rtc: add rtc-abx80x, a driver for the Abracon AB x80x i2c rtc

This is a basic driver for the ultra-low-power Abracon AB x80x series
of RTC chips. It supports in particular, the supersets AB0805 and AB1805.
It allows reading and writing the time, and enables the supercapacitor or
battery charger.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>

3 files changed, 563 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index cad667a4049..aa6d90158cd 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -166,4 +166,13 @@ config RTC_STM32
 	help
 	  Enable STM32 RTC driver. This driver supports the rtc that is present
 	  on some STM32 SoCs.
+
+config RTC_ABX80X
+	bool "Enable Abracon ABx80x RTC driver"
+	depends on DM_RTC
+	help
+	  If you say yes here you get support for Abracon AB080X and AB180X
+	  families of ultra-low-power  battery- and capacitor-backed real-time
+	  clock chips.
+
 endmenu
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index ef66dc4bf02..6a45a9c8749 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -55,3 +55,4 @@ obj-$(CONFIG_RTC_S35392A) += s35392a.o
 obj-$(CONFIG_RTC_STM32) += stm32_rtc.o
 obj-$(CONFIG_SANDBOX) += sandbox_rtc.o
 obj-$(CONFIG_RTC_X1205) += x1205.o
+obj-$(CONFIG_RTC_ABX80X) += abx80x.o
diff --git a/drivers/rtc/abx80x.c b/drivers/rtc/abx80x.c
new file mode 100644
index 00000000000..528b06cbd69
--- /dev/null
+++ b/drivers/rtc/abx80x.c
@@ -0,0 +1,553 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A driver for the I2C members of the Abracon AB x8xx RTC family,
+ * and compatible: AB 1805 and AB 0805
+ *
+ * Copyright 2014-2015 Macq S.A.
+ * Copyright 2020 Linaro
+ *
+ * Author: Philippe De Muyter <phdm@macqel.be>
+ * Author: Alexandre Belloni <alexandre.belloni@bootlin.com>
+ * Author: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
+ *
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <i2c.h>
+#include <rtc.h>
+#include <log.h>
+
+#define ABX8XX_REG_HTH		0x00
+#define ABX8XX_REG_SC		0x01
+#define ABX8XX_REG_MN		0x02
+#define ABX8XX_REG_HR		0x03
+#define ABX8XX_REG_DA		0x04
+#define ABX8XX_REG_MO		0x05
+#define ABX8XX_REG_YR		0x06
+#define ABX8XX_REG_WD		0x07
+
+#define ABX8XX_REG_AHTH		0x08
+#define ABX8XX_REG_ASC		0x09
+#define ABX8XX_REG_AMN		0x0a
+#define ABX8XX_REG_AHR		0x0b
+#define ABX8XX_REG_ADA		0x0c
+#define ABX8XX_REG_AMO		0x0d
+#define ABX8XX_REG_AWD		0x0e
+
+#define ABX8XX_REG_STATUS	0x0f
+#define ABX8XX_STATUS_AF	BIT(2)
+#define ABX8XX_STATUS_BLF	BIT(4)
+#define ABX8XX_STATUS_WDT	BIT(6)
+
+#define ABX8XX_REG_CTRL1	0x10
+#define ABX8XX_CTRL_WRITE	BIT(0)
+#define ABX8XX_CTRL_ARST	BIT(2)
+#define ABX8XX_CTRL_12_24	BIT(6)
+
+#define ABX8XX_REG_CTRL2	0x11
+#define ABX8XX_CTRL2_RSVD	BIT(5)
+
+#define ABX8XX_REG_IRQ		0x12
+#define ABX8XX_IRQ_AIE		BIT(2)
+#define ABX8XX_IRQ_IM_1_4	(0x3 << 5)
+
+#define ABX8XX_REG_CD_TIMER_CTL	0x18
+
+#define ABX8XX_REG_OSC		0x1c
+#define ABX8XX_OSC_FOS		BIT(3)
+#define ABX8XX_OSC_BOS		BIT(4)
+#define ABX8XX_OSC_ACAL_512	BIT(5)
+#define ABX8XX_OSC_ACAL_1024	BIT(6)
+
+#define ABX8XX_OSC_OSEL		BIT(7)
+
