Adding upstream version 5.10.209.upstream/5.10.209

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

1 files changed, 913 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-isl1208.c b/drivers/rtc/rtc-isl1208.c
new file mode 100644
index 000000000..ebb691fa4
--- /dev/null
+++ b/drivers/rtc/rtc-isl1208.c
@@ -0,0 +1,913 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Intersil ISL1208 rtc class driver
+ *
+ * Copyright 2005,2006 Hebert Valerio Riedel <hvr@gnu.org>
+ */
+
+#include <linux/bcd.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/rtc.h>
+
+/* Register map */
+/* rtc section */
+#define ISL1208_REG_SC  0x00
+#define ISL1208_REG_MN  0x01
+#define ISL1208_REG_HR  0x02
+#define ISL1208_REG_HR_MIL     (1<<7)	/* 24h/12h mode */
+#define ISL1208_REG_HR_PM      (1<<5)	/* PM/AM bit in 12h mode */
+#define ISL1208_REG_DT  0x03
+#define ISL1208_REG_MO  0x04
+#define ISL1208_REG_YR  0x05
+#define ISL1208_REG_DW  0x06
+#define ISL1208_RTC_SECTION_LEN 7
+
+/* control/status section */
+#define ISL1208_REG_SR  0x07
+#define ISL1208_REG_SR_ARST    (1<<7)	/* auto reset */
+#define ISL1208_REG_SR_XTOSCB  (1<<6)	/* crystal oscillator */
+#define ISL1208_REG_SR_WRTC    (1<<4)	/* write rtc */
+#define ISL1208_REG_SR_EVT     (1<<3)	/* event */
+#define ISL1208_REG_SR_ALM     (1<<2)	/* alarm */
+#define ISL1208_REG_SR_BAT     (1<<1)	/* battery */
+#define ISL1208_REG_SR_RTCF    (1<<0)	/* rtc fail */
+#define ISL1208_REG_INT 0x08
+#define ISL1208_REG_INT_ALME   (1<<6)   /* alarm enable */
+#define ISL1208_REG_INT_IM     (1<<7)   /* interrupt/alarm mode */
+#define ISL1219_REG_EV  0x09
+#define ISL1219_REG_EV_EVEN    (1<<4)   /* event detection enable */
+#define ISL1219_REG_EV_EVIENB  (1<<7)   /* event in pull-up disable */
+#define ISL1208_REG_ATR 0x0a
+#define ISL1208_REG_DTR 0x0b
+
+/* alarm section */
+#define ISL1208_REG_SCA 0x0c
+#define ISL1208_REG_MNA 0x0d
+#define ISL1208_REG_HRA 0x0e
+#define ISL1208_REG_DTA 0x0f
+#define ISL1208_REG_MOA 0x10
+#define ISL1208_REG_DWA 0x11
+#define ISL1208_ALARM_SECTION_LEN 6
+
+/* user section */
+#define ISL1208_REG_USR1 0x12
+#define ISL1208_REG_USR2 0x13
+#define ISL1208_USR_SECTION_LEN 2
+
+/* event section */
+#define ISL1219_REG_SCT 0x14
+#define ISL1219_REG_MNT 0x15
+#define ISL1219_REG_HRT 0x16
+#define ISL1219_REG_DTT 0x17
+#define ISL1219_REG_MOT 0x18
+#define ISL1219_REG_YRT 0x19
+#define ISL1219_EVT_SECTION_LEN 6
+
+static struct i2c_driver isl1208_driver;
+
+/* ISL1208 various variants */
+enum isl1208_id {
+	TYPE_ISL1208 = 0,
+	TYPE_ISL1209,
+	TYPE_ISL1218,
+	TYPE_ISL1219,
+	ISL_LAST_ID
+};
+
+/* Chip capabilities table */
+static const struct isl1208_config {
+	const char	name[8];
+	unsigned int	nvmem_length;
+	unsigned	has_tamper:1;
+	unsigned	has_timestamp:1;
+} isl1208_configs[] = {
+	[TYPE_ISL1208] = { "isl1208", 2, false, false },
+	[TYPE_ISL1209] = { "isl1209", 2, true,  false },
+	[TYPE_ISL1218] = { "isl1218", 8, false, false },
+	[TYPE_ISL1219] = { "isl1219", 2, true,  true },
+};
+
+static const struct i2c_device_id isl1208_id[] = {
+	{ "isl1208", TYPE_ISL1208 },
+	{ "isl1209", TYPE_ISL1209 },
+	{ "isl1218", TYPE_ISL1218 },
