alarm = {
.read_time = rx8010_get_time,
.set_time = rx8010_set_time,
.ioctl = rx8010_ioctl,
.read_alarm = rx8010_read_alarm,
.set_alarm = rx8010_set_alarm,
.alarm_irq_enable = rx8010_alarm_irq_enable,
};
static int rx8010_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
const struct rtc_class_ops *rtc_ops;
struct rx8010_data *rx8010;
int err = 0;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA
| I2C_FUNC_SMBUS_I2C_BLOCK)) {
dev_err(&adapter->dev, "doesn't support required functionality\n");
return -EIO;
}
rx8010 = devm_kzalloc(&client->dev, sizeof(struct rx8010_data),
GFP_KERNEL);
if (!rx8010)
return -ENOMEM;
rx8010->client = client;
i2c_set_clientdata(client, rx8010);
err = rx8010_init_client(client);
if (err)
return err;
if (client->irq > 0) {
dev_info(&client->dev, "IRQ %d supplied\n", client->irq);
err = devm_request_threaded_irq(&client->dev, client->irq, NULL,
rx8010_irq_1_handler,
IRQF_TRIGGER_LOW | IRQF_ONESHOT,
"rx8010", client);
if (err) {
dev_err(&client->dev, "unable to request IRQ\n");
return err;
}
rtc_ops = &rx8010_rtc_ops_alarm;
} else {
rtc_ops = &rx8010_rtc_ops_default;
}
rx8010->rtc = devm_rtc_device_register(&client->dev, client->name,
rtc_ops, THIS_MODULE);
if (IS_ERR(rx8010->rtc)) {
dev_err(&client->dev, "unable to register the class device\n");
return PTR_ERR(rx8010->rtc);
}
rx8010->rtc->max_user_freq = 1;
return err;
}
static struct i2c_driver rx8010_driver = {
.driver = {
.name = "rtc-rx8010",
.of_match_table = of_match_ptr(rx8010_of_match),
},
.probe = rx8010_probe,
.id_table = rx8010_id,
};
module_i2c_driver(rx8010_driver);
MODULE_AUTHOR("Akshay Bhat <akshay.bhat@timesys.com>");
MODULE_DESCRIPTION("Epson RX8010SJ RTC driver");
MODULE_LICENSE("GPL v2");
四、时间相关命令
linux有2个时间，一个是系统时间，一个是rtc时间，命令如下：
date #系统时间
date +"%Y:%m:%d" #格式化输出系统时间
hwclock #rtc时间
hwclock -w #将系统时间同步到硬件
hwclock -s #将硬件时间同步到系统
