/* * rtc class driver for the Maxim MAX6900 chip * * Author: Dale Farnsworth <dale@farnsworth.org> * * based on previously existing rtc class drivers * * 2007 (c) MontaVista, Software, Inc. This file is licensed under * the terms of the GNU General Public License version 2. This program * is licensed "as is" without any warranty of any kind, whether express * or implied. */ #include <linux/module.h> #include <linux/i2c.h> #include <linux/bcd.h> #include <linux/rtc.h> #include <linux/delay.h> #define DRV_NAME "max6900" #define DRV_VERSION "0.1" /* * register indices */ #define MAX6900_REG_SC 0 /* seconds 00-59 */ #define MAX6900_REG_MN 1 /* minutes 00-59 */ #define MAX6900_REG_HR 2 /* hours 00-23 */ #define MAX6900_REG_DT 3 /* day of month 00-31 */ #define MAX6900_REG_MO 4 /* month 01-12 */ #define MAX6900_REG_DW 5 /* day of week 1-7 */ #define MAX6900_REG_YR 6 /* year 00-99 */ #define MAX6900_REG_CT 7 /* control */ /* register 8 is undocumented */ #define MAX6900_REG_CENTURY 9 /* century */ #define MAX6900_REG_LEN 10 #define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */ #define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */ /* * register read/write commands */ #define MAX6900_REG_CONTROL_WRITE 0x8e #define MAX6900_REG_CENTURY_WRITE 0x92 #define MAX6900_REG_CENTURY_READ 0x93 #define MAX6900_REG_RESERVED_READ 0x96 #define MAX6900_REG_BURST_WRITE 0xbe #define MAX6900_REG_BURST_READ 0xbf #define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */ #define MAX6900_I2C_ADDR 0xa0 static const unsigned short normal_i2c[] = { MAX6900_I2C_ADDR >> 1, I2C_CLIENT_END }; I2C_CLIENT_INSMOD; /* defines addr_data */ static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind); static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf) { u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ }; u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ }; struct i2c_msg msgs[4] = { { .addr = client->addr, .flags = 0, /* write */ .len = sizeof(reg_burst_read), .buf = reg_burst_read }, { .addr = client->addr, .flags = I2C_M_RD, .len = MAX6900_BURST_LEN, .buf = buf }, { .addr = client->addr, .flags = 0, /* write */ .len = sizeof(reg_century_read), .buf = reg_century_read }, { .addr = client->addr, .flags = I2C_M_RD, .len = sizeof(buf[MAX6900_REG_CENTURY]), .buf = &buf[MAX6900_REG_CENTURY] } }; int rc; rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); if (rc != ARRAY_SIZE(msgs)) { dev_err(&client->dev, "%s: register read failed\n", __func__); return -EIO; } return 0; } static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf) { u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE }; struct i2c_msg century_msgs[1] = { { .addr = client->addr, .flags = 0, /* write */ .len = sizeof(i2c_century_buf), .buf = i2c_century_buf } }; u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE }; struct i2c_msg burst_msgs[1] = { { .addr = client->addr, .flags = 0, /* write */ .len = sizeof(i2c_burst_buf), .buf = i2c_burst_buf } }; int rc; /* * We have to make separate calls to i2c_transfer because of * the need to delay after each write to the chip. Also, * we write the century byte first, since we set the write-protect * bit as part of the burst write. */ i2c_century_buf[1] = buf[MAX6900_REG_CENTURY]; rc = i2c_transfer(client->adapter, century_msgs, ARRAY_SIZE(century_msgs)); if (rc != ARRAY_SIZE(century_msgs)) goto write_failed; msleep(MAX6900_IDLE_TIME_AFTER_WRITE); memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN); rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs)); if (rc != ARRAY_SIZE(burst_msgs)) goto write_failed; msleep(MAX6900_IDLE_TIME_AFTER_WRITE); return 0; write_failed: dev_err(&client->dev, "%s: register write failed\n", __func__); return -EIO; } static int max6900_i2c_validate_client(struct i2c_client *client) { u8 regs[MAX6900_REG_LEN]; u8 zero_mask[] = { 0x80, /* seconds */ 0x80, /* minutes */ 0x40, /* hours */ 0xc0, /* day of month */ 0xe0, /* month */ 0xf8, /* day of week */ 0x00, /* year */ 0x7f, /* control */ }; int i; int rc; int reserved; reserved = i2c_smbus_read_byte_data(client, MAX6900_REG_RESERVED_READ); if (reserved != 0x07) return -ENODEV; rc = max6900_i2c_read_regs(client, regs); if (rc < 0) return rc; for (i = 0; i < ARRAY_SIZE(zero_mask); ++i) { if (regs[i] & zero_mask[i]) return -ENODEV; } return 0; } static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm) { int rc; u8 regs[MAX6900_REG_LEN]; rc = max6900_i2c_read_regs(client, regs); if (rc < 0) return rc; tm->tm_sec = BCD2BIN(regs[MAX6900_REG_SC]); tm->tm_min = BCD2BIN(regs[MAX6900_REG_MN]); tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f); tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]); tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1; tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) + BCD2BIN(regs[MAX6900_REG_CENTURY]) * 100 - 1900; tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]); return 0; } static int max6900_i2c_clear_write_protect(struct i2c_client *client) { int rc; rc = i2c_smbus_write_byte_data (client, MAX6900_REG_CONTROL_WRITE, 0); if (rc < 0) { dev_err(&client->dev, "%s: control register write failed\n", __func__); return -EIO; } return 0; } static int max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm) { u8 regs[MAX6900_REG_LEN]; int rc; rc = max6900_i2c_clear_write_protect(client); if (rc < 0) return rc; regs[MAX6900_REG_SC] = BIN2BCD(tm->tm_sec); regs[MAX6900_REG_MN] = BIN2BCD(tm->tm_min); regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour); regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday); regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1); regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday); regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year % 100); regs[MAX6900_REG_CENTURY] = BIN2BCD((tm->tm_year + 1900) / 100); /* set write protect */ regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; rc = max6900_i2c_write_regs(client, regs); if (rc < 0) return rc; return 0; } static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm) { return max6900_i2c_read_time(to_i2c_client(dev), tm); } static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) { return max6900_i2c_set_time(to_i2c_client(dev), tm); } static int max6900_attach_adapter(struct i2c_adapter *adapter) { return i2c_probe(adapter, &addr_data, max6900_probe); } static int max6900_detach_client(struct i2c_client *client) { struct rtc_device *const rtc = i2c_get_clientdata(client); if (rtc) rtc_device_unregister(rtc); return i2c_detach_client(client); } static struct i2c_driver max6900_driver = { .driver = { .name = DRV_NAME, }, .id = I2C_DRIVERID_MAX6900, .attach_adapter = max6900_attach_adapter, .detach_client = max6900_detach_client, }; static const struct rtc_class_ops max6900_rtc_ops = { .read_time = max6900_rtc_read_time, .set_time = max6900_rtc_set_time, }; static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind) { int rc = 0; struct i2c_client *client = NULL; struct rtc_device *rtc = NULL; if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) { rc = -ENODEV; goto failout; } client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL); if (client == NULL) { rc = -ENOMEM; goto failout; } client->addr = addr; client->adapter = adapter; client->driver = &max6900_driver; strlcpy(client->name, DRV_NAME, I2C_NAME_SIZE); if (kind < 0) { rc = max6900_i2c_validate_client(client); if (rc < 0) goto failout; } rc = i2c_attach_client(client); if (rc < 0) goto failout; dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n"); rtc = rtc_device_register(max6900_driver.driver.name, &client->dev, &max6900_rtc_ops, THIS_MODULE); if (IS_ERR(rtc)) { rc = PTR_ERR(rtc); goto failout_detach; } i2c_set_clientdata(client, rtc); return 0; failout_detach: i2c_detach_client(client); failout: kfree(client); return rc; } static int __init max6900_init(void) { return i2c_add_driver(&max6900_driver); } static void __exit max6900_exit(void) { i2c_del_driver(&max6900_driver); } MODULE_DESCRIPTION("Maxim MAX6900 RTC driver"); MODULE_LICENSE("GPL"); MODULE_VERSION(DRV_VERSION); module_init(max6900_init); module_exit(max6900_exit);