+	{ "isl1219", TYPE_ISL1219 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, isl1208_id);
+
+static const struct of_device_id isl1208_of_match[] = {
+	{ .compatible = "isil,isl1208", .data = &isl1208_configs[TYPE_ISL1208] },
+	{ .compatible = "isil,isl1209", .data = &isl1208_configs[TYPE_ISL1209] },
+	{ .compatible = "isil,isl1218", .data = &isl1208_configs[TYPE_ISL1218] },
+	{ .compatible = "isil,isl1219", .data = &isl1208_configs[TYPE_ISL1219] },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, isl1208_of_match);
+
+/* Device state */
+struct isl1208_state {
+	struct nvmem_config nvmem_config;
+	struct rtc_device *rtc;
+	const struct isl1208_config *config;
+};
+
+/* block read */
+static int
+isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
+		      unsigned len)
+{
+	int ret;
+
+	WARN_ON(reg > ISL1219_REG_YRT);
+	WARN_ON(reg + len > ISL1219_REG_YRT + 1);
+
+	ret = i2c_smbus_read_i2c_block_data(client, reg, len, buf);
+	return (ret < 0) ? ret : 0;
+}
+
+/* block write */
+static int
+isl1208_i2c_set_regs(struct i2c_client *client, u8 reg, u8 const buf[],
+		     unsigned len)
+{
+	int ret;
+
+	WARN_ON(reg > ISL1219_REG_YRT);
+	WARN_ON(reg + len > ISL1219_REG_YRT + 1);
+
+	ret = i2c_smbus_write_i2c_block_data(client, reg, len, buf);
+	return (ret < 0) ? ret : 0;
+}
+
+/* simple check to see whether we have a isl1208 */
+static int
+isl1208_i2c_validate_client(struct i2c_client *client)
+{
+	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
+	u8 zero_mask[ISL1208_RTC_SECTION_LEN] = {
+		0x80, 0x80, 0x40, 0xc0, 0xe0, 0x00, 0xf8
+	};
+	int i;
+	int ret;
+
+	ret = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < ISL1208_RTC_SECTION_LEN; ++i) {
+		if (regs[i] & zero_mask[i])	/* check if bits are cleared */
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int
+isl1208_i2c_get_sr(struct i2c_client *client)
+{
+	return i2c_smbus_read_byte_data(client, ISL1208_REG_SR);
+}
+
+static int
+isl1208_i2c_get_atr(struct i2c_client *client)
+{
+	int atr = i2c_smbus_read_byte_data(client, ISL1208_REG_ATR);
+	if (atr < 0)
+		return atr;
+
+	/* The 6bit value in the ATR register controls the load
+	 * capacitance C_load * in steps of 0.25pF
+	 *
+	 * bit (1<<5) of the ATR register is inverted
+	 *
+	 * C_load(ATR=0x20) =  4.50pF
+	 * C_load(ATR=0x00) = 12.50pF
+	 * C_load(ATR=0x1f) = 20.25pF
+	 *
+	 */
+
+	atr &= 0x3f;		/* mask out lsb */
+	atr ^= 1 << 5;		/* invert 6th bit */
+	atr += 2 * 9;		/* add offset of 4.5pF; unit[atr] = 0.25pF */
+
+	return atr;
+}
+
+/* returns adjustment value + 100 */
+static int
+isl1208_i2c_get_dtr(struct i2c_client *client)
+{
+	int dtr = i2c_smbus_read_byte_data(client, ISL1208_REG_DTR);
+	if (dtr < 0)
+		return -EIO;
+
+	/* dtr encodes adjustments of {-60,-40,-20,0,20,40,60} ppm */
+	dtr = ((dtr & 0x3) * 20) * (dtr & (1 << 2) ? -1 : 1);
+
+	return dtr + 100;
+}
+
+static int
+isl1208_i2c_get_usr(struct i2c_client *client)
+{
+	u8 buf[ISL1208_USR_SECTION_LEN] = { 0, };
+	int ret;
+
+	ret = isl1208_i2c_read_regs(client, ISL1208_REG_USR1, buf,
+				    ISL1208_USR_SECTION_LEN);
+	if (ret < 0)
+		return ret;
+
+	return (buf[1] << 8) | buf[0];
+}
+
