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- /*
- * SPI Driver for Microchip MCP795 RTC
- *
- * Copyright (C) Josef Gajdusek <atx@atx.name>
- *
- * based on other Linux RTC drivers
- *
- * Device datasheet:
- * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- */
- #include <linux/module.h>
- #include <linux/kernel.h>
- #include <linux/device.h>
- #include <linux/printk.h>
- #include <linux/spi/spi.h>
- #include <linux/rtc.h>
- #include <linux/of.h>
- #include <linux/bcd.h>
- #include <linux/delay.h>
- /* MCP795 Instructions, see datasheet table 3-1 */
- #define MCP795_EEREAD 0x03
- #define MCP795_EEWRITE 0x02
- #define MCP795_EEWRDI 0x04
- #define MCP795_EEWREN 0x06
- #define MCP795_SRREAD 0x05
- #define MCP795_SRWRITE 0x01
- #define MCP795_READ 0x13
- #define MCP795_WRITE 0x12
- #define MCP795_UNLOCK 0x14
- #define MCP795_IDWRITE 0x32
- #define MCP795_IDREAD 0x33
- #define MCP795_CLRWDT 0x44
- #define MCP795_CLRRAM 0x54
- /* MCP795 RTCC registers, see datasheet table 4-1 */
- #define MCP795_REG_SECONDS 0x01
- #define MCP795_REG_DAY 0x04
- #define MCP795_REG_MONTH 0x06
- #define MCP795_REG_CONTROL 0x08
- #define MCP795_REG_ALM0_SECONDS 0x0C
- #define MCP795_REG_ALM0_DAY 0x0F
- #define MCP795_ST_BIT BIT(7)
- #define MCP795_24_BIT BIT(6)
- #define MCP795_LP_BIT BIT(5)
- #define MCP795_EXTOSC_BIT BIT(3)
- #define MCP795_OSCON_BIT BIT(5)
- #define MCP795_ALM0_BIT BIT(4)
- #define MCP795_ALM1_BIT BIT(5)
- #define MCP795_ALM0IF_BIT BIT(3)
- #define MCP795_ALM0C0_BIT BIT(4)
- #define MCP795_ALM0C1_BIT BIT(5)
- #define MCP795_ALM0C2_BIT BIT(6)
- #define SEC_PER_DAY (24 * 60 * 60)
- static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
- {
- struct spi_device *spi = to_spi_device(dev);
- int ret;
- u8 tx[2];
- tx[0] = MCP795_READ;
- tx[1] = addr;
- ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);
- if (ret)
- dev_err(dev, "Failed reading %d bytes from address %x.\n",
- count, addr);
- return ret;
- }
- static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)
- {
- struct spi_device *spi = to_spi_device(dev);
- int ret;
- u8 tx[257];
- tx[0] = MCP795_WRITE;
- tx[1] = addr;
- memcpy(&tx[2], data, count);
- ret = spi_write(spi, tx, 2 + count);
- if (ret)
- dev_err(dev, "Failed to write %d bytes to address %x.\n",
- count, addr);
- return ret;
- }
- static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
- {
- int ret;
- u8 tmp;
- ret = mcp795_rtcc_read(dev, addr, &tmp, 1);
- if (ret)
- return ret;
- if ((tmp & mask) != state) {
- tmp = (tmp & ~mask) | state;
- ret = mcp795_rtcc_write(dev, addr, &tmp, 1);
- }
- return ret;
- }
- static int mcp795_stop_oscillator(struct device *dev, bool *extosc)
- {
- int retries = 5;
- int ret;
- u8 data;
- ret = mcp795_rtcc_set_bits(dev, MCP795_REG_SECONDS, MCP795_ST_BIT, 0);
- if (ret)
- return ret;
- ret = mcp795_rtcc_read(dev, MCP795_REG_CONTROL, &data, 1);
- if (ret)
- return ret;
- *extosc = !!(data & MCP795_EXTOSC_BIT);
- ret = mcp795_rtcc_set_bits(
- dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, 0);
- if (ret)
- return ret;
- /* wait for the OSCON bit to clear */
- do {
- usleep_range(700, 800);
- ret = mcp795_rtcc_read(dev, MCP795_REG_DAY, &data, 1);
- if (ret)
- break;
- if (!(data & MCP795_OSCON_BIT))
- break;
- } while (--retries);
- return !retries ? -EIO : ret;
- }
- static int mcp795_start_oscillator(struct device *dev, bool *extosc)
- {
- if (extosc) {
- u8 data = *extosc ? MCP795_EXTOSC_BIT : 0;
- int ret;
- ret = mcp795_rtcc_set_bits(
- dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, data);
- if (ret)
- return ret;
- }
- return mcp795_rtcc_set_bits(
- dev, MCP795_REG_SECONDS, MCP795_ST_BIT, MCP795_ST_BIT);
- }
- /* Enable or disable Alarm 0 in RTC */
- static int mcp795_update_alarm(struct device *dev, bool enable)
- {
- int ret;
- dev_dbg(dev, "%s alarm\n", enable ? "Enable" : "Disable");
- if (enable) {
- /* clear ALM0IF (Alarm 0 Interrupt Flag) bit */
- ret = mcp795_rtcc_set_bits(dev, MCP795_REG_ALM0_DAY,
- MCP795_ALM0IF_BIT, 0);
- if (ret)
