Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 935 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-rs5c372.c b/drivers/rtc/rtc-rs5c372.c
new file mode 100644
index 000000000..9562c477e
--- /dev/null
+++ b/drivers/rtc/rtc-rs5c372.c
@@ -0,0 +1,935 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * An I2C driver for Ricoh RS5C372, R2025S/D and RV5C38[67] RTCs
+ *
+ * Copyright (C) 2005 Pavel Mironchik <pmironchik@optifacio.net>
+ * Copyright (C) 2006 Tower Technologies
+ * Copyright (C) 2008 Paul Mundt
+ */
+
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+
+/*
+ * Ricoh has a family of I2C based RTCs, which differ only slightly from
+ * each other.  Differences center on pinout (e.g. how many interrupts,
+ * output clock, etc) and how the control registers are used.  The '372
+ * is significant only because that's the one this driver first supported.
+ */
+#define RS5C372_REG_SECS	0
+#define RS5C372_REG_MINS	1
+#define RS5C372_REG_HOURS	2
+#define RS5C372_REG_WDAY	3
+#define RS5C372_REG_DAY		4
+#define RS5C372_REG_MONTH	5
+#define RS5C372_REG_YEAR	6
+#define RS5C372_REG_TRIM	7
+#	define RS5C372_TRIM_XSL		0x80		/* only if RS5C372[a|b] */
+#	define RS5C372_TRIM_MASK	0x7F
+#	define R2221TL_TRIM_DEV		(1 << 7)	/* only if R2221TL */
+#	define RS5C372_TRIM_DECR	(1 << 6)
+
+#define RS5C_REG_ALARM_A_MIN	8			/* or ALARM_W */
+#define RS5C_REG_ALARM_A_HOURS	9
+#define RS5C_REG_ALARM_A_WDAY	10
+
+#define RS5C_REG_ALARM_B_MIN	11			/* or ALARM_D */
+#define RS5C_REG_ALARM_B_HOURS	12
+#define RS5C_REG_ALARM_B_WDAY	13			/* (ALARM_B only) */
+
+#define RS5C_REG_CTRL1		14
+#	define RS5C_CTRL1_AALE		(1 << 7)	/* or WALE */
+#	define RS5C_CTRL1_BALE		(1 << 6)	/* or DALE */
+#	define RV5C387_CTRL1_24		(1 << 5)
+#	define RS5C372A_CTRL1_SL1	(1 << 5)
+#	define RS5C_CTRL1_CT_MASK	(7 << 0)
+#	define RS5C_CTRL1_CT0		(0 << 0)	/* no periodic irq */
+#	define RS5C_CTRL1_CT4		(4 << 0)	/* 1 Hz level irq */
+#define RS5C_REG_CTRL2		15
+#	define RS5C372_CTRL2_24		(1 << 5)
+#	define RS5C_CTRL2_XSTP		(1 << 4)	/* only if !R2x2x */
+#	define R2x2x_CTRL2_VDET		(1 << 6)	/* only if  R2x2x */
+#	define R2x2x_CTRL2_XSTP		(1 << 5)	/* only if  R2x2x */
+#	define R2x2x_CTRL2_PON		(1 << 4)	/* only if  R2x2x */
+#	define RS5C_CTRL2_CTFG		(1 << 2)
+#	define RS5C_CTRL2_AAFG		(1 << 1)	/* or WAFG */
+#	define RS5C_CTRL2_BAFG		(1 << 0)	/* or DAFG */
+
+
+/* to read (style 1) or write registers starting at R */
+#define RS5C_ADDR(R)		(((R) << 4) | 0)
+
+
+enum rtc_type {
+	rtc_undef = 0,
+	rtc_r2025sd,
+	rtc_r2221tl,
+	rtc_rs5c372a,
+	rtc_rs5c372b,
+	rtc_rv5c386,
+	rtc_rv5c387a,
+};
+
+static const struct i2c_device_id rs5c372_id[] = {
+	{ "r2025sd", rtc_r2025sd },
+	{ "r2221tl", rtc_r2221tl },
+	{ "rs5c372a", rtc_rs5c372a },
+	{ "rs5c372b", rtc_rs5c372b },
+	{ "rv5c386", rtc_rv5c386 },
+	{ "rv5c387a", rtc_rv5c387a },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, rs5c372_id);
+
+static const __maybe_unused struct of_device_id rs5c372_of_match[] = {