+static int
+isl1208_i2c_set_usr(struct i2c_client *client, u16 usr)
+{
+	u8 buf[ISL1208_USR_SECTION_LEN];
+
+	buf[0] = usr & 0xff;
+	buf[1] = (usr >> 8) & 0xff;
+
+	return isl1208_i2c_set_regs(client, ISL1208_REG_USR1, buf,
+				    ISL1208_USR_SECTION_LEN);
+}
+
+static int
+isl1208_rtc_toggle_alarm(struct i2c_client *client, int enable)
+{
+	int icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
+
+	if (icr < 0) {
+		dev_err(&client->dev, "%s: reading INT failed\n", __func__);
+		return icr;
+	}
+
+	if (enable)
+		icr |= ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM;
+	else
+		icr &= ~(ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM);
+
+	icr = i2c_smbus_write_byte_data(client, ISL1208_REG_INT, icr);
+	if (icr < 0) {
+		dev_err(&client->dev, "%s: writing INT failed\n", __func__);
+		return icr;
+	}
+
+	return 0;
+}
+
+static int
+isl1208_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+	struct i2c_client *const client = to_i2c_client(dev);
+	int sr, dtr, atr, usr;
+
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
+		return sr;
+	}
+
+	seq_printf(seq, "status_reg\t:%s%s%s%s%s%s (0x%.2x)\n",
+		   (sr & ISL1208_REG_SR_RTCF) ? " RTCF" : "",
+		   (sr & ISL1208_REG_SR_BAT) ? " BAT" : "",
+		   (sr & ISL1208_REG_SR_ALM) ? " ALM" : "",
+		   (sr & ISL1208_REG_SR_WRTC) ? " WRTC" : "",
+		   (sr & ISL1208_REG_SR_XTOSCB) ? " XTOSCB" : "",
+		   (sr & ISL1208_REG_SR_ARST) ? " ARST" : "", sr);
+
+	seq_printf(seq, "batt_status\t: %s\n",
+		   (sr & ISL1208_REG_SR_RTCF) ? "bad" : "okay");
+
+	dtr = isl1208_i2c_get_dtr(client);
+	if (dtr >= 0)
+		seq_printf(seq, "digital_trim\t: %d ppm\n", dtr - 100);
+
+	atr = isl1208_i2c_get_atr(client);
+	if (atr >= 0)
+		seq_printf(seq, "analog_trim\t: %d.%.2d pF\n",
+			   atr >> 2, (atr & 0x3) * 25);
+
+	usr = isl1208_i2c_get_usr(client);
+	if (usr >= 0)
+		seq_printf(seq, "user_data\t: 0x%.4x\n", usr);
+
+	return 0;
+}
+
+static int
+isl1208_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
+{
+	int sr;
+	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
+
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
+		return -EIO;
+	}
+
+	sr = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading RTC section failed\n",
+			__func__);
+		return sr;
+	}
+
+	tm->tm_sec = bcd2bin(regs[ISL1208_REG_SC]);
+	tm->tm_min = bcd2bin(regs[ISL1208_REG_MN]);
+
+	/* HR field has a more complex interpretation */
+	{
+		const u8 _hr = regs[ISL1208_REG_HR];
+		if (_hr & ISL1208_REG_HR_MIL)	/* 24h format */
+			tm->tm_hour = bcd2bin(_hr & 0x3f);
+		else {
+			/* 12h format */
+			tm->tm_hour = bcd2bin(_hr & 0x1f);
+			if (_hr & ISL1208_REG_HR_PM)	/* PM flag set */
+				tm->tm_hour += 12;
+		}
+	}
+
+	tm->tm_mday = bcd2bin(regs[ISL1208_REG_DT]);
+	tm->tm_mon = bcd2bin(regs[ISL1208_REG_MO]) - 1;	/* rtc starts at 1 */
+	tm->tm_year = bcd2bin(regs[ISL1208_REG_YR]) + 100;
+	tm->tm_wday = bcd2bin(regs[ISL1208_REG_DW]);
+
+	return 0;
+}
+
+static int
+isl1208_i2c_read_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
+{
+	struct rtc_time *const tm = &alarm->time;
+	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
+	int icr, yr, sr = isl1208_i2c_get_sr(client);
