linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 * Real Time Clock (RTC) Driver for sd3078

 * Copyright (C) 2018 Zoro Li

 */

​

#include <linux/bcd.h>

#include <linux/i2c.h>

#include <linux/module.h>

#include <linux/regmap.h>

#include <linux/rtc.h>

#include <linux/slab.h>

​

#define SD3078_REG_SC           0x00

#define SD3078_REG_MN           0x01

#define SD3078_REG_HR           0x02

#define SD3078_REG_DW           0x03

#define SD3078_REG_DM           0x04

#define SD3078_REG_MO           0x05

#define SD3078_REG_YR           0x06

​

#define SD3078_REG_CTRL1        0x0f

#define SD3078_REG_CTRL2        0x10

#define SD3078_REG_CTRL3        0x11

​

#define KEY_WRITE1      0x80

#define KEY_WRITE2      0x04

#define KEY_WRITE3      0x80

​

#define NUM_TIME_REGS   (SD3078_REG_YR - SD3078_REG_SC + 1)

​

/*

 * The sd3078 has write protection

 * and we can choose whether or not to use it.

 * Write protection is turned off by default.

 */

#define WRITE_PROTECT_EN    0

​

struct sd3078 {

    struct rtc_device   *rtc;

    struct regmap       *regmap;

};

​

/*

 * In order to prevent arbitrary modification of the time register,

 * when modification of the register,

 * the "write" bit needs to be written in a certain order.

 * 1. set WRITE1 bit

 * 2. set WRITE2 bit

 * 3. set WRITE3 bit

 */

static void sd3078_enable_reg_write(struct sd3078 *sd3078)

{

    regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,

               KEY_WRITE1, KEY_WRITE1);

    regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,

               KEY_WRITE2, KEY_WRITE2);

    regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,

               KEY_WRITE3, KEY_WRITE3);

}

​

#if WRITE_PROTECT_EN

/*

 * In order to prevent arbitrary modification of the time register,

 * we should disable the write function.

 * when disable write,

 * the "write" bit needs to be clear in a certain order.

 * 1. clear WRITE2 bit

 * 2. clear WRITE3 bit

 * 3. clear WRITE1 bit

 */

static void sd3078_disable_reg_write(struct sd3078 *sd3078)

{

    regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,

               KEY_WRITE2, 0);

    regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,

               KEY_WRITE3, 0);

    regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,

               KEY_WRITE1, 0);

}

#endif

​

static int sd3078_rtc_read_time(struct device *dev, struct rtc_time *tm)

{

    unsigned char hour;

    unsigned char rtc_data[NUM_TIME_REGS] = {0};

    struct i2c_client *client = to_i2c_client(dev);

    struct sd3078 *sd3078 = i2c_get_clientdata(client);

    int ret;

​

    ret = regmap_bulk_read(sd3078->regmap, SD3078_REG_SC, rtc_data,

                   NUM_TIME_REGS);