+	{
+		.compatible = "ricoh,r2025sd",
+		.data = (void *)rtc_r2025sd
+	},
+	{
+		.compatible = "ricoh,r2221tl",
+		.data = (void *)rtc_r2221tl
+	},
+	{
+		.compatible = "ricoh,rs5c372a",
+		.data = (void *)rtc_rs5c372a
+	},
+	{
+		.compatible = "ricoh,rs5c372b",
+		.data = (void *)rtc_rs5c372b
+	},
+	{
+		.compatible = "ricoh,rv5c386",
+		.data = (void *)rtc_rv5c386
+	},
+	{
+		.compatible = "ricoh,rv5c387a",
+		.data = (void *)rtc_rv5c387a
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, rs5c372_of_match);
+
+/* REVISIT:  this assumes that:
+ *  - we're in the 21st century, so it's safe to ignore the century
+ *    bit for rv5c38[67] (REG_MONTH bit 7);
+ *  - we should use ALARM_A not ALARM_B (may be wrong on some boards)
+ */
+struct rs5c372 {
+	struct i2c_client	*client;
+	struct rtc_device	*rtc;
+	enum rtc_type		type;
+	unsigned		time24:1;
+	unsigned		has_irq:1;
+	unsigned		smbus:1;
+	char			buf[17];
+	char			*regs;
+};
+
+static int rs5c_get_regs(struct rs5c372 *rs5c)
+{
+	struct i2c_client	*client = rs5c->client;
+	struct i2c_msg		msgs[] = {
+		{
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = sizeof(rs5c->buf),
+			.buf = rs5c->buf
+		},
+	};
+
+	/* This implements the third reading method from the datasheet, using
+	 * an internal address that's reset after each transaction (by STOP)
+	 * to 0x0f ... so we read extra registers, and skip the first one.
+	 *
+	 * The first method doesn't work with the iop3xx adapter driver, on at
+	 * least 80219 chips; this works around that bug.
+	 *
+	 * The third method on the other hand doesn't work for the SMBus-only
+	 * configurations, so we use the the first method there, stripping off
+	 * the extra register in the process.
+	 */
+	if (rs5c->smbus) {
+		int addr = RS5C_ADDR(RS5C372_REG_SECS);
+		int size = sizeof(rs5c->buf) - 1;
+
+		if (i2c_smbus_read_i2c_block_data(client, addr, size,
+						  rs5c->buf + 1) != size) {
+			dev_warn(&client->dev, "can't read registers\n");
+			return -EIO;
+		}
+	} else {
+		if ((i2c_transfer(client->adapter, msgs, 1)) != 1) {
+			dev_warn(&client->dev, "can't read registers\n");
+			return -EIO;
+		}
+	}
+
+	dev_dbg(&client->dev,
+		"%3ph (%02x) %3ph (%02x), %3ph, %3ph; %02x %02x\n",
+		rs5c->regs + 0, rs5c->regs[3],
+		rs5c->regs + 4, rs5c->regs[7],
+		rs5c->regs + 8, rs5c->regs + 11,
+		rs5c->regs[14], rs5c->regs[15]);
+
+	return 0;
+}
+
+static unsigned rs5c_reg2hr(struct rs5c372 *rs5c, unsigned reg)
+{
+	unsigned	hour;
+
+	if (rs5c->time24)
+		return bcd2bin(reg & 0x3f);
+
+	hour = bcd2bin(reg & 0x1f);
+	if (hour == 12)
+		hour = 0;
+	if (reg & 0x20)
+		hour += 12;
+	return hour;
+}
+
+static unsigned rs5c_hr2reg(struct rs5c372 *rs5c, unsigned hour)
+{
+	if (rs5c->time24)
+		return bin2bcd(hour);
+
+	if (hour > 12)
+		return 0x20 | bin2bcd(hour - 12);
+	if (hour == 12)
+		return 0x20 | bin2bcd(12);
+	if (hour == 0)
+		return bin2bcd(12);
+	return bin2bcd(hour);
+}
+