+
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
+		return sr;
+	}
+
+	sr = isl1208_i2c_read_regs(client, ISL1208_REG_SCA, regs,
+				   ISL1208_ALARM_SECTION_LEN);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading alarm section failed\n",
+			__func__);
+		return sr;
+	}
+
+	/* MSB of each alarm register is an enable bit */
+	tm->tm_sec = bcd2bin(regs[ISL1208_REG_SCA - ISL1208_REG_SCA] & 0x7f);
+	tm->tm_min = bcd2bin(regs[ISL1208_REG_MNA - ISL1208_REG_SCA] & 0x7f);
+	tm->tm_hour = bcd2bin(regs[ISL1208_REG_HRA - ISL1208_REG_SCA] & 0x3f);
+	tm->tm_mday = bcd2bin(regs[ISL1208_REG_DTA - ISL1208_REG_SCA] & 0x3f);
+	tm->tm_mon =
+		bcd2bin(regs[ISL1208_REG_MOA - ISL1208_REG_SCA] & 0x1f) - 1;
+	tm->tm_wday = bcd2bin(regs[ISL1208_REG_DWA - ISL1208_REG_SCA] & 0x03);
+
+	/* The alarm doesn't store the year so get it from the rtc section */
+	yr = i2c_smbus_read_byte_data(client, ISL1208_REG_YR);
+	if (yr < 0) {
+		dev_err(&client->dev, "%s: reading RTC YR failed\n", __func__);
+		return yr;
+	}
+	tm->tm_year = bcd2bin(yr) + 100;
+
+	icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
+	if (icr < 0) {
+		dev_err(&client->dev, "%s: reading INT failed\n", __func__);
+		return icr;
+	}
+	alarm->enabled = !!(icr & ISL1208_REG_INT_ALME);
+
+	return 0;
+}
+
+static int
+isl1208_i2c_set_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
+{
+	struct rtc_time *alarm_tm = &alarm->time;
+	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
+	const int offs = ISL1208_REG_SCA;
+	struct rtc_time rtc_tm;
+	int err, enable;
+
+	err = isl1208_i2c_read_time(client, &rtc_tm);
+	if (err)
+		return err;
+
+	/* If the alarm time is before the current time disable the alarm */
+	if (!alarm->enabled || rtc_tm_sub(alarm_tm, &rtc_tm) <= 0)
+		enable = 0x00;
+	else
+		enable = 0x80;
+
+	/* Program the alarm and enable it for each setting */
+	regs[ISL1208_REG_SCA - offs] = bin2bcd(alarm_tm->tm_sec) | enable;
+	regs[ISL1208_REG_MNA - offs] = bin2bcd(alarm_tm->tm_min) | enable;
+	regs[ISL1208_REG_HRA - offs] = bin2bcd(alarm_tm->tm_hour) |
+		ISL1208_REG_HR_MIL | enable;
+
+	regs[ISL1208_REG_DTA - offs] = bin2bcd(alarm_tm->tm_mday) | enable;
+	regs[ISL1208_REG_MOA - offs] = bin2bcd(alarm_tm->tm_mon + 1) | enable;
+	regs[ISL1208_REG_DWA - offs] = bin2bcd(alarm_tm->tm_wday & 7) | enable;
+
+	/* write ALARM registers */
+	err = isl1208_i2c_set_regs(client, offs, regs,
+				  ISL1208_ALARM_SECTION_LEN);
+	if (err < 0) {
+		dev_err(&client->dev, "%s: writing ALARM section failed\n",
+			__func__);
+		return err;
+	}
+
+	err = isl1208_rtc_toggle_alarm(client, enable);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int
+isl1208_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	return isl1208_i2c_read_time(to_i2c_client(dev), tm);
+}
+
+static int
+isl1208_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
+{
+	int sr;
+	u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
+
+	/* The clock has an 8 bit wide bcd-coded register (they never learn)
+	 * for the year. tm_year is an offset from 1900 and we are interested
+	 * in the 2000-2099 range, so any value less than 100 is invalid.