+#define ABX8XX_REG_OSS		0x1d
+#define ABX8XX_OSS_OF		BIT(1)
+#define ABX8XX_OSS_OMODE	BIT(4)
+
+#define ABX8XX_REG_WDT		0x1b
+#define ABX8XX_WDT_WDS		BIT(7)
+#define ABX8XX_WDT_BMB_MASK	0x7c
+#define ABX8XX_WDT_BMB_SHIFT	2
+#define ABX8XX_WDT_MAX_TIME	(ABX8XX_WDT_BMB_MASK >> ABX8XX_WDT_BMB_SHIFT)
+#define ABX8XX_WDT_WRB_MASK	0x03
+#define ABX8XX_WDT_WRB_1HZ	0x02
+
+#define ABX8XX_REG_CFG_KEY	0x1f
+#define ABX8XX_CFG_KEY_OSC	0xa1
+#define ABX8XX_CFG_KEY_MISC	0x9d
+
+#define ABX8XX_REG_ID0		0x28
+
+#define ABX8XX_REG_OUT_CTRL	0x30
+#define ABX8XX_OUT_CTRL_EXDS	BIT(4)
+
+#define ABX8XX_REG_TRICKLE	0x20
+#define ABX8XX_TRICKLE_CHARGE_ENABLE	0xa0
+#define ABX8XX_TRICKLE_STANDARD_DIODE	0x8
+#define ABX8XX_TRICKLE_SCHOTTKY_DIODE	0x4
+
+static u8 trickle_resistors[] = {0, 3, 6, 11};
+
+enum abx80x_chip {AB0801, AB0803, AB0804, AB0805,
+	AB1801, AB1803, AB1804, AB1805, RV1805, ABX80X};
+
+struct abx80x_cap {
+	u16 pn;
+	bool has_tc;
+	bool has_wdog;
+};
+
+static struct abx80x_cap abx80x_caps[] = {
+	[AB0801] = {.pn = 0x0801},
+	[AB0803] = {.pn = 0x0803},
+	[AB0804] = {.pn = 0x0804, .has_tc = true, .has_wdog = true},
+	[AB0805] = {.pn = 0x0805, .has_tc = true, .has_wdog = true},
+	[AB1801] = {.pn = 0x1801},
+	[AB1803] = {.pn = 0x1803},
+	[AB1804] = {.pn = 0x1804, .has_tc = true, .has_wdog = true},
+	[AB1805] = {.pn = 0x1805, .has_tc = true, .has_wdog = true},
+	[RV1805] = {.pn = 0x1805, .has_tc = true, .has_wdog = true},
+	[ABX80X] = {.pn = 0}
+};
+
+static int abx80x_rtc_read8(struct udevice *dev, unsigned int reg)
+{
+	int ret = 0;
+	u8 buf;
+
+	if (reg > 0xff)
+		return -EINVAL;
+
+	ret = dm_i2c_read(dev, reg, &buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+
+	return buf;
+}
+
+static int abx80x_rtc_write8(struct udevice *dev, unsigned int reg, int val)
+{
+	u8 buf = (u8)val;
+
+	if (reg > 0xff)
+		return -EINVAL;
+
+	return dm_i2c_write(dev, reg, &buf, sizeof(buf));
+}
+
+static int abx80x_is_rc_mode(struct udevice *dev)
+{
+	int flags = 0;
+
+	flags =  dm_i2c_reg_read(dev, ABX8XX_REG_OSS);
+	if (flags < 0) {
+		log_err("Failed to read autocalibration attribute\n");
+		return flags;
+	}
+
+	return (flags & ABX8XX_OSS_OMODE) ? 1 : 0;
+}
+
+static int abx80x_enable_trickle_charger(struct udevice *dev, u8 trickle_cfg)
+{
+	int err;
+
+	/*
+	 * Write the configuration key register to enable access to the Trickle
+	 * register
+	 */
+	err = dm_i2c_reg_write(dev, ABX8XX_REG_CFG_KEY, ABX8XX_CFG_KEY_MISC);
+	if (err < 0) {
+		log_err("Unable to write configuration key\n");
+		return -EIO;
+	}
+
+	err = dm_i2c_reg_write(dev, ABX8XX_REG_TRICKLE,
+			       ABX8XX_TRICKLE_CHARGE_ENABLE | trickle_cfg);
+	if (err < 0) {
+		log_err("Unable to write trickle register\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int abx80x_rtc_read_time(struct udevice *dev, struct rtc_time *tm)
+{
+	unsigned char buf[8];
+	int err, flags, rc_mode = 0;
+
+	/* Read the Oscillator Failure only in XT mode */
+	rc_mode = abx80x_is_rc_mode(dev);
+	if (rc_mode < 0)
+		return rc_mode;
+
+	if (!rc_mode) {
+		flags = dm_i2c_reg_read(dev, ABX8XX_REG_OSS);