+static int rs5c372_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct rs5c372	*rs5c = i2c_get_clientdata(client);
+	int		status = rs5c_get_regs(rs5c);
+	unsigned char ctrl2 = rs5c->regs[RS5C_REG_CTRL2];
+
+	if (status < 0)
+		return status;
+
+	switch (rs5c->type) {
+	case rtc_r2025sd:
+	case rtc_r2221tl:
+		if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
+		    (rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
+			dev_warn(&client->dev, "rtc oscillator interruption detected. Please reset the rtc clock.\n");
+			return -EINVAL;
+		}
+		break;
+	default:
+		if (ctrl2 & RS5C_CTRL2_XSTP) {
+			dev_warn(&client->dev, "rtc oscillator interruption detected. Please reset the rtc clock.\n");
+			return -EINVAL;
+		}
+	}
+
+	tm->tm_sec = bcd2bin(rs5c->regs[RS5C372_REG_SECS] & 0x7f);
+	tm->tm_min = bcd2bin(rs5c->regs[RS5C372_REG_MINS] & 0x7f);
+	tm->tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C372_REG_HOURS]);
+
+	tm->tm_wday = bcd2bin(rs5c->regs[RS5C372_REG_WDAY] & 0x07);
+	tm->tm_mday = bcd2bin(rs5c->regs[RS5C372_REG_DAY] & 0x3f);
+
+	/* tm->tm_mon is zero-based */
+	tm->tm_mon = bcd2bin(rs5c->regs[RS5C372_REG_MONTH] & 0x1f) - 1;
+
+	/* year is 1900 + tm->tm_year */
+	tm->tm_year = bcd2bin(rs5c->regs[RS5C372_REG_YEAR]) + 100;
+
+	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
+		"mday=%d, mon=%d, year=%d, wday=%d\n",
+		__func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
+
+	return 0;
+}
+
+static int rs5c372_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct rs5c372	*rs5c = i2c_get_clientdata(client);
+	unsigned char	buf[7];
+	unsigned char	ctrl2;
+	int		addr;
+
+	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d "
+		"mday=%d, mon=%d, year=%d, wday=%d\n",
+		__func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
+
+	addr   = RS5C_ADDR(RS5C372_REG_SECS);
+	buf[0] = bin2bcd(tm->tm_sec);
+	buf[1] = bin2bcd(tm->tm_min);
+	buf[2] = rs5c_hr2reg(rs5c, tm->tm_hour);
+	buf[3] = bin2bcd(tm->tm_wday);
+	buf[4] = bin2bcd(tm->tm_mday);
+	buf[5] = bin2bcd(tm->tm_mon + 1);
+	buf[6] = bin2bcd(tm->tm_year - 100);
+
+	if (i2c_smbus_write_i2c_block_data(client, addr, sizeof(buf), buf) < 0) {
+		dev_dbg(&client->dev, "%s: write error in line %i\n",
+			__func__, __LINE__);
+		return -EIO;
+	}
+
+	addr = RS5C_ADDR(RS5C_REG_CTRL2);
+	ctrl2 = i2c_smbus_read_byte_data(client, addr);
+
+	/* clear rtc warning bits */
+	switch (rs5c->type) {
+	case rtc_r2025sd:
+	case rtc_r2221tl:
+		ctrl2 &= ~(R2x2x_CTRL2_VDET | R2x2x_CTRL2_PON);
+		if (rs5c->type == rtc_r2025sd)
+			ctrl2 |= R2x2x_CTRL2_XSTP;
+		else
+			ctrl2 &= ~R2x2x_CTRL2_XSTP;
+		break;
+	default:
+		ctrl2 &= ~RS5C_CTRL2_XSTP;
+		break;
+	}
+
+	if (i2c_smbus_write_byte_data(client, addr, ctrl2) < 0) {
+		dev_dbg(&client->dev, "%s: write error in line %i\n",
+			__func__, __LINE__);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_RTC_INTF_PROC)
+#define	NEED_TRIM
+#endif
+
+#if IS_ENABLED(CONFIG_RTC_INTF_SYSFS)
+#define	NEED_TRIM
+#endif
+