+	 */
+	if (tm->tm_year < 100)
+		return -EINVAL;
+
+	regs[ISL1208_REG_SC] = bin2bcd(tm->tm_sec);
+	regs[ISL1208_REG_MN] = bin2bcd(tm->tm_min);
+	regs[ISL1208_REG_HR] = bin2bcd(tm->tm_hour) | ISL1208_REG_HR_MIL;
+
+	regs[ISL1208_REG_DT] = bin2bcd(tm->tm_mday);
+	regs[ISL1208_REG_MO] = bin2bcd(tm->tm_mon + 1);
+	regs[ISL1208_REG_YR] = bin2bcd(tm->tm_year - 100);
+
+	regs[ISL1208_REG_DW] = bin2bcd(tm->tm_wday & 7);
+
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
+		return sr;
+	}
+
+	/* set WRTC */
+	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
+				       sr | ISL1208_REG_SR_WRTC);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: writing SR failed\n", __func__);
+		return sr;
+	}
+
+	/* write RTC registers */
+	sr = isl1208_i2c_set_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: writing RTC section failed\n",
+			__func__);
+		return sr;
+	}
+
+	/* clear WRTC again */
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: reading SR failed\n", __func__);
+		return sr;
+	}
+	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
+				       sr & ~ISL1208_REG_SR_WRTC);
+	if (sr < 0) {
+		dev_err(&client->dev, "%s: writing SR failed\n", __func__);
+		return sr;
+	}
+
+	return 0;
+}
+
+
+static int
+isl1208_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	return isl1208_i2c_set_time(to_i2c_client(dev), tm);
+}
+
+static int
+isl1208_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	return isl1208_i2c_read_alarm(to_i2c_client(dev), alarm);
+}
+
+static int
+isl1208_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	return isl1208_i2c_set_alarm(to_i2c_client(dev), alarm);
+}
+
+static ssize_t timestamp0_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev->parent);
+	int sr;
+
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
+		dev_err(dev, "%s: reading SR failed\n", __func__);
+		return sr;
+	}
+
+	sr &= ~ISL1208_REG_SR_EVT;
+
+	sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
+	if (sr < 0)
+		dev_err(dev, "%s: writing SR failed\n",
+			__func__);
+
+	return count;
+};
+
+static ssize_t timestamp0_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev->parent);
+	u8 regs[ISL1219_EVT_SECTION_LEN] = { 0, };
+	struct rtc_time tm;
+	int sr;
+
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
+		dev_err(dev, "%s: reading SR failed\n", __func__);
+		return sr;
+	}
+
+	if (!(sr & ISL1208_REG_SR_EVT))
+		return 0;
+
+	sr = isl1208_i2c_read_regs(client, ISL1219_REG_SCT, regs,
+				   ISL1219_EVT_SECTION_LEN);
+	if (sr < 0) {
+		dev_err(dev, "%s: reading event section failed\n",
+			__func__);
+		return 0;
+	}
+
+	/* MSB of each alarm register is an enable bit */
+	tm.tm_sec = bcd2bin(regs[ISL1219_REG_SCT - ISL1219_REG_SCT] & 0x7f);
+	tm.tm_min = bcd2bin(regs[ISL1219_REG_MNT - ISL1219_REG_SCT] & 0x7f);
+	tm.tm_hour = bcd2bin(regs[ISL1219_REG_HRT - ISL1219_REG_SCT] & 0x3f);
