diff options
Diffstat (limited to 'drivers/rtc/rtc-spacemit-p1.c')
| -rw-r--r-- | drivers/rtc/rtc-spacemit-p1.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-spacemit-p1.c b/drivers/rtc/rtc-spacemit-p1.c new file mode 100644 index 000000000000..43ab62494bb4 --- /dev/null +++ b/drivers/rtc/rtc-spacemit-p1.c @@ -0,0 +1,167 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Driver for the RTC found in the SpacemiT P1 PMIC + * + * Copyright (C) 2025 by RISCstar Solutions Corporation. All rights reserved. + */ + +#include <linux/bits.h> +#include <linux/device.h> +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/regmap.h> +#include <linux/rtc.h> + +#define MOD_NAME "spacemit-p1-rtc" + +/* + * Six consecutive 1-byte registers hold the seconds, minutes, hours, + * day-of-month, month, and year (respectively). + * + * The range of values in these registers is: + * seconds 0-59 + * minutes 0-59 + * hours 0-59 + * day 0-30 (struct tm is 1-31) + * month 0-11 + * year years since 2000 (struct tm is since 1900) + * + * Note that the day and month must be converted after reading and + * before writing. + */ +#define RTC_TIME 0x0d /* Offset of the seconds register */ + +#define RTC_CTRL 0x1d +#define RTC_EN BIT(2) + +/* Number of attempts to read a consistent time stamp before giving up */ +#define RTC_READ_TRIES 20 /* At least 1 */ + +struct p1_rtc { + struct regmap *regmap; + struct rtc_device *rtc; +}; + +/* + * The P1 hardware documentation states that the register values are + * latched to ensure a consistent time snapshot within the registers, + * but these are in fact unstable due to a bug in the hardware design. + * So we loop until we get two identical readings. + */ +static int p1_rtc_read_time(struct device *dev, struct rtc_time *t) +{ + struct p1_rtc *p1 = dev_get_drvdata(dev); + struct regmap *regmap = p1->regmap; + u32 count = RTC_READ_TRIES; + u8 seconds; + u8 time[6]; + int ret; + + if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN)) + return -EINVAL; /* RTC is disabled */ + + ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time)); + if (ret) + return ret; + + do { + seconds = time[0]; + ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time)); + if (ret) + return ret; + } while (time[0] != seconds && --count); + + if (!count) + return -EIO; /* Unable to get a consistent result */ + + t->tm_sec = time[0] & GENMASK(5, 0); + t->tm_min = time[1] & GENMASK(5, 0); + t->tm_hour = time[2] & GENMASK(4, 0); + t->tm_mday = (time[3] & GENMASK(4, 0)) + 1; + t->tm_mon = time[4] & GENMASK(3, 0); + t->tm_year = (time[5] & GENMASK(5, 0)) + 100; + + return 0; +} + +/* + * The P1 hardware documentation states that values in the registers are + * latched so when written they represent a consistent time snapshot. + * Nevertheless, this is not guaranteed by the implementation, so we must + * disable the RTC while updating it. + */ +static int p1_rtc_set_time(struct device *dev, struct rtc_time *t) +{ + struct p1_rtc *p1 = dev_get_drvdata(dev); + struct regmap *regmap = p1->regmap; + u8 time[6]; + int ret; + + time[0] = t->tm_sec; + time[1] = t->tm_min; + time[2] = t->tm_hour; + time[3] = t->tm_mday - 1; + time[4] = t->tm_mon; + time[5] = t->tm_year - 100; + + /* Disable the RTC to update; re-enable again when done */ + ret = regmap_clear_bits(regmap, RTC_CTRL, RTC_EN); + if (ret) + return ret; + + /* If something goes wrong, leave the RTC disabled */ + ret = regmap_bulk_write(regmap, RTC_TIME, time, sizeof(time)); + if (ret) + return ret; + + return regmap_set_bits(regmap, RTC_CTRL, RTC_EN); +} + +static const struct rtc_class_ops p1_rtc_class_ops = { + .read_time = p1_rtc_read_time, + .set_time = p1_rtc_set_time, +}; + +static int p1_rtc_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct rtc_device *rtc; + struct p1_rtc *p1; + + p1 = devm_kzalloc(dev, sizeof(*p1), GFP_KERNEL); + if (!p1) + return -ENOMEM; + dev_set_drvdata(dev, p1); + + p1->regmap = dev_get_regmap(dev->parent, NULL); + if (!p1->regmap) + return dev_err_probe(dev, -ENODEV, "failed to get regmap\n"); + + rtc = devm_rtc_allocate_device(dev); + if (IS_ERR(rtc)) + return dev_err_probe(dev, PTR_ERR(rtc), + "error allocating device\n"); + p1->rtc = rtc; + + rtc->ops = &p1_rtc_class_ops; + rtc->range_min = RTC_TIMESTAMP_BEGIN_2000; + rtc->range_max = RTC_TIMESTAMP_END_2063; + + clear_bit(RTC_FEATURE_ALARM, rtc->features); + clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features); + + return devm_rtc_register_device(rtc); +} + +static struct platform_driver p1_rtc_driver = { + .probe = p1_rtc_probe, + .driver = { + .name = MOD_NAME, + }, +}; + +module_platform_driver(p1_rtc_driver); + +MODULE_DESCRIPTION("SpacemiT P1 RTC driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:" MOD_NAME); |