+		if (flags < 0) {
+			log_err("Unable to read oscillator status.\n");
+			return flags;
+		}
+
+		if (flags & ABX8XX_OSS_OF)
+			log_debug("Oscillator fail, data is not accurate.\n");
+	}
+
+	err = dm_i2c_read(dev, ABX8XX_REG_HTH,
+			  buf, sizeof(buf));
+	if (err < 0) {
+		log_err("Unable to read date\n");
+		return -EIO;
+	}
+
+	tm->tm_sec = bcd2bin(buf[ABX8XX_REG_SC] & 0x7F);
+	tm->tm_min = bcd2bin(buf[ABX8XX_REG_MN] & 0x7F);
+	tm->tm_hour = bcd2bin(buf[ABX8XX_REG_HR] & 0x3F);
+	tm->tm_wday = buf[ABX8XX_REG_WD] & 0x7;
+	tm->tm_mday = bcd2bin(buf[ABX8XX_REG_DA] & 0x3F);
+	tm->tm_mon = bcd2bin(buf[ABX8XX_REG_MO] & 0x1F);
+	tm->tm_year = bcd2bin(buf[ABX8XX_REG_YR]) + 2000;
+
+	return 0;
+}
+
+static int abx80x_rtc_set_time(struct udevice *dev, const struct rtc_time *tm)
+{
+	unsigned char buf[8];
+	int err, flags;
+
+	if (tm->tm_year < 2000)
+		return -EINVAL;
+
+	buf[ABX8XX_REG_HTH] = 0;
+	buf[ABX8XX_REG_SC] = bin2bcd(tm->tm_sec);
+	buf[ABX8XX_REG_MN] = bin2bcd(tm->tm_min);
+	buf[ABX8XX_REG_HR] = bin2bcd(tm->tm_hour);
+	buf[ABX8XX_REG_DA] = bin2bcd(tm->tm_mday);
+	buf[ABX8XX_REG_MO] = bin2bcd(tm->tm_mon);
+	buf[ABX8XX_REG_YR] = bin2bcd(tm->tm_year - 2000);
+	buf[ABX8XX_REG_WD] = tm->tm_wday;
+
+	err = dm_i2c_write(dev, ABX8XX_REG_HTH,
+			   buf, sizeof(buf));
+	if (err < 0) {
+		log_err("Unable to write to date registers\n");
+		return -EIO;
+	}
+
+	/* Clear the OF bit of Oscillator Status Register */
+	flags = dm_i2c_reg_read(dev, ABX8XX_REG_OSS);
+	if (flags < 0) {
+		log_err("Unable to read oscillator status.\n");
+		return flags;
+	}
+
+	err = dm_i2c_reg_write(dev, ABX8XX_REG_OSS,
+			       flags & ~ABX8XX_OSS_OF);
+	if (err < 0) {
+		log_err("Unable to write oscillator status register\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int abx80x_rtc_set_autocalibration(struct udevice *dev,
+					  int autocalibration)
+{
+	int retval, flags = 0;
+
+	if (autocalibration != 0 && autocalibration != 1024 &&
+	    autocalibration != 512) {
+		log_err("autocalibration value outside permitted range\n");
+		return -EINVAL;
+	}
+
+	flags = dm_i2c_reg_read(dev, ABX8XX_REG_OSC);
+	if (flags < 0)
+		return flags;
+
+	if (autocalibration == 0) {
+		flags &= ~(ABX8XX_OSC_ACAL_512 | ABX8XX_OSC_ACAL_1024);
+	} else if (autocalibration == 1024) {
+		/* 1024 autocalibration is 0x10 */
+		flags |= ABX8XX_OSC_ACAL_1024;
+		flags &= ~(ABX8XX_OSC_ACAL_512);
+	} else {
+		/* 512 autocalibration is 0x11 */
+		flags |= (ABX8XX_OSC_ACAL_1024 | ABX8XX_OSC_ACAL_512);
+	}
+
+	/* Unlock write access to Oscillator Control Register */
+	retval = dm_i2c_reg_write(dev, ABX8XX_REG_CFG_KEY,
+				  ABX8XX_CFG_KEY_OSC);
+	if (retval < 0) {
+		log_err("Failed to write CONFIG_KEY register\n");
+		return retval;
+	}
+
+	retval = dm_i2c_reg_write(dev, ABX8XX_REG_OSC, flags);
+
+	return retval;
+}
+
+static int abx80x_rtc_get_autocalibration(struct udevice *dev)
+{
+	int flags = 0, autocalibration;
+
+	flags =  dm_i2c_reg_read(dev, ABX8XX_REG_OSC);
+	if (flags < 0)
+		return flags;
+
+	if (flags & ABX8XX_OSC_ACAL_512)
+		autocalibration = 512;
