drivers/rtc/rtc-isl12057.c: add alarm support to Intersil ISL12057 RTC driver

This patch adds alarm support to Intersil ISL12057 driver.  This allows to
configure the chip to generate an interrupt when the alarm matches current
time value.  Alarm can be programmed up to one month in the future and is
accurate to the second.

The patch was developed to support two different configurations: systems
w/ and w/o RTC chip IRQ line connected to the main CPU.

The latter is the one found on current 3 kernel users of the chip for
which support was initially developed (Netgear ReadyNAS 102, 104 and 2120
NAS).  On those devices, the IRQ#2 pin of the chip is not connected to the
SoC but to a PMIC.  This allows setting an alarm, powering off the device
and have it wake up when the alarm rings.  To support that configuration
the driver does the following:

 1. it has alarm_irq_enable() function returns -ENOTTY when no IRQ
    is passed to the driver.
 2. it marks the device as a wakeup source in all cases (whether an
    IRQ is passed to the driver or not) to have 'wakealarm' sysfs
    entry created.
 3. it marks the device has not supporting UIE mode when no IRQ is
    passed to the driver (see the commmit message of c9f5c7e7)

This specific configuration was tested on a ReadyNAS 102 by setting an
alarm, powering off the device and see it reboot as expected when the
alarm rang.

The former configuration was tested on a Netgear ReadyNAS 102 after some
soldering of the IRQ#2 pin of the RTC chip to a MPP line of the SoC (the
one used usually handles the reset button).  The test was performed using
a modified .dts file reflecting this change (see below) and rtc-test.c
program available in Documentation/rtc.txt.  This test program ran as
expected, which validates alarm supports, including interrupt support.

As a side note, the ISL12057 remains in the list of trivial devices, i.e.
no specific DT binding being added by this patch: i2c core automatically
handles extraction of IRQ line info from .dts file.  For instance, if one
wants to reference the interrupt line for the alarm in its .dts file,
adding interrupt and interrupt-parent properties works as expected:

          isl12057: isl12057@68 {
                  compatible =3D "isil,isl12057";
                  interrupt-parent =3D <&gpio0>;
                  interrupts =3D <6 IRQ_TYPE_EDGE_FALLING>;
                  reg =3D <0x68>;
          };

FWIW, if someone is looking for a way to test alarm support on a system on
which the chip IRQ line has the ability to boot the system (e.g.  ReadyNAS
102, 104, etc):

    # echo 0 > /sys/class/rtc/rtc0/wakealarm
    # echo `date '+%s' -d '+ 1 minutes'` > /sys/class/rtc/rtc0/wakealarm
    # shutdown -h now

With the commands above, after a minute, the system comes back to life.
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Peter Huewe <peter.huewe@infineon.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Uwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-isl12057.c

@@ -79,8 +79,10 @@
 #define ISL12057_MEM_MAP_LEN	0x10
 
 struct isl12057_rtc_data {
+	struct rtc_device *rtc;
 	struct regmap *regmap;
 	struct mutex lock;
+	int irq;
 };
 
 static void isl12057_rtc_regs_to_tm(struct rtc_time *tm, u8 *regs)
@@ -160,14 +162,47 @@ static int isl12057_i2c_validate_chip(struct regmap *regmap)
 	return 0;
 }
 
-static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
+static int _isl12057_rtc_clear_alarm(struct device *dev)
+{
+	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = regmap_update_bits(data->regmap, ISL12057_REG_SR,
+				 ISL12057_REG_SR_A1F, 0);
+	if (ret)
+		dev_err(dev, "%s: clearing alarm failed (%d)\n", __func__, ret);
+
+	return ret;
+}
+
+static int _isl12057_rtc_update_alarm(struct device *dev, int enable)
+{
+	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = regmap_update_bits(data->regmap, ISL12057_REG_INT,
+				 ISL12057_REG_INT_A1IE,
+				 enable ? ISL12057_REG_INT_A1IE : 0);
+	if (ret)
+		dev_err(dev, "%s: changing alarm interrupt flag failed (%d)\n",
+			__func__, ret);
+
+	return ret;
+}
+
+/*
+ * Note: as we only read from device and do not perform any update, there is
+ * no need for an equivalent function which would try and get driver's main
+ * lock. Here, it is safe for everyone if we just use regmap internal lock
+ * on the device when reading.
+ */
+static int _isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
 	u8 regs[ISL12057_RTC_SEC_LEN];
 	unsigned int sr;
 	int ret;
 