+#ifdef	NEED_TRIM
+static int rs5c372_get_trim(struct i2c_client *client, int *osc, int *trim)
+{
+	struct rs5c372 *rs5c372 = i2c_get_clientdata(client);
+	u8 tmp = rs5c372->regs[RS5C372_REG_TRIM];
+
+	if (osc) {
+		if (rs5c372->type == rtc_rs5c372a || rs5c372->type == rtc_rs5c372b)
+			*osc = (tmp & RS5C372_TRIM_XSL) ? 32000 : 32768;
+		else
+			*osc = 32768;
+	}
+
+	if (trim) {
+		dev_dbg(&client->dev, "%s: raw trim=%x\n", __func__, tmp);
+		tmp &= RS5C372_TRIM_MASK;
+		if (tmp & 0x3e) {
+			int t = tmp & 0x3f;
+
+			if (tmp & 0x40)
+				t = (~t | (s8)0xc0) + 1;
+			else
+				t = t - 1;
+
+			tmp = t * 2;
+		} else
+			tmp = 0;
+		*trim = tmp;
+	}
+
+	return 0;
+}
+#endif
+
+static int rs5c_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct i2c_client	*client = to_i2c_client(dev);
+	struct rs5c372		*rs5c = i2c_get_clientdata(client);
+	unsigned char		buf;
+	int			status, addr;
+
+	buf = rs5c->regs[RS5C_REG_CTRL1];
+
+	if (!rs5c->has_irq)
+		return -EINVAL;
+
+	status = rs5c_get_regs(rs5c);
+	if (status < 0)
+		return status;
+
+	addr = RS5C_ADDR(RS5C_REG_CTRL1);
+	if (enabled)
+		buf |= RS5C_CTRL1_AALE;
+	else
+		buf &= ~RS5C_CTRL1_AALE;
+
+	if (i2c_smbus_write_byte_data(client, addr, buf) < 0) {
+		dev_warn(dev, "can't update alarm\n");
+		status = -EIO;
+	} else
+		rs5c->regs[RS5C_REG_CTRL1] = buf;
+
+	return status;
+}
+
+
+/* NOTE:  Since RTC_WKALM_{RD,SET} were originally defined for EFI,
+ * which only exposes a polled programming interface; and since
+ * these calls map directly to those EFI requests; we don't demand
+ * we have an IRQ for this chip when we go through this API.
+ *
+ * The older x86_pc derived RTC_ALM_{READ,SET} calls require irqs
+ * though, managed through RTC_AIE_{ON,OFF} requests.
+ */
+
+static int rs5c_read_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct i2c_client	*client = to_i2c_client(dev);
+	struct rs5c372		*rs5c = i2c_get_clientdata(client);
+	int			status;
+
+	status = rs5c_get_regs(rs5c);
+	if (status < 0)
+		return status;
+
+	/* report alarm time */
+	t->time.tm_sec = 0;
+	t->time.tm_min = bcd2bin(rs5c->regs[RS5C_REG_ALARM_A_MIN] & 0x7f);
+	t->time.tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C_REG_ALARM_A_HOURS]);
+
+	/* ... and status */
+	t->enabled = !!(rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE);
+	t->pending = !!(rs5c->regs[RS5C_REG_CTRL2] & RS5C_CTRL2_AAFG);
+
+	return 0;
+}
+
+static int rs5c_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct i2c_client	*client = to_i2c_client(dev);
+	struct rs5c372		*rs5c = i2c_get_clientdata(client);
+	int			status, addr, i;
+	unsigned char		buf[3];
+
+	/* only handle up to 24 hours in the future, like RTC_ALM_SET */
+	if (t->time.tm_mday != -1
+			|| t->time.tm_mon != -1
+			|| t->time.tm_year != -1)
+		return -EINVAL;
+
+	/* REVISIT: round up tm_sec */
+
+	/* if needed, disable irq (clears pending status) */
+	status = rs5c_get_regs(rs5c);
+	if (status < 0)
+		return status;