+	else if (flags & ABX8XX_OSC_ACAL_1024)
+		autocalibration = 1024;
+	else
+		autocalibration = 0;
+
+	return autocalibration;
+}
+
+static struct rtc_time default_tm = { 0, 0, 0, 1, 1, 2000, 6, 0, 0 };
+
+static int abx80x_rtc_reset(struct udevice *dev)
+{
+	int ret = 0;
+
+	int autocalib = abx80x_rtc_get_autocalibration(dev);
+
+	if (autocalib != 0)
+		abx80x_rtc_set_autocalibration(dev, 0);
+
+	ret = abx80x_rtc_set_time(dev, &default_tm);
+	if (ret != 0) {
+		log_err("cannot set time to default_tm. error %d\n", ret);
+		return ret;
+	}
+
+	return ret;
+}
+
+static const struct rtc_ops abx80x_rtc_ops = {
+	.get	= abx80x_rtc_read_time,
+	.set	= abx80x_rtc_set_time,
+	.reset  = abx80x_rtc_reset,
+	.read8  = abx80x_rtc_read8,
+	.write8 = abx80x_rtc_write8
+};
+
+static int abx80x_dt_trickle_cfg(struct udevice *dev)
+{
+	const char *diode;
+	int trickle_cfg = 0;
+	int i, ret = 0;
+	u32 tmp;
+
+	diode = ofnode_read_string(dev_ofnode(dev), "abracon,tc-diode");
+	if (!diode)
+		return ret;
+
+	if (!strcmp(diode, "standard")) {
+		trickle_cfg |= ABX8XX_TRICKLE_STANDARD_DIODE;
+	} else if (!strcmp(diode, "schottky")) {
+		trickle_cfg |= ABX8XX_TRICKLE_SCHOTTKY_DIODE;
+	} else {
+		log_err("Invalid tc-diode value: %s\n", diode);
+		return -EINVAL;
+	}
+
+	ret = ofnode_read_u32(dev_ofnode(dev), "abracon,tc-resistor", &tmp);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < sizeof(trickle_resistors); i++)
+		if (trickle_resistors[i] == tmp)
+			break;
+
+	if (i == sizeof(trickle_resistors)) {
+		log_err("Invalid tc-resistor value: %u\n", tmp);
+		return -EINVAL;
+	}
+
+	return (trickle_cfg | i);
+}
+
+static int abx80x_probe(struct udevice *dev)
+{
+	int i, data, err, trickle_cfg = -EINVAL;
+	unsigned char buf[7];
+	unsigned int part = dev->driver_data;
+	unsigned int partnumber;
+	unsigned int majrev, minrev;
+	unsigned int lot;
+	unsigned int wafer;
+	unsigned int uid;
+
+	err = dm_i2c_read(dev, ABX8XX_REG_ID0, buf, sizeof(buf));
+	if (err < 0) {
+		log_err("Unable to read partnumber\n");
+		return -EIO;
+	}
+
+	partnumber = (buf[0] << 8) | buf[1];
+	majrev = buf[2] >> 3;
+	minrev = buf[2] & 0x7;
+	lot = ((buf[4] & 0x80) << 2) | ((buf[6] & 0x80) << 1) | buf[3];
+	uid = ((buf[4] & 0x7f) << 8) | buf[5];
+	wafer = (buf[6] & 0x7c) >> 2;
+	log_debug("model %04x, revision %u.%u, lot %x, wafer %x, uid %x\n",
+		  partnumber, majrev, minrev, lot, wafer, uid);
+
+	data = dm_i2c_reg_read(dev, ABX8XX_REG_CTRL1);
+	if (data < 0) {
+		log_err("Unable to read control register\n");
+		return -EIO;
+	}
+
+	err = dm_i2c_reg_write(dev, ABX8XX_REG_CTRL1,
+			       ((data & ~(ABX8XX_CTRL_12_24 |
+					  ABX8XX_CTRL_ARST)) |
+				ABX8XX_CTRL_WRITE));
+	if (err < 0) {
+		log_err("Unable to write control register\n");
+		return -EIO;
+	}
+
+	/* Configure RV1805 specifics */
+	if (part == RV1805) {
+		/*
+		 * Avoid accidentally entering test mode. This can happen
+		 * on the RV1805 in case the reserved bit 5 in control2
+		 * register is set. RV-1805-C3 datasheet indicates that
+		 * the bit should be cleared in section 11h - Control2.