-	mutex_lock(&data->lock);
 	ret = regmap_read(data->regmap, ISL12057_REG_SR, &sr);
 	if (ret) {
 		dev_err(dev, "%s: unable to read oscillator status flag (%d)\n",
@@ -187,8 +222,6 @@ static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
 			__func__, ret);
 
 out:
-	mutex_unlock(&data->lock);
-
 	if (ret)
 		return ret;
 
@@ -197,6 +230,168 @@ static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	return rtc_valid_tm(tm);
 }
 
+static int isl12057_rtc_update_alarm(struct device *dev, int enable)
+{
+	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	mutex_lock(&data->lock);
+	ret = _isl12057_rtc_update_alarm(dev, enable);
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int isl12057_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+	struct rtc_time rtc_tm, *alarm_tm = &alarm->time;
+	unsigned long rtc_secs, alarm_secs;
+	u8 regs[ISL12057_A1_SEC_LEN];
+	unsigned int ir;
+	int ret;
+
+	mutex_lock(&data->lock);
+	ret = regmap_bulk_read(data->regmap, ISL12057_REG_A1_SC, regs,
+			       ISL12057_A1_SEC_LEN);
+	if (ret) {
+		dev_err(dev, "%s: reading alarm section failed (%d)\n",
+			__func__, ret);
+		goto err_unlock;
+	}
+
+	alarm_tm->tm_sec  = bcd2bin(regs[0] & 0x7f);
+	alarm_tm->tm_min  = bcd2bin(regs[1] & 0x7f);
+	alarm_tm->tm_hour = bcd2bin(regs[2] & 0x3f);
+	alarm_tm->tm_mday = bcd2bin(regs[3] & 0x3f);
+	alarm_tm->tm_wday = -1;
+
+	/*
+	 * The alarm section does not store year/month. We use the ones in rtc
+	 * section as a basis and increment month and then year if needed to get
+	 * alarm after current time.
+	 */
+	ret = _isl12057_rtc_read_time(dev, &rtc_tm);
+	if (ret)
+		goto err_unlock;
+
+	alarm_tm->tm_year = rtc_tm.tm_year;
+	alarm_tm->tm_mon = rtc_tm.tm_mon;
+
+	ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
+	if (ret)
+		goto err_unlock;
+
+	ret = rtc_tm_to_time(alarm_tm, &alarm_secs);
+	if (ret)
+		goto err_unlock;
+
+	if (alarm_secs < rtc_secs) {
+		if (alarm_tm->tm_mon == 11) {
+			alarm_tm->tm_mon = 0;
+			alarm_tm->tm_year += 1;
+		} else {
+			alarm_tm->tm_mon += 1;
+		}
+	}
+
+	ret = regmap_read(data->regmap, ISL12057_REG_INT, &ir);
+	if (ret) {
+		dev_err(dev, "%s: reading alarm interrupt flag failed (%d)\n",
+			__func__, ret);
+		goto err_unlock;
+	}
+
+	alarm->enabled = !!(ir & ISL12057_REG_INT_A1IE);
+
+err_unlock:
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int isl12057_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+	struct rtc_time *alarm_tm = &alarm->time;
+	unsigned long rtc_secs, alarm_secs;
+	u8 regs[ISL12057_A1_SEC_LEN];
+	struct rtc_time rtc_tm;
+	int ret, enable = 1;
+
+	mutex_lock(&data->lock);
+	ret = _isl12057_rtc_read_time(dev, &rtc_tm);
+	if (ret)
+		goto err_unlock;
+
+	ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
+	if (ret)
+		goto err_unlock;
+
+	ret = rtc_tm_to_time(alarm_tm, &alarm_secs);
+	if (ret)
+		goto err_unlock;
+
+	/* If alarm time is before current time, disable the alarm */
+	if (!alarm->enabled || alarm_secs <= rtc_secs) {
+		enable = 0;
+	} else {
+		/*
+		 * Chip only support alarms up to one month in the future. Let's
+		 * return an error if we get something after that limit.
+		 * Comparison is done by incrementing rtc_tm month field by one
+		 * and checking alarm value is still below.
+		 */
+		if (rtc_tm.tm_mon == 11) { /* handle year wrapping */
+			rtc_tm.tm_mon = 0;
+			rtc_tm.tm_year += 1;
+		} else {
+			rtc_tm.tm_mon += 1;
+		}
+
+		ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
+		if (ret)
+			goto err_unlock;
+
+		if (alarm_secs > rtc_secs) {
+			dev_err(dev, "%s: max for alarm is one month (%d)\n",
+				__func__, ret);
+			ret = -EINVAL;
+			goto err_unlock;
+		}
+	}
+
+	/* Disable the alarm before modifying it */
+	ret = _isl12057_rtc_update_alarm(dev, 0);
+	if (ret < 0) {
+		dev_err(dev, "%s: unable to disable the alarm (%d)\n",
+			__func__, ret);
+		goto err_unlock;
+	}
+
+	/* Program alarm registers */
+	regs[0] = bin2bcd(alarm_tm->tm_sec) & 0x7f;
+	regs[1] = bin2bcd(alarm_tm->tm_min) & 0x7f;
+	regs[2] = bin2bcd(alarm_tm->tm_hour) & 0x3f;
+	regs[3] = bin2bcd(alarm_tm->tm_mday) & 0x3f;
+
+	ret = regmap_bulk_write(data->regmap, ISL12057_REG_A1_SC, regs,
+				ISL12057_A1_SEC_LEN);
+	if (ret < 0) {
+		dev_err(dev, "%s: writing alarm section failed (%d)\n",
+			__func__, ret);
+		goto err_unlock;
+	}
+
+	/* Enable or disable alarm */
+	ret = _isl12057_rtc_update_alarm(dev, enable);
+
+err_unlock:
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
 static int isl12057_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
@@ -262,9 +457,48 @@ static int isl12057_check_rtc_status(struct device *dev, struct regmap *regmap)
 	return 0;
 }
 
