diff options
Diffstat (limited to 'drivers/rtc/rtc-mcp795.c')
| -rw-r--r-- | drivers/rtc/rtc-mcp795.c | 453 |
1 files changed, 453 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c new file mode 100644 index 000000000..0d515b3df --- /dev/null +++ b/drivers/rtc/rtc-mcp795.c @@ -0,0 +1,453 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * SPI Driver for Microchip MCP795 RTC + * + * Copyright (C) Josef Gajdusek <atx@atx.name> + * + * based on other Linux RTC drivers + * + * Device datasheet: + * https://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf + */ + +#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: %ptR\n", tim); + + 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: %ptR\n", tim); + + 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: %ptRdr(%d) %ptRt\n", + &alm->time, alm->time.tm_wday, &alm->time); + 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: %ptRdr(%d) %ptRt\n", + &alm->time, alm->time.tm_wday, &alm->time); + 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); + int ret; + + rtc_lock(rtc); + + /* 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); + + rtc_unlock(rtc); + + 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 const struct spi_device_id mcp795_spi_ids[] = { + { .name = "mcp795" }, + { } +}; +MODULE_DEVICE_TABLE(spi, mcp795_spi_ids); + +static struct spi_driver mcp795_driver = { + .driver = { + .name = "rtc-mcp795", + .of_match_table = of_match_ptr(mcp795_of_match), + }, + .probe = mcp795_probe, + .id_table = mcp795_spi_ids, +}; + +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"); |