+	tm.tm_mday = bcd2bin(regs[ISL1219_REG_DTT - ISL1219_REG_SCT] & 0x3f);
+	tm.tm_mon =
+		bcd2bin(regs[ISL1219_REG_MOT - ISL1219_REG_SCT] & 0x1f) - 1;
+	tm.tm_year = bcd2bin(regs[ISL1219_REG_YRT - ISL1219_REG_SCT]) + 100;
+
+	sr = rtc_valid_tm(&tm);
+	if (sr)
+		return sr;
+
+	return sprintf(buf, "%llu\n",
+				(unsigned long long)rtc_tm_to_time64(&tm));
+};
+
+static DEVICE_ATTR_RW(timestamp0);
+
+static irqreturn_t
+isl1208_rtc_interrupt(int irq, void *data)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+	struct i2c_client *client = data;
+	struct isl1208_state *isl1208 = i2c_get_clientdata(client);
+	int handled = 0, sr, err;
+
+	/*
+	 * I2C reads get NAK'ed if we read straight away after an interrupt?
+	 * Using a mdelay/msleep didn't seem to help either, so we work around
+	 * this by continually trying to read the register for a short time.
+	 */
+	while (1) {
+		sr = isl1208_i2c_get_sr(client);
+		if (sr >= 0)
+			break;
+
+		if (time_after(jiffies, timeout)) {
+			dev_err(&client->dev, "%s: reading SR failed\n",
+				__func__);
+			return sr;
+		}
+	}
+
+	if (sr & ISL1208_REG_SR_ALM) {
+		dev_dbg(&client->dev, "alarm!\n");
+
+		rtc_update_irq(isl1208->rtc, 1, RTC_IRQF | RTC_AF);
+
+		/* Clear the alarm */
+		sr &= ~ISL1208_REG_SR_ALM;
+		sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
+		if (sr < 0)
+			dev_err(&client->dev, "%s: writing SR failed\n",
+				__func__);
+		else
+			handled = 1;
+
+		/* Disable the alarm */
+		err = isl1208_rtc_toggle_alarm(client, 0);
+		if (err)
+			return err;
+	}
+
+	if (isl1208->config->has_tamper && (sr & ISL1208_REG_SR_EVT)) {
+		dev_warn(&client->dev, "event detected");
+		handled = 1;
+		if (isl1208->config->has_timestamp)
+			sysfs_notify(&isl1208->rtc->dev.kobj, NULL,
+				     dev_attr_timestamp0.attr.name);
+	}
+
+	return handled ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static const struct rtc_class_ops isl1208_rtc_ops = {
+	.proc = isl1208_rtc_proc,
+	.read_time = isl1208_rtc_read_time,
+	.set_time = isl1208_rtc_set_time,
+	.read_alarm = isl1208_rtc_read_alarm,
+	.set_alarm = isl1208_rtc_set_alarm,
+};
+
+/* sysfs interface */
+
+static ssize_t
+isl1208_sysfs_show_atrim(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	int atr = isl1208_i2c_get_atr(to_i2c_client(dev->parent));
+	if (atr < 0)
+		return atr;
+
+	return sprintf(buf, "%d.%.2d pF\n", atr >> 2, (atr & 0x3) * 25);
+}
+
+static DEVICE_ATTR(atrim, S_IRUGO, isl1208_sysfs_show_atrim, NULL);
+
+static ssize_t
+isl1208_sysfs_show_dtrim(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	int dtr = isl1208_i2c_get_dtr(to_i2c_client(dev->parent));
+	if (dtr < 0)
+		return dtr;
+
+	return sprintf(buf, "%d ppm\n", dtr - 100);
+}
+
+static DEVICE_ATTR(dtrim, S_IRUGO, isl1208_sysfs_show_dtrim, NULL);
+
+static ssize_t
+isl1208_sysfs_show_usr(struct device *dev,