+		 */
+		data = dm_i2c_reg_read(dev, ABX8XX_REG_CTRL2);
+		if (data < 0) {
+			log_err("Unable to read control2 register\n");
+			return -EIO;
+		}
+
+		err = dm_i2c_reg_write(dev, ABX8XX_REG_CTRL2,
+				       data & ~ABX8XX_CTRL2_RSVD);
+		if (err < 0) {
+			log_err("Unable to write control2 register\n");
+			return -EIO;
+		}
+
+		/*
+		 * Avoid extra power leakage. The RV1805 uses smaller
+		 * 10pin package and the EXTI input is not present.
+		 * Disable it to avoid leakage.
+		 */
+		data = dm_i2c_reg_read(dev, ABX8XX_REG_OUT_CTRL);
+		if (data < 0) {
+			log_err("Unable to read output control register\n");
+			return -EIO;
+		}
+
+		/*
+		 * Write the configuration key register to enable access to
+		 * the config2 register
+		 */
+		err = dm_i2c_reg_write(dev, ABX8XX_REG_CFG_KEY,
+				       ABX8XX_CFG_KEY_MISC);
+		if (err < 0) {
+			log_err("Unable to write configuration key\n");
+			return -EIO;
+		}
+
+		err = dm_i2c_reg_write(dev, ABX8XX_REG_OUT_CTRL,
+				       data | ABX8XX_OUT_CTRL_EXDS);
+		if (err < 0) {
+			log_err("Unable to write output control register\n");
+			return -EIO;
+		}
+	}
+
+	/* part autodetection */
+	if (part == ABX80X) {
+		for (i = 0; abx80x_caps[i].pn; i++)
+			if (partnumber == abx80x_caps[i].pn)
+				break;
+		if (abx80x_caps[i].pn == 0) {
+			log_err("Unknown part: %04x\n", partnumber);
+			return -EINVAL;
+		}
+		part = i;
+	}
+
+	if (partnumber != abx80x_caps[part].pn) {
+		log_err("partnumber mismatch %04x != %04x\n",
+			partnumber, abx80x_caps[part].pn);
+		return -EINVAL;
+	}
+
+	if (abx80x_caps[part].has_tc)
+		trickle_cfg = abx80x_dt_trickle_cfg(dev);
+
+	if (trickle_cfg > 0) {
+		log_debug("Enabling trickle charger: %02x\n", trickle_cfg);
+		abx80x_enable_trickle_charger(dev, trickle_cfg);
+	}
+
+	err = dm_i2c_reg_write(dev, ABX8XX_REG_CD_TIMER_CTL, BIT(2));
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static const struct udevice_id abx80x_of_match[] = {
+	{
+		.compatible = "abracon,abx80x",
+		.data = ABX80X
+	},
+	{
+		.compatible = "abracon,ab0801",
+		.data = AB0801
+	},
+	{
+		.compatible = "abracon,ab0803",
+		.data = AB0803
+	},
+	{
+		.compatible = "abracon,ab0804",
+		.data = AB0804
+	},
+	{
+		.compatible = "abracon,ab0805",
+		.data = AB0805
+	},
+	{
+		.compatible = "abracon,ab1801",
+		.data = AB1801
+	},
+	{
+		.compatible = "abracon,ab1803",
+		.data = AB1803
+	},
+	{
+		.compatible = "abracon,ab1804",
+		.data = AB1804
+	},
+	{
+		.compatible = "abracon,ab1805",
+		.data = AB1805
+	},
+	{
+		.compatible = "microcrystal,rv1805",
+		.data = RV1805
+	},
+	{ }
+};
+
+U_BOOT_DRIVER(abx80x_rtc) = {
+	.name	= "rtc-abx80x",
+	.id     = UCLASS_RTC,
+	.probe		= abx80x_probe,
+	.of_match = abx80x_of_match,
+	.ops = &abx80x_rtc_ops,
+};