+	if (rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE) {
+		addr = RS5C_ADDR(RS5C_REG_CTRL1);
+		buf[0] = rs5c->regs[RS5C_REG_CTRL1] & ~RS5C_CTRL1_AALE;
+		if (i2c_smbus_write_byte_data(client, addr, buf[0]) < 0) {
+			dev_dbg(dev, "can't disable alarm\n");
+			return -EIO;
+		}
+		rs5c->regs[RS5C_REG_CTRL1] = buf[0];
+	}
+
+	/* set alarm */
+	buf[0] = bin2bcd(t->time.tm_min);
+	buf[1] = rs5c_hr2reg(rs5c, t->time.tm_hour);
+	buf[2] = 0x7f;	/* any/all days */
+
+	for (i = 0; i < sizeof(buf); i++) {
+		addr = RS5C_ADDR(RS5C_REG_ALARM_A_MIN + i);
+		if (i2c_smbus_write_byte_data(client, addr, buf[i]) < 0) {
+			dev_dbg(dev, "can't set alarm time\n");
+			return -EIO;
+		}
+	}
+
+	/* ... and maybe enable its irq */
+	if (t->enabled) {
+		addr = RS5C_ADDR(RS5C_REG_CTRL1);
+		buf[0] = rs5c->regs[RS5C_REG_CTRL1] | RS5C_CTRL1_AALE;
+		if (i2c_smbus_write_byte_data(client, addr, buf[0]) < 0)
+			dev_warn(dev, "can't enable alarm\n");
+		rs5c->regs[RS5C_REG_CTRL1] = buf[0];
+	}
+
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_RTC_INTF_PROC)
+
+static int rs5c372_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+	int err, osc, trim;
+
+	err = rs5c372_get_trim(to_i2c_client(dev), &osc, &trim);
+	if (err == 0) {
+		seq_printf(seq, "crystal\t\t: %d.%03d KHz\n",
+				osc / 1000, osc % 1000);
+		seq_printf(seq, "trim\t\t: %d\n", trim);
+	}
+
+	return 0;
+}
+
+#else
+#define	rs5c372_rtc_proc	NULL
+#endif
+
+#ifdef CONFIG_RTC_INTF_DEV
+static int rs5c372_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct rs5c372	*rs5c = i2c_get_clientdata(to_i2c_client(dev));
+	unsigned char	ctrl2;
+	int		addr;
+	unsigned int	flags;
+
+	dev_dbg(dev, "%s: cmd=%x\n", __func__, cmd);
+
+	addr = RS5C_ADDR(RS5C_REG_CTRL2);
+	ctrl2 = i2c_smbus_read_byte_data(rs5c->client, addr);
+
+	switch (cmd) {
+	case RTC_VL_READ:
+		flags = 0;
+
+		switch (rs5c->type) {
+		case rtc_r2025sd:
+		case rtc_r2221tl:
+			if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
+				(rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
+				flags |= RTC_VL_DATA_INVALID;
+			}
+			if (ctrl2 & R2x2x_CTRL2_VDET)
+				flags |= RTC_VL_BACKUP_LOW;
+			break;
+		default:
+			if (ctrl2 & RS5C_CTRL2_XSTP)
+				flags |= RTC_VL_DATA_INVALID;
+			break;
+		}
+
+		return put_user(flags, (unsigned int __user *)arg);
+	case RTC_VL_CLR:
+		/* clear VDET bit */
+		if (rs5c->type == rtc_r2025sd || rs5c->type == rtc_r2221tl) {
+			ctrl2 &= ~R2x2x_CTRL2_VDET;
+			if (i2c_smbus_write_byte_data(rs5c->client, addr, ctrl2) < 0) {
+				dev_dbg(&rs5c->client->dev, "%s: write error in line %i\n",
+						__func__, __LINE__);
+				return -EIO;
+			}
+		}
+		return 0;
+	default:
+		return -ENOIOCTLCMD;
+	}
+	return 0;
+}
+#else
+#define rs5c372_ioctl	NULL
+#endif
+
+static int rs5c372_read_offset(struct device *dev, long *offset)
+{
+	struct rs5c372 *rs5c = i2c_get_clientdata(to_i2c_client(dev));
+	u8 val = rs5c->regs[RS5C372_REG_TRIM];
+	long ppb_per_step = 0;
+	bool decr = val & RS5C372_TRIM_DECR;