+		       struct device_attribute *attr, char *buf)
+{
+	int usr = isl1208_i2c_get_usr(to_i2c_client(dev->parent));
+	if (usr < 0)
+		return usr;
+
+	return sprintf(buf, "0x%.4x\n", usr);
+}
+
+static ssize_t
+isl1208_sysfs_store_usr(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	int usr = -1;
+
+	if (buf[0] == '0' && (buf[1] == 'x' || buf[1] == 'X')) {
+		if (sscanf(buf, "%x", &usr) != 1)
+			return -EINVAL;
+	} else {
+		if (sscanf(buf, "%d", &usr) != 1)
+			return -EINVAL;
+	}
+
+	if (usr < 0 || usr > 0xffff)
+		return -EINVAL;
+
+	if (isl1208_i2c_set_usr(to_i2c_client(dev->parent), usr))
+		return -EIO;
+
+	return count;
+}
+
+static DEVICE_ATTR(usr, S_IRUGO | S_IWUSR, isl1208_sysfs_show_usr,
+		   isl1208_sysfs_store_usr);
+
+static struct attribute *isl1208_rtc_attrs[] = {
+	&dev_attr_atrim.attr,
+	&dev_attr_dtrim.attr,
+	&dev_attr_usr.attr,
+	NULL
+};
+
+static const struct attribute_group isl1208_rtc_sysfs_files = {
+	.attrs	= isl1208_rtc_attrs,
+};
+
+static struct attribute *isl1219_rtc_attrs[] = {
+	&dev_attr_timestamp0.attr,
+	NULL
+};
+
+static const struct attribute_group isl1219_rtc_sysfs_files = {
+	.attrs	= isl1219_rtc_attrs,
+};
+
+static int isl1208_nvmem_read(void *priv, unsigned int off, void *buf,
+			      size_t count)
+{
+	struct isl1208_state *isl1208 = priv;
+	struct i2c_client *client = to_i2c_client(isl1208->rtc->dev.parent);
+	int ret;
+
+	/* nvmem sanitizes offset/count for us, but count==0 is possible */
+	if (!count)
+		return count;
+	ret = isl1208_i2c_read_regs(client, ISL1208_REG_USR1 + off, buf,
+				    count);
+	return ret == 0 ? count : ret;
+}
+
+static int isl1208_nvmem_write(void *priv, unsigned int off, void *buf,
+			       size_t count)
+{
+	struct isl1208_state *isl1208 = priv;
+	struct i2c_client *client = to_i2c_client(isl1208->rtc->dev.parent);
+	int ret;
+
+	/* nvmem sanitizes off/count for us, but count==0 is possible */
+	if (!count)
+		return count;
+	ret = isl1208_i2c_set_regs(client, ISL1208_REG_USR1 + off, buf,
+				   count);
+
+	return ret == 0 ? count : ret;
+}
+
+static const struct nvmem_config isl1208_nvmem_config = {
+	.name = "isl1208_nvram",
+	.word_size = 1,
+	.stride = 1,
+	/* .size from chip specific config */
+	.reg_read = isl1208_nvmem_read,
+	.reg_write = isl1208_nvmem_write,
+};
+
+static int isl1208_setup_irq(struct i2c_client *client, int irq)
+{
+	int rc = devm_request_threaded_irq(&client->dev, irq, NULL,
+					isl1208_rtc_interrupt,
+					IRQF_SHARED | IRQF_ONESHOT,
+					isl1208_driver.driver.name,
+					client);
+	if (!rc) {
+		device_init_wakeup(&client->dev, 1);
+		enable_irq_wake(irq);
+	} else {
+		dev_err(&client->dev,
+			"Unable to request irq %d, no alarm support\n",
+			irq);
+	}
+	return rc;
+}
+
+static int
+isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+	int rc = 0;
+	struct isl1208_state *isl1208;
