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1// SPDX-License-Identifier: GPL-2.0-only2/*3 *4 * Driver for ST M41T93 SPI RTC5 *6 * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH7 */8 9#include <linux/bcd.h>10#include <linux/kernel.h>11#include <linux/module.h>12#include <linux/platform_device.h>13#include <linux/rtc.h>14#include <linux/spi/spi.h>15 16#define M41T93_REG_SSEC 017#define M41T93_REG_ST_SEC 118#define M41T93_REG_MIN 219#define M41T93_REG_CENT_HOUR 320#define M41T93_REG_WDAY 421#define M41T93_REG_DAY 522#define M41T93_REG_MON 623#define M41T93_REG_YEAR 724 25 26#define M41T93_REG_ALM_HOUR_HT 0xc27#define M41T93_REG_FLAGS 0xf28 29#define M41T93_FLAG_ST (1 << 7)30#define M41T93_FLAG_OF (1 << 2)31#define M41T93_FLAG_BL (1 << 4)32#define M41T93_FLAG_HT (1 << 6)33 34static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)35{36 u8 buf[2];37 38 /* MSB must be '1' to write */39 buf[0] = addr | 0x80;40 buf[1] = data;41 42 return spi_write(spi, buf, sizeof(buf));43}44 45static int m41t93_set_time(struct device *dev, struct rtc_time *tm)46{47 struct spi_device *spi = to_spi_device(dev);48 int tmp;49 u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */50 u8 * const data = &buf[1]; /* ptr to first data byte */51 52 dev_dbg(dev, "%s secs=%d, mins=%d, "53 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",54 "write", tm->tm_sec, tm->tm_min,55 tm->tm_hour, tm->tm_mday,56 tm->tm_mon, tm->tm_year, tm->tm_wday);57 58 if (tm->tm_year < 100) {59 dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");60 return -EINVAL;61 }62 63 tmp = spi_w8r8(spi, M41T93_REG_FLAGS);64 if (tmp < 0)65 return tmp;66 67 if (tmp & M41T93_FLAG_OF) {68 dev_warn(&spi->dev, "OF bit is set, resetting.\n");69 m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);70 71 tmp = spi_w8r8(spi, M41T93_REG_FLAGS);72 if (tmp < 0) {73 return tmp;74 } else if (tmp & M41T93_FLAG_OF) {75 /* OF cannot be immediately reset: oscillator has to be76 * restarted. */77 u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;78 79 dev_warn(&spi->dev,80 "OF bit is still set, kickstarting clock.\n");81 m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);82 reset_osc &= ~M41T93_FLAG_ST;83 m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);84 }85 }86 87 data[M41T93_REG_SSEC] = 0;88 data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec);89 data[M41T93_REG_MIN] = bin2bcd(tm->tm_min);90 data[M41T93_REG_CENT_HOUR] = bin2bcd(tm->tm_hour) |91 ((tm->tm_year/100-1) << 6);92 data[M41T93_REG_DAY] = bin2bcd(tm->tm_mday);93 data[M41T93_REG_WDAY] = bin2bcd(tm->tm_wday + 1);94 data[M41T93_REG_MON] = bin2bcd(tm->tm_mon + 1);95 data[M41T93_REG_YEAR] = bin2bcd(tm->tm_year % 100);96 97 return spi_write(spi, buf, sizeof(buf));98}99 100 101static int m41t93_get_time(struct device *dev, struct rtc_time *tm)102{103 struct spi_device *spi = to_spi_device(dev);104 const u8 start_addr = 0;105 u8 buf[8];106 int century_after_1900;107 int tmp;108 int ret = 0;109 110 /* Check status of clock. Two states must be considered:111 1. halt bit (HT) is set: the clock is running but update of readout112 registers has been disabled due to power failure. This is normal113 case after poweron. Time is valid after resetting HT bit.114 2. oscillator fail bit (OF) is set: time is invalid.115 */116 tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);117 if (tmp < 0)118 return tmp;119 120 if (tmp & M41T93_FLAG_HT) {121 dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n");122 m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT,123 tmp & ~M41T93_FLAG_HT);124 }125 126 tmp = spi_w8r8(spi, M41T93_REG_FLAGS);127 if (tmp < 0)128 return tmp;129 130 if (tmp & M41T93_FLAG_OF) {131 ret = -EINVAL;132 dev_warn(&spi->dev, "OF bit is set, write time to restart.\n");133 }134 135 if (tmp & M41T93_FLAG_BL)136 dev_warn(&spi->dev, "BL bit is set, replace battery.\n");137 138 /* read actual time/date */139 tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf));140 if (tmp < 0)141 return tmp;142 143 tm->tm_sec = bcd2bin(buf[M41T93_REG_ST_SEC]);144 tm->tm_min = bcd2bin(buf[M41T93_REG_MIN]);145 tm->tm_hour = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f);146 tm->tm_mday = bcd2bin(buf[M41T93_REG_DAY]);147 tm->tm_mon = bcd2bin(buf[M41T93_REG_MON]) - 1;148 tm->tm_wday = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1;149 150 century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1;151 tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100;152 153 dev_dbg(dev, "%s secs=%d, mins=%d, "154 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",155 "read", tm->tm_sec, tm->tm_min,156 tm->tm_hour, tm->tm_mday,157 tm->tm_mon, tm->tm_year, tm->tm_wday);158 159 return ret;160}161 162 163static const struct rtc_class_ops m41t93_rtc_ops = {164 .read_time = m41t93_get_time,165 .set_time = m41t93_set_time,166};167 168static struct spi_driver m41t93_driver;169 170static int m41t93_probe(struct spi_device *spi)171{172 struct rtc_device *rtc;173 int res;174 175 spi->bits_per_word = 8;176 spi_setup(spi);177 178 res = spi_w8r8(spi, M41T93_REG_WDAY);179 if (res < 0 || (res & 0xf8) != 0) {180 dev_err(&spi->dev, "not found 0x%x.\n", res);181 return -ENODEV;182 }183 184 rtc = devm_rtc_device_register(&spi->dev, m41t93_driver.driver.name,185 &m41t93_rtc_ops, THIS_MODULE);186 if (IS_ERR(rtc))187 return PTR_ERR(rtc);188 189 spi_set_drvdata(spi, rtc);190 191 return 0;192}193 194static struct spi_driver m41t93_driver = {195 .driver = {196 .name = "rtc-m41t93",197 },198 .probe = m41t93_probe,199};200 201module_spi_driver(m41t93_driver);202 203MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");204MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");205MODULE_LICENSE("GPL");206MODULE_ALIAS("spi:rtc-m41t93");207