// SPDX-License-Identifier: GPL-2.0-only
/*
* Dallas DS1302 RTC Support
*
* Copyright (C) 2002 David McCullough
* Copyright (C) 2003 - 2007 Paul Mundt
*/
#include <linux/bcd.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#define RTC_CMD_READ 0x81 /* Read command */
#define RTC_CMD_WRITE 0x80 /* Write command */
#define RTC_CMD_WRITE_ENABLE 0x00 /* Write enable */
#define RTC_CMD_WRITE_DISABLE 0x80 /* Write disable */
#define RTC_ADDR_RAM0 0x20 /* Address of RAM0 */
#define RTC_ADDR_TCR 0x08 /* Address of trickle charge register */
#define RTC_CLCK_BURST 0x1F /* Address of clock burst */
#define RTC_CLCK_LEN 0x08 /* Size of clock burst */
#define RTC_ADDR_CTRL 0x07 /* Address of control register */
#define RTC_ADDR_YEAR 0x06 /* Address of year register */
#define RTC_ADDR_DAY 0x05 /* Address of day of week register */
#define RTC_ADDR_MON 0x04 /* Address of month register */
#define RTC_ADDR_DATE 0x03 /* Address of day of month register */
#define RTC_ADDR_HOUR 0x02 /* Address of hour register */
#define RTC_ADDR_MIN 0x01 /* Address of minute register */
#define RTC_ADDR_SEC 0x00 /* Address of second register */
static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
{
struct spi_device *spi = dev_get_drvdata(dev);
u8 buf[1 + RTC_CLCK_LEN];
u8 *bp;
int status;
/* Enable writing */
bp = buf;
*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
*bp++ = RTC_CMD_WRITE_ENABLE;
status = spi_write_then_read(spi, buf, 2,
NULL, 0);
if (status)
return status;
/* Write registers starting at the first time/date address. */
bp = buf;
*bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
*bp++ = bin2bcd(time->tm_sec);
*bp++ = bin2bcd(time->tm_min);
*bp++ = bin2bcd(time->tm_hour);
*bp++ = bin2bcd(time->tm_mday);
*bp++ = bin2bcd(time->tm_mon + 1);
*bp++ = time->tm_wday + 1;
*bp++ = bin2bcd(time->tm_year % 100);
*bp++ = RTC_CMD_WRITE_DISABLE;
/* use write-then-read since dma from stack is nonportable */
return spi_write_then_read(spi, buf, sizeof(buf),
NULL, 0);
}
static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
{
struct spi_device *spi = dev_get_drvdata(dev);
u8 addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
u8 buf[RTC_CLCK_LEN - 1];
int status;
/* Use write-then-read to get all the date/time registers
* since dma from stack is nonportable
*/
status = spi_write_then_read(spi, &addr, sizeof(addr),
buf, sizeof(buf));
if (status < 0)
return status;
/* Decode the registers */
time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
time->tm_wday = buf[RTC_ADDR_DAY] - 1;
time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
return 0;
}
static const struct rtc_class_ops ds1302_rtc_ops = {
.read_time = ds1302_rtc_get_time,
.set_time = ds1302_rtc_set_time,
};
static int ds1302_probe(struct spi_device *spi)
{
struct rtc_device *rtc;
u8 addr;
u8 buf[4];
u8 *bp;
int status;
/* Sanity check board setup data. This may be hooked up
* in 3wire mode, but we don't care. Note that unless
* there's an inverter in place, this needs SPI_CS_HIGH!
*/
if (spi->bits_per_word && (spi->bits_per_word != 8)) {
dev_err(&spi->dev, "bad word length\n");
return -EINVAL;
} else if (spi->max_speed_hz > 2000000) {
dev_err(&spi->dev, "speed is too high\n");
return -EINVAL;
} else if (spi->mode & SPI_CPHA) {
dev_err(&spi->dev, "bad mode\n");
return -EINVAL;
}
addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
if (status < 0) {
dev_err(&spi->dev, "control register read error %d\n",
status);
return status;
}
if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
if (status < 0) {
dev_err(&spi->dev, "control register read error %d\n",
status);
return status;
}
if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
dev_err(&spi->dev, "junk in control register\n");
return -ENODEV;
}
}
if (buf[0] == 0) {
bp = buf;
*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
*bp++ = RTC_CMD_WRITE_DISABLE;
status = spi_write_then_read(spi, buf, 2, NULL, 0);
if (status < 0) {
dev_err(&spi->dev, "control register write error %d\n",
status);
return status;
}
addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
if (status < 0) {
dev_err(&spi->dev,
"error %d reading control register\n",
status);
return status;
}
if (buf[0] != RTC_CMD_WRITE_DISABLE) {
dev_err(&spi->dev, "failed to detect chip\n");
return -ENODEV;
}
}
spi_set_drvdata(spi, spi);
rtc = devm_rtc_device_register(&spi->dev, "ds1302",
&ds1302_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc)) {
status = PTR_ERR(rtc);
dev_err(&spi->dev, "error %d registering rtc\n", status);
return status;
}
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id ds1302_dt_ids[] = {
{ .compatible = "maxim,ds1302", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
#endif
static const struct spi_device_id ds1302_spi_ids[] = {
{ .name = "ds1302", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(spi, ds1302_spi_ids);
static struct spi_driver ds1302_driver = {
.driver.name = "rtc-ds1302",
.driver.of_match_table = of_match_ptr(ds1302_dt_ids),
.probe = ds1302_probe,
.id_table = ds1302_spi_ids,
};
module_spi_driver(ds1302_driver);
MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
MODULE_AUTHOR("Paul Mundt, David McCullough");
MODULE_LICENSE("GPL v2");
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