RTC驱动调试

本文记录之前做驱动移植工作时调试RTC的一些总结,Platform: RK3368    OS: Android 7.1  RTC:hym8563

 

RTC核心文件
/drivers/rtc/class.c 该文件向linux设备模型核心注册了一个类RTC,然后向驱动程序提供了注册/注销接口
/drivers/rtc/rtc-dev.c 定义了基本的设备文件操作函数,如:open, read 等
/drivers/rtc/interface.c 主要提供了用户程序与RTC驱动的接口函数,用户程序一般通过ioctl与RTC 驱动交互,这里定义了每个ioctl命令需要调用的函数
/drivers/rtc/rtc-sysfs.c 与sysfs有关
/drivers/rtc/rtc-proc.c 与proc文件系统有关
/include/linux/rtc.h

定义了与RTC有关的数据结构

 

 

 

 

 

 

设备地址及配置:

模块 hym8563,总线地址: 1010 001 R/W

右移一位得:0101 0001 —> reg = <0x51>

dts 配置

hym8563@51 {
        compatible = "haoyu,hym8563";
        reg = <0x51>;
        #clock-cells = <0>;
};

板子上的设备路径 /sys/bus/i2c/devices/3-0051

class 设备节点 /sys/class/rtc/rtc0

rockchip:/sys/class/rtc/rtc0 $ ls
date device  max_user_freq power       subsystem uevent    
dev  hctosys name          since_epoch time      wakealarm

rockchip:/sys/class/rtc/rtc0 $ cat time
11:33:54
rockchip:/sys/class/rtc/rtc0 $ cat date
2019-01-16
rockchip:/sys/class/rtc/rtc0 $ cat name
hym8563
rockchip:/sys/class/rtc/rtc0 $ cat max_user_freq                              
64
rockchip:/sys/class/rtc/rtc0 $ cat uevent                                     
MAJOR=253
MINOR=0
DEVNAME=rtc0

驱动路径 /sys/bus/i2c/drivers/rtc-hym8563/3-0051

注册成功;

测试rtc模块的 i2c总线时钟, 输入 hwclock -w 回车检测时钟引脚的波形变化

 RTC驱动代码分析:

 断电之后上电时RTC的系统时间设置函数位于 drivers/rtc/hctosys.c

/*                                                                                                                                             
 * RTC subsystem, initialize system time on startup
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include 
static int __init rtc_hctosys(void)
{
    int err = -ENODEV;
    struct rtc_time tm;
    struct timespec64 tv64 = {
        .tv_nsec = NSEC_PER_SEC >> 1,
    };
    struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);

    if (rtc == NULL) {
        pr_info("unable to open rtc device (%s)\n",
            CONFIG_RTC_HCTOSYS_DEVICE);
        goto err_open;
    }
    err = rtc_read_time(rtc, &tm);
    if (err) {
        dev_err(rtc->dev.parent,
            "hctosys: unable to read the hardware clock\n");
        goto err_read;
    }

    tv64.tv_sec = rtc_tm_to_time64(&tm);
    err = do_settimeofday64(&tv64);
/*
 *  上电启动内核时打印 RTC 系统时间设置情况
*/
    dev_info(rtc->dev.parent,
        "setting system clock to "
        "%d-%02d-%02d %02d:%02d:%02d UTC (%lld)\n",
        tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
        tm.tm_hour, tm.tm_min, tm.tm_sec,
        (long long) tv64.tv_sec);

err_read:
    rtc_class_close(rtc);
err_open:
    rtc_hctosys_ret = err;

    return err;
}
late_initcall(rtc_hctosys);                             

执行上面函数在内核中打印的信息如下:

rockchip:/ $ dmesg | grep rtc                                                 
[    1.086439] rtc-hym8563 3-0051: rtc core: registered hym8563 as rtc0
[    2.150024] rtc-hym8563 3-0051: setting system clock to 2019-01-16 11:18:42 UTC (1547637522)
// 在给设备上电时,首先将系统时间设定为 2019-01-16 11:18:42 UTC
// 然后由系统运行 RTC
rockchip:/ $ date
Wed Jan 16 11:19:13 GMT 2019

i2c 总线初始化设备函数位于  drivers/rtc/rtc-hym8563.c

static int hym8563_init_device(struct i2c_client *client)
{
    int ret;

    /* Clear stop flag if present */
    ret = i2c_smbus_write_byte_data(client, HYM8563_CTL1, 0);  // 写入控制寄存器 0
    if (ret < 0)
        return ret;

    ret = i2c_smbus_read_byte_data(client, HYM8563_CTL2);   //读取状态寄存器,返回0初始化成功
    if (ret < 0)
        return ret;

    /* Disable alarm and timer interrupts */
    ret &= ~HYM8563_CTL2_AIE;
    ret &= ~HYM8563_CTL2_TIE;

    /* Clear any pending alarm and timer flags */
    if (ret & HYM8563_CTL2_AF)
        ret &= ~HYM8563_CTL2_AF;

    if (ret & HYM8563_CTL2_TF)
        ret &= ~HYM8563_CTL2_TF;

    ret &= ~HYM8563_CTL2_TI_TP;
    return i2c_smbus_write_byte_data(client, HYM8563_CTL2, ret);
} 

对上层提供接口: /dev/rtc0

 

参考文章:

rtc 晶振不起振问题:

https://www.cnblogs.com/Pual623548198/p/6683934.html

https://blog.csdn.net/u010278579/article/details/47303297?utm_source=blogxgwz1

https://blog.csdn.net/weiwei_xiaoyu/article/details/82819864

RTC时钟驱动:https://www.cnblogs.com/wanghuaijun/p/7189733.html

RTC相关寄存器: http://tech.hqew.com/fangan_1852073

设备树配置:https://www.cnblogs.com/fah936861121/articles/6908230.html 

 https://www.cnblogs.com/lifexy/p/7839625.html

 

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