+
+	switch (rs5c->type) {
+	case rtc_r2221tl:
+		ppb_per_step = val & R2221TL_TRIM_DEV ? 1017 : 3051;
+		break;
+	case rtc_rs5c372a:
+	case rtc_rs5c372b:
+		ppb_per_step = val & RS5C372_TRIM_XSL ? 3125 : 3051;
+		break;
+	default:
+		ppb_per_step = 3051;
+		break;
+	}
+
+	/* Only bits[0:5] repsents the time counts */
+	val &= 0x3F;
+
+	/* If bits[1:5] are all 0, it means no increment or decrement */
+	if (!(val & 0x3E)) {
+		*offset = 0;
+	} else {
+		if (decr)
+			*offset = -(((~val) & 0x3F) + 1) * ppb_per_step;
+		else
+			*offset = (val - 1) * ppb_per_step;
+	}
+
+	return 0;
+}
+
+static int rs5c372_set_offset(struct device *dev, long offset)
+{
+	struct rs5c372 *rs5c = i2c_get_clientdata(to_i2c_client(dev));
+	int addr = RS5C_ADDR(RS5C372_REG_TRIM);
+	u8 val = 0;
+	u8 tmp = 0;
+	long ppb_per_step = 3051;
+	long steps = LONG_MIN;
+
+	switch (rs5c->type) {
+	case rtc_rs5c372a:
+	case rtc_rs5c372b:
+		tmp = rs5c->regs[RS5C372_REG_TRIM];
+		if (tmp & RS5C372_TRIM_XSL) {
+			ppb_per_step = 3125;
+			val |= RS5C372_TRIM_XSL;
+		}
+		break;
+	case rtc_r2221tl:
+		/*
+		 * Check if it is possible to use high resolution mode (DEV=1).
+		 * In this mode, the minimum resolution is 2 / (32768 * 20 * 3),
+		 * which is about 1017 ppb.
+		 */
+		steps = DIV_ROUND_CLOSEST(offset, 1017);
+		if (steps >= -0x3E && steps <= 0x3E) {
+			ppb_per_step = 1017;
+			val |= R2221TL_TRIM_DEV;
+		} else {
+			/*
+			 * offset is out of the range of high resolution mode.
+			 * Try to use low resolution mode (DEV=0). In this mode,
+			 * the minimum resolution is 2 / (32768 * 20), which is
+			 * about 3051 ppb.
+			 */
+			steps = LONG_MIN;
+		}
+		break;
+	default:
+		break;
+	}
+
+	if (steps == LONG_MIN) {
+		steps = DIV_ROUND_CLOSEST(offset, ppb_per_step);
+		if (steps > 0x3E || steps < -0x3E)
+			return -ERANGE;
+	}
+
+	if (steps > 0) {
+		val |= steps + 1;
+	} else {
+		val |= RS5C372_TRIM_DECR;
+		val |= (~(-steps - 1)) & 0x3F;
+	}
+
+	if (!steps || !(val & 0x3E)) {
+		/*
+		 * if offset is too small, set oscillation adjustment register
+		 * or time trimming register with its default value whic means
+		 * no increment or decrement. But for rs5c372[a|b], the XSL bit
+		 * should be kept unchanged.
+		 */
+		if (rs5c->type == rtc_rs5c372a || rs5c->type == rtc_rs5c372b)
+			val &= RS5C372_TRIM_XSL;
+		else
+			val = 0;
+	}
+
+	dev_dbg(&rs5c->client->dev, "write 0x%x for offset %ld\n", val, offset);
+
+	if (i2c_smbus_write_byte_data(rs5c->client, addr, val) < 0) {
+		dev_err(&rs5c->client->dev, "failed to write 0x%x to reg %d\n", val, addr);
+		return -EIO;
+	}
+
+	rs5c->regs[RS5C372_REG_TRIM] = val;
+
+	return 0;
+}
+
+static const struct rtc_class_ops rs5c372_rtc_ops = {
+	.proc		= rs5c372_rtc_proc,
+	.read_time	= rs5c372_rtc_read_time,
+	.set_time	= rs5c372_rtc_set_time,
+	.read_alarm	= rs5c_read_alarm,
+	.set_alarm	= rs5c_set_alarm,
+	.alarm_irq_enable = rs5c_rtc_alarm_irq_enable,
+	.ioctl		= rs5c372_ioctl,
