--- /dev/null
+/*
+ * 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_VERSION "0.2"
+
+/*
+ * 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 */
+
+static struct i2c_driver max6900_driver;
+
+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_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 rtc_valid_tm(tm);
+}
+
+static int max6900_i2c_clear_write_protect(struct i2c_client *client)
+{
+ return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 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 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_client *client, const struct i2c_device_id *id)
+{
+ struct rtc_device *rtc;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+ return -ENODEV;
+
+ dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
+
+ rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
+ &max6900_rtc_ops, THIS_MODULE);
+ if (IS_ERR(rtc))
+ return PTR_ERR(rtc);
+
+ i2c_set_clientdata(client, rtc);
+
+ return 0;
+}
+
+static struct i2c_device_id max6900_id[] = {
+ { "max6900", 0 },
+ { }
+};
+
+static struct i2c_driver max6900_driver = {
+ .driver = {
+ .name = "rtc-max6900",
+ },
+ .probe = max6900_probe,
+ .id_table = max6900_id,
+};
+
+module_i2c_driver(max6900_driver);
+
+MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
+MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRV_VERSION);
Code Review / kvmfornfv.git / blobdiff