+	int evdet_irq = -1;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	if (isl1208_i2c_validate_client(client) < 0)
+		return -ENODEV;
+
+	/* Allocate driver state, point i2c client data to it */
+	isl1208 = devm_kzalloc(&client->dev, sizeof(*isl1208), GFP_KERNEL);
+	if (!isl1208)
+		return -ENOMEM;
+	i2c_set_clientdata(client, isl1208);
+
+	/* Determine which chip we have */
+	if (client->dev.of_node) {
+		isl1208->config = of_device_get_match_data(&client->dev);
+		if (!isl1208->config)
+			return -ENODEV;
+	} else {
+		if (id->driver_data >= ISL_LAST_ID)
+			return -ENODEV;
+		isl1208->config = &isl1208_configs[id->driver_data];
+	}
+
+	isl1208->rtc = devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(isl1208->rtc))
+		return PTR_ERR(isl1208->rtc);
+
+	isl1208->rtc->ops = &isl1208_rtc_ops;
+
+	/* Setup nvmem configuration in driver state struct */
+	isl1208->nvmem_config = isl1208_nvmem_config;
+	isl1208->nvmem_config.size = isl1208->config->nvmem_length;
+	isl1208->nvmem_config.priv = isl1208;
+
+	rc = isl1208_i2c_get_sr(client);
+	if (rc < 0) {
+		dev_err(&client->dev, "reading status failed\n");
+		return rc;
+	}
+
+	if (rc & ISL1208_REG_SR_RTCF)
+		dev_warn(&client->dev, "rtc power failure detected, "
+			 "please set clock.\n");
+
+	if (isl1208->config->has_tamper) {
+		struct device_node *np = client->dev.of_node;
+		u32 evienb;
+
+		rc = i2c_smbus_read_byte_data(client, ISL1219_REG_EV);
+		if (rc < 0) {
+			dev_err(&client->dev, "failed to read EV reg\n");
+			return rc;
+		}
+		rc |= ISL1219_REG_EV_EVEN;
+		if (!of_property_read_u32(np, "isil,ev-evienb", &evienb)) {
+			if (evienb)
+				rc |= ISL1219_REG_EV_EVIENB;
+			else
+				rc &= ~ISL1219_REG_EV_EVIENB;
+		}
+		rc = i2c_smbus_write_byte_data(client, ISL1219_REG_EV, rc);
+		if (rc < 0) {
+			dev_err(&client->dev, "could not enable tamper detection\n");
+			return rc;
+		}
+		evdet_irq = of_irq_get_byname(np, "evdet");
+	}
+	if (isl1208->config->has_timestamp) {
+		rc = rtc_add_group(isl1208->rtc, &isl1219_rtc_sysfs_files);
+		if (rc)
+			return rc;
+	}
+
+	rc = rtc_add_group(isl1208->rtc, &isl1208_rtc_sysfs_files);
+	if (rc)
+		return rc;
+
+	if (client->irq > 0)
+		rc = isl1208_setup_irq(client, client->irq);
+	if (rc)
+		return rc;
+
+	if (evdet_irq > 0 && evdet_irq != client->irq)
+		rc = isl1208_setup_irq(client, evdet_irq);
+	if (rc)
+		return rc;
+
+	rc = rtc_nvmem_register(isl1208->rtc, &isl1208->nvmem_config);
+	if (rc)
+		return rc;
+
+	return rtc_register_device(isl1208->rtc);
+}
+
+static struct i2c_driver isl1208_driver = {
+	.driver = {
+		.name = "rtc-isl1208",
+		.of_match_table = of_match_ptr(isl1208_of_match),
+	},
+	.probe = isl1208_probe,
+	.id_table = isl1208_id,
+};
+
+module_i2c_driver(isl1208_driver);
+
+MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
+MODULE_DESCRIPTION("Intersil ISL1208 RTC driver");
+MODULE_LICENSE("GPL");