+	.read_offset    = rs5c372_read_offset,
+	.set_offset     = rs5c372_set_offset,
+};
+
+#if IS_ENABLED(CONFIG_RTC_INTF_SYSFS)
+
+static ssize_t rs5c372_sysfs_show_trim(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int err, trim;
+
+	err = rs5c372_get_trim(to_i2c_client(dev), NULL, &trim);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d\n", trim);
+}
+static DEVICE_ATTR(trim, S_IRUGO, rs5c372_sysfs_show_trim, NULL);
+
+static ssize_t rs5c372_sysfs_show_osc(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int err, osc;
+
+	err = rs5c372_get_trim(to_i2c_client(dev), &osc, NULL);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d.%03d KHz\n", osc / 1000, osc % 1000);
+}
+static DEVICE_ATTR(osc, S_IRUGO, rs5c372_sysfs_show_osc, NULL);
+
+static int rs5c_sysfs_register(struct device *dev)
+{
+	int err;
+
+	err = device_create_file(dev, &dev_attr_trim);
+	if (err)
+		return err;
+	err = device_create_file(dev, &dev_attr_osc);
+	if (err)
+		device_remove_file(dev, &dev_attr_trim);
+
+	return err;
+}
+
+static void rs5c_sysfs_unregister(struct device *dev)
+{
+	device_remove_file(dev, &dev_attr_trim);
+	device_remove_file(dev, &dev_attr_osc);
+}
+
+#else
+static int rs5c_sysfs_register(struct device *dev)
+{
+	return 0;
+}
+
+static void rs5c_sysfs_unregister(struct device *dev)
+{
+	/* nothing */
+}
+#endif	/* SYSFS */
+
+static struct i2c_driver rs5c372_driver;
+
+static int rs5c_oscillator_setup(struct rs5c372 *rs5c372)
+{
+	unsigned char buf[2];
+	int addr, i, ret = 0;
+
+	addr   = RS5C_ADDR(RS5C_REG_CTRL1);
+	buf[0] = rs5c372->regs[RS5C_REG_CTRL1];
+	buf[1] = rs5c372->regs[RS5C_REG_CTRL2];
+
+	switch (rs5c372->type) {
+	case rtc_r2025sd:
+		if (buf[1] & R2x2x_CTRL2_XSTP)
+			return ret;
+		break;
+	case rtc_r2221tl:
+		if (!(buf[1] & R2x2x_CTRL2_XSTP))
+			return ret;
+		break;
+	default:
+		if (!(buf[1] & RS5C_CTRL2_XSTP))
+			return ret;
+		break;
+	}
+
+	/* use 24hr mode */
+	switch (rs5c372->type) {
+	case rtc_rs5c372a:
+	case rtc_rs5c372b:
+		buf[1] |= RS5C372_CTRL2_24;
+		rs5c372->time24 = 1;
+		break;
+	case rtc_r2025sd:
+	case rtc_r2221tl:
+	case rtc_rv5c386:
+	case rtc_rv5c387a:
+		buf[0] |= RV5C387_CTRL1_24;
+		rs5c372->time24 = 1;
+		break;
+	default:
+		/* impossible */
+		break;
+	}
+
+	for (i = 0; i < sizeof(buf); i++) {
+		addr = RS5C_ADDR(RS5C_REG_CTRL1 + i);
+		ret = i2c_smbus_write_byte_data(rs5c372->client, addr, buf[i]);
+		if (unlikely(ret < 0))
+			return ret;
+	}
+
+	rs5c372->regs[RS5C_REG_CTRL1] = buf[0];
+	rs5c372->regs[RS5C_REG_CTRL2] = buf[1];
+
+	return 0;
+}
+
+static int rs5c372_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	int err = 0;
+	int smbus_mode = 0;
+	struct rs5c372 *rs5c372;
+
+	dev_dbg(&client->dev, "%s\n", __func__);
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
+			I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK)) {
+		/*
+		 * If we don't have any master mode adapter, try breaking
+		 * it down in to the barest of capabilities.
