Commit a6de182d authored by Alex Elder's avatar Alex Elder Committed by Alexandre Belloni
Browse files

rtc: spacemit: support the SpacemiT P1 RTC 



Add support for the RTC found in the SpacemiT P1 PMIC.  Initially
only setting and reading the time are supported.

The PMIC is implemented as a multi-function device.  This RTC is
probed based on this driver being named in a MFD cell in the simple
MFD I2C driver.

Signed-off-by: default avatarAlex Elder <elder@riscstar.com>
Acked-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20250825172057.163883-5-elder@riscstar.com


Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
parent 6266aea8

drivers/rtc/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -406,6 +406,16 @@ config RTC_DRV_MAX77686 
	  This driver can also be built as a module. If so, the module

	  will be called rtc-max77686.



config RTC_DRV_SPACEMIT_P1

	tristate "SpacemiT P1 RTC"

	depends on ARCH_SPACEMIT || COMPILE_TEST

	select MFD_SPACEMIT_P1

	default ARCH_SPACEMIT

	help

	  Enable support for the RTC function in the SpacemiT P1 PMIC.

	  This driver can also be built as a module, which will be called

	  "spacemit-p1-rtc".



config RTC_DRV_NCT3018Y

	tristate "Nuvoton NCT3018Y"

	depends on OF

drivers/rtc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -171,6 +171,7 @@ obj-$(CONFIG_RTC_DRV_SD2405AL) += rtc-sd2405al.o 
obj-$(CONFIG_RTC_DRV_SD3078)	+= rtc-sd3078.o

obj-$(CONFIG_RTC_DRV_SH)	+= rtc-sh.o

obj-$(CONFIG_RTC_DRV_SNVS)	+= rtc-snvs.o

obj-$(CONFIG_RTC_DRV_SPACEMIT_P1)	+= rtc-spacemit-p1.o

obj-$(CONFIG_RTC_DRV_SPEAR)	+= rtc-spear.o

obj-$(CONFIG_RTC_DRV_STARFIRE)	+= rtc-starfire.o

obj-$(CONFIG_RTC_DRV_STK17TA8)	+= rtc-stk17ta8.o

drivers/rtc/rtc-spacemit-p1.c

0 → 100644
+167 −0
Original line number Diff line number Diff line 
// 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);