- return ret;
- /* enable alarm 0 */
- ret = mcp795_rtcc_set_bits(dev, MCP795_REG_CONTROL,
- MCP795_ALM0_BIT, MCP795_ALM0_BIT);
- } else {
- /* disable alarm 0 and alarm 1 */
- ret = mcp795_rtcc_set_bits(dev, MCP795_REG_CONTROL,
- MCP795_ALM0_BIT | MCP795_ALM1_BIT, 0);
- }
- return ret;
- }
- static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
- {
- int ret;
- u8 data[7];
- bool extosc;
- /* Stop RTC and store current value of EXTOSC bit */
- ret = mcp795_stop_oscillator(dev, &extosc);
- if (ret)
- return ret;
- /* Read first, so we can leave config bits untouched */
- ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data));
- if (ret)
- return ret;
- data[0] = (data[0] & 0x80) | bin2bcd(tim->tm_sec);
- data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min);
- data[2] = bin2bcd(tim->tm_hour);
- data[3] = (data[3] & 0xF8) | bin2bcd(tim->tm_wday + 1);
- data[4] = bin2bcd(tim->tm_mday);
- data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon + 1);
- if (tim->tm_year > 100)
- tim->tm_year -= 100;
- data[6] = bin2bcd(tim->tm_year);
- /* Always write the date and month using a separate Write command.
- * This is a workaround for a know silicon issue that some combinations
- * of date and month values may result in the date being reset to 1.
- */
- ret = mcp795_rtcc_write(dev, MCP795_REG_SECONDS, data, 5);
- if (ret)
- return ret;
- ret = mcp795_rtcc_write(dev, MCP795_REG_MONTH, &data[5], 2);
- if (ret)
- return ret;
- /* Start back RTC and restore previous value of EXTOSC bit.
- * There is no need to clear EXTOSC bit when the previous value was 0
- * because it was already cleared when stopping the RTC oscillator.
- */
- ret = mcp795_start_oscillator(dev, extosc ? &extosc : NULL);
- if (ret)
- return ret;
- dev_dbg(dev, "Set mcp795: %04d-%02d-%02d(%d) %02d:%02d:%02d\n",
- tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
- tim->tm_wday, tim->tm_hour, tim->tm_min, tim->tm_sec);
- return 0;
- }
- static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
- {
- int ret;
- u8 data[7];
- ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data));
- if (ret)
- return ret;
- tim->tm_sec = bcd2bin(data[0] & 0x7F);
- tim->tm_min = bcd2bin(data[1] & 0x7F);
- tim->tm_hour = bcd2bin(data[2] & 0x3F);
- tim->tm_wday = bcd2bin(data[3] & 0x07) - 1;
- tim->tm_mday = bcd2bin(data[4] & 0x3F);
- tim->tm_mon = bcd2bin(data[5] & 0x1F) - 1;
- tim->tm_year = bcd2bin(data[6]) + 100; /* Assume we are in 20xx */
- dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d(%d) %02d:%02d:%02d\n",
- tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
- tim->tm_wday, tim->tm_hour, tim->tm_min, tim->tm_sec);
- return 0;
- }
- static int mcp795_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
- {
- struct rtc_time now_tm;
- time64_t now;
- time64_t later;
- u8 tmp[6];
- int ret;
- /* Read current time from RTC hardware */
- ret = mcp795_read_time(dev, &now_tm);
- if (ret)
- return ret;
- /* Get the number of seconds since 1970 */
- now = rtc_tm_to_time64(&now_tm);
- later = rtc_tm_to_time64(&alm->time);
- if (later <= now)
- return -EINVAL;
- /* make sure alarm fires within the next one year */
- if ((later - now) >=
- (SEC_PER_DAY * (365 + is_leap_year(alm->time.tm_year))))
- return -EDOM;
- /* disable alarm */
- ret = mcp795_update_alarm(dev, false);
- if (ret)
- return ret;
- /* Read registers, so we can leave configuration bits untouched */
- ret = mcp795_rtcc_read(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp));
- if (ret)
- return ret;
- alm->time.tm_year = -1;
- alm->time.tm_isdst = -1;
- alm->time.tm_yday = -1;
- tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec);
- tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min);
- tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour);
- tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1);
- /* set alarm match: seconds, minutes, hour, day, date and month */
- tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT | MCP795_ALM0C0_BIT);
- tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday);
- tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1);
- ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp, sizeof(tmp));
- if (ret)
- return ret;
- /* enable alarm if requested */
- if (alm->enabled) {
- ret = mcp795_update_alarm(dev, true);
- if (ret)
- return ret;
- dev_dbg(dev, "Alarm IRQ armed\n");
- }
- dev_dbg(dev, "Set alarm: %02d-%02d(%d) %02d:%02d:%02d\n",
- alm->time.tm_mon, alm->time.tm_mday, alm->time.tm_wday,
- alm->time.tm_hour, alm->time.tm_min, alm->time.tm_sec);
- return 0;
- }
- static int mcp795_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
- {
- u8 data[6];
- int ret;
- ret = mcp795_rtcc_read(
- dev, MCP795_REG_ALM0_SECONDS, data, sizeof(data));
- if (ret)
- return ret;
- alm->time.tm_sec = bcd2bin(data[0] & 0x7F);
- alm->time.tm_min = bcd2bin(data[1] & 0x7F);
- alm->time.tm_hour = bcd2bin(data[2] & 0x1F);
- alm->time.tm_wday = bcd2bin(data[3] & 0x07) - 1;
- alm->time.tm_mday = bcd2bin(data[4] & 0x3F);
- alm->time.tm_mon = bcd2bin(data[5] & 0x1F) - 1;
- alm->time.tm_year = -1;
- alm->time.tm_isdst = -1;
- alm->time.tm_yday = -1;
- dev_dbg(dev, "Read alarm: %02d-%02d(%d) %02d:%02d:%02d\n",
- alm->time.tm_mon, alm->time.tm_mday, alm->time.tm_wday,
- alm->time.tm_hour, alm->time.tm_min, alm->time.tm_sec);
- return 0;
- }
- static int mcp795_alarm_irq_enable(struct device *dev, unsigned int enabled)
- {
- return mcp795_update_alarm(dev, !!enabled);
- }
- static irqreturn_t mcp795_irq(int irq, void *data)
- {
- struct spi_device *spi = data;
- struct rtc_device *rtc = spi_get_drvdata(spi);
- struct mutex *lock = &rtc->ops_lock;
- int ret;
- mutex_lock(lock);
- /* Disable alarm.
- * There is no need to clear ALM0IF (Alarm 0 Interrupt Flag) bit,
- * because it is done every time when alarm is enabled.
- */
- ret = mcp795_update_alarm(&spi->dev, false);
- if (ret)
- dev_err(&spi->dev,
- "Failed to disable alarm in IRQ (ret=%d)\n", ret);
- rtc_update_irq(rtc, 1, RTC_AF | RTC_IRQF);
- mutex_unlock(lock);
- return IRQ_HANDLED;
- }
- static const struct rtc_class_ops mcp795_rtc_ops = {
- .read_time = mcp795_read_time,
- .set_time = mcp795_set_time,
- .read_alarm = mcp795_read_alarm,
- .set_alarm = mcp795_set_alarm,
- .alarm_irq_enable = mcp795_alarm_irq_enable
- };
- static int mcp795_probe(struct spi_device *spi)
- {
- struct rtc_device *rtc;
- int ret;
- spi->mode = SPI_MODE_0;
- spi->bits_per_word = 8;
- ret = spi_setup(spi);
- if (ret) {
- dev_err(&spi->dev, "Unable to setup SPI\n");
- return ret;
- }
- /* Start the oscillator but don't set the value of EXTOSC bit */
- mcp795_start_oscillator(&spi->dev, NULL);
- /* Clear the 12 hour mode flag*/
- mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
- rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795",
- &mcp795_rtc_ops, THIS_MODULE);
- if (IS_ERR(rtc))
- return PTR_ERR(rtc);
- spi_set_drvdata(spi, rtc);
- if (spi->irq > 0) {
- dev_dbg(&spi->dev, "Alarm support enabled\n");
- /* Clear any pending alarm (ALM0IF bit) before requesting
- * the interrupt.
- */
- mcp795_rtcc_set_bits(&spi->dev, MCP795_REG_ALM0_DAY,
- MCP795_ALM0IF_BIT, 0);
- ret = devm_request_threaded_irq(&spi->dev, spi->irq, NULL,
- mcp795_irq, IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
- dev_name(&rtc->dev), spi);
- if (ret)
- dev_err(&spi->dev, "Failed to request IRQ: %d: %d\n",
- spi->irq, ret);
- else
- device_init_wakeup(&spi->dev, true);
- }
- return 0;
- }
- #ifdef CONFIG_OF
- static const struct of_device_id mcp795_of_match[] = {
- { .compatible = "maxim,mcp795" },
- { }
- };
- MODULE_DEVICE_TABLE(of, mcp795_of_match);
- #endif
- static struct spi_driver mcp795_driver = {
- .driver = {
- .name = "rtc-mcp795",
- .of_match_table = of_match_ptr(mcp795_of_match),
- },
- .probe = mcp795_probe,
- };
- module_spi_driver(mcp795_driver);
- MODULE_DESCRIPTION("MCP795 RTC SPI Driver");
- MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>");
- MODULE_LICENSE("GPL");
- MODULE_ALIAS("spi:mcp795");
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