+		 */
+		if (i2c_check_functionality(client->adapter,
+				I2C_FUNC_SMBUS_BYTE_DATA |
+				I2C_FUNC_SMBUS_I2C_BLOCK))
+			smbus_mode = 1;
+		else {
+			/* Still no good, give up */
+			err = -ENODEV;
+			goto exit;
+		}
+	}
+
+	rs5c372 = devm_kzalloc(&client->dev, sizeof(struct rs5c372),
+				GFP_KERNEL);
+	if (!rs5c372) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	rs5c372->client = client;
+	i2c_set_clientdata(client, rs5c372);
+	if (client->dev.of_node)
+		rs5c372->type = (enum rtc_type)
+			of_device_get_match_data(&client->dev);
+	else
+		rs5c372->type = id->driver_data;
+
+	/* we read registers 0x0f then 0x00-0x0f; skip the first one */
+	rs5c372->regs = &rs5c372->buf[1];
+	rs5c372->smbus = smbus_mode;
+
+	err = rs5c_get_regs(rs5c372);
+	if (err < 0)
+		goto exit;
+
+	/* clock may be set for am/pm or 24 hr time */
+	switch (rs5c372->type) {
+	case rtc_rs5c372a:
+	case rtc_rs5c372b:
+		/* alarm uses ALARM_A; and nINTRA on 372a, nINTR on 372b.
+		 * so does periodic irq, except some 327a modes.
+		 */
+		if (rs5c372->regs[RS5C_REG_CTRL2] & RS5C372_CTRL2_24)
+			rs5c372->time24 = 1;
+		break;
+	case rtc_r2025sd:
+	case rtc_r2221tl:
+	case rtc_rv5c386:
+	case rtc_rv5c387a:
+		if (rs5c372->regs[RS5C_REG_CTRL1] & RV5C387_CTRL1_24)
+			rs5c372->time24 = 1;
+		/* alarm uses ALARM_W; and nINTRB for alarm and periodic
+		 * irq, on both 386 and 387
+		 */
+		break;
+	default:
+		dev_err(&client->dev, "unknown RTC type\n");
+		goto exit;
+	}
+
+	/* if the oscillator lost power and no other software (like
+	 * the bootloader) set it up, do it here.
+	 *
+	 * The R2025S/D does this a little differently than the other
+	 * parts, so we special case that..
+	 */
+	err = rs5c_oscillator_setup(rs5c372);
+	if (unlikely(err < 0)) {
+		dev_err(&client->dev, "setup error\n");
+		goto exit;
+	}
+
+	dev_info(&client->dev, "%s found, %s\n",
+			({ char *s; switch (rs5c372->type) {
+			case rtc_r2025sd:	s = "r2025sd"; break;
+			case rtc_r2221tl:	s = "r2221tl"; break;
+			case rtc_rs5c372a:	s = "rs5c372a"; break;
+			case rtc_rs5c372b:	s = "rs5c372b"; break;
+			case rtc_rv5c386:	s = "rv5c386"; break;
+			case rtc_rv5c387a:	s = "rv5c387a"; break;
+			default:		s = "chip"; break;
+			}; s;}),
+			rs5c372->time24 ? "24hr" : "am/pm"
+			);
+
+	/* REVISIT use client->irq to register alarm irq ... */
+	rs5c372->rtc = devm_rtc_device_register(&client->dev,
+					rs5c372_driver.driver.name,
+					&rs5c372_rtc_ops, THIS_MODULE);
+
+	if (IS_ERR(rs5c372->rtc)) {
+		err = PTR_ERR(rs5c372->rtc);
+		goto exit;
+	}
+
+	err = rs5c_sysfs_register(&client->dev);
+	if (err)
+		goto exit;
+
+	return 0;
+
+exit:
+	return err;
+}
+
+static void rs5c372_remove(struct i2c_client *client)
+{
+	rs5c_sysfs_unregister(&client->dev);
+}
+
+static struct i2c_driver rs5c372_driver = {
+	.driver		= {
+		.name	= "rtc-rs5c372",
+		.of_match_table = of_match_ptr(rs5c372_of_match),
+	},
+	.probe		= rs5c372_probe,
+	.remove		= rs5c372_remove,
+	.id_table	= rs5c372_id,
+};
+
+module_i2c_driver(rs5c372_driver);
+
+MODULE_AUTHOR(
+		"Pavel Mironchik <pmironchik@optifacio.net>, "
+		"Alessandro Zummo <a.zummo@towertech.it>, "
+		"Paul Mundt <lethal@linux-sh.org>");
+MODULE_DESCRIPTION("Ricoh RS5C372 RTC driver");
+MODULE_LICENSE("GPL");