diff options
Diffstat (limited to 'drivers/rtc/rtc-m41t93.c')
| -rw-r--r-- | drivers/rtc/rtc-m41t93.c | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-m41t93.c b/drivers/rtc/rtc-m41t93.c new file mode 100644 index 000000000..9444cb5f5 --- /dev/null +++ b/drivers/rtc/rtc-m41t93.c @@ -0,0 +1,206 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * + * Driver for ST M41T93 SPI RTC + * + * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH + */ + +#include <linux/bcd.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/rtc.h> +#include <linux/spi/spi.h> + +#define M41T93_REG_SSEC 0 +#define M41T93_REG_ST_SEC 1 +#define M41T93_REG_MIN 2 +#define M41T93_REG_CENT_HOUR 3 +#define M41T93_REG_WDAY 4 +#define M41T93_REG_DAY 5 +#define M41T93_REG_MON 6 +#define M41T93_REG_YEAR 7 + + +#define M41T93_REG_ALM_HOUR_HT 0xc +#define M41T93_REG_FLAGS 0xf + +#define M41T93_FLAG_ST (1 << 7) +#define M41T93_FLAG_OF (1 << 2) +#define M41T93_FLAG_BL (1 << 4) +#define M41T93_FLAG_HT (1 << 6) + +static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data) +{ + u8 buf[2]; + + /* MSB must be '1' to write */ + buf[0] = addr | 0x80; + buf[1] = data; + + return spi_write(spi, buf, sizeof(buf)); +} + +static int m41t93_set_time(struct device *dev, struct rtc_time *tm) +{ + struct spi_device *spi = to_spi_device(dev); + int tmp; + u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */ + u8 * const data = &buf[1]; /* ptr to first data byte */ + + dev_dbg(dev, "%s secs=%d, mins=%d, " + "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", + "write", tm->tm_sec, tm->tm_min, + tm->tm_hour, tm->tm_mday, + tm->tm_mon, tm->tm_year, tm->tm_wday); + + if (tm->tm_year < 100) { + dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n"); + return -EINVAL; + } + + tmp = spi_w8r8(spi, M41T93_REG_FLAGS); + if (tmp < 0) + return tmp; + + if (tmp & M41T93_FLAG_OF) { + dev_warn(&spi->dev, "OF bit is set, resetting.\n"); + m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF); + + tmp = spi_w8r8(spi, M41T93_REG_FLAGS); + if (tmp < 0) { + return tmp; + } else if (tmp & M41T93_FLAG_OF) { + /* OF cannot be immediately reset: oscillator has to be + * restarted. */ + u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST; + + dev_warn(&spi->dev, + "OF bit is still set, kickstarting clock.\n"); + m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc); + reset_osc &= ~M41T93_FLAG_ST; + m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc); + } + } + + data[M41T93_REG_SSEC] = 0; + data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec); + data[M41T93_REG_MIN] = bin2bcd(tm->tm_min); + data[M41T93_REG_CENT_HOUR] = bin2bcd(tm->tm_hour) | + ((tm->tm_year/100-1) << 6); + data[M41T93_REG_DAY] = bin2bcd(tm->tm_mday); + data[M41T93_REG_WDAY] = bin2bcd(tm->tm_wday + 1); + data[M41T93_REG_MON] = bin2bcd(tm->tm_mon + 1); + data[M41T93_REG_YEAR] = bin2bcd(tm->tm_year % 100); + + return spi_write(spi, buf, sizeof(buf)); +} + + +static int m41t93_get_time(struct device *dev, struct rtc_time *tm) +{ + struct spi_device *spi = to_spi_device(dev); + const u8 start_addr = 0; + u8 buf[8]; + int century_after_1900; + int tmp; + int ret = 0; + + /* Check status of clock. Two states must be considered: + 1. halt bit (HT) is set: the clock is running but update of readout + registers has been disabled due to power failure. This is normal + case after poweron. Time is valid after resetting HT bit. + 2. oscillator fail bit (OF) is set: time is invalid. + */ + tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT); + if (tmp < 0) + return tmp; + + if (tmp & M41T93_FLAG_HT) { + dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n"); + m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT, + tmp & ~M41T93_FLAG_HT); + } + + tmp = spi_w8r8(spi, M41T93_REG_FLAGS); + if (tmp < 0) + return tmp; + + if (tmp & M41T93_FLAG_OF) { + ret = -EINVAL; + dev_warn(&spi->dev, "OF bit is set, write time to restart.\n"); + } + + if (tmp & M41T93_FLAG_BL) + dev_warn(&spi->dev, "BL bit is set, replace battery.\n"); + + /* read actual time/date */ + tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf)); + if (tmp < 0) + return tmp; + + tm->tm_sec = bcd2bin(buf[M41T93_REG_ST_SEC]); + tm->tm_min = bcd2bin(buf[M41T93_REG_MIN]); + tm->tm_hour = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f); + tm->tm_mday = bcd2bin(buf[M41T93_REG_DAY]); + tm->tm_mon = bcd2bin(buf[M41T93_REG_MON]) - 1; + tm->tm_wday = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1; + + century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1; + tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100; + + dev_dbg(dev, "%s secs=%d, mins=%d, " + "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", + "read", tm->tm_sec, tm->tm_min, + tm->tm_hour, tm->tm_mday, + tm->tm_mon, tm->tm_year, tm->tm_wday); + + return ret; +} + + +static const struct rtc_class_ops m41t93_rtc_ops = { + .read_time = m41t93_get_time, + .set_time = m41t93_set_time, +}; + +static struct spi_driver m41t93_driver; + +static int m41t93_probe(struct spi_device *spi) +{ + struct rtc_device *rtc; + int res; + + spi->bits_per_word = 8; + spi_setup(spi); + + res = spi_w8r8(spi, M41T93_REG_WDAY); + if (res < 0 || (res & 0xf8) != 0) { + dev_err(&spi->dev, "not found 0x%x.\n", res); + return -ENODEV; + } + + rtc = devm_rtc_device_register(&spi->dev, m41t93_driver.driver.name, + &m41t93_rtc_ops, THIS_MODULE); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + spi_set_drvdata(spi, rtc); + + return 0; +} + +static struct spi_driver m41t93_driver = { + .driver = { + .name = "rtc-m41t93", + }, + .probe = m41t93_probe, +}; + +module_spi_driver(m41t93_driver); + +MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>"); +MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("spi:rtc-m41t93"); |