+static int isl12057_rtc_alarm_irq_enable(struct device *dev,
+					 unsigned int enable)
+{
+	struct isl12057_rtc_data *rtc_data = dev_get_drvdata(dev);
+	int ret = -ENOTTY;
+
+	if (rtc_data->irq)
+		ret = isl12057_rtc_update_alarm(dev, enable);
+
+	return ret;
+}
+
+static irqreturn_t isl12057_rtc_interrupt(int irq, void *data)
+{
+	struct i2c_client *client = data;
+	struct isl12057_rtc_data *rtc_data = dev_get_drvdata(&client->dev);
+	struct rtc_device *rtc = rtc_data->rtc;
+	int ret, handled = IRQ_NONE;
+	unsigned int sr;
+
+	ret = regmap_read(rtc_data->regmap, ISL12057_REG_SR, &sr);
+	if (!ret && (sr & ISL12057_REG_SR_A1F)) {
+		dev_dbg(&client->dev, "RTC alarm!\n");
+
+		rtc_update_irq(rtc, 1, RTC_IRQF | RTC_AF);
+
+		/* Acknowledge and disable the alarm */
+		_isl12057_rtc_clear_alarm(&client->dev);
+		_isl12057_rtc_update_alarm(&client->dev, 0);
+
+		handled = IRQ_HANDLED;
+	}
+
+	return handled;
+}
+
 static const struct rtc_class_ops rtc_ops = {
-	.read_time = isl12057_rtc_read_time,
+	.read_time = _isl12057_rtc_read_time,
 	.set_time = isl12057_rtc_set_time,
+	.read_alarm = isl12057_rtc_read_alarm,
+	.set_alarm = isl12057_rtc_set_alarm,
+	.alarm_irq_enable = isl12057_rtc_alarm_irq_enable,
 };
 
 static struct regmap_config isl12057_rtc_regmap_config = {
@@ -277,7 +511,6 @@ static int isl12057_probe(struct i2c_client *client,
 {
 	struct device *dev = &client->dev;
 	struct isl12057_rtc_data *data;
-	struct rtc_device *rtc;
 	struct regmap *regmap;
 	int ret;
 
@@ -310,10 +543,72 @@ static int isl12057_probe(struct i2c_client *client,
 	data->regmap = regmap;
 	dev_set_drvdata(dev, data);
 
-	rtc = devm_rtc_device_register(dev, DRV_NAME, &rtc_ops, THIS_MODULE);
-	return PTR_ERR_OR_ZERO(rtc);
+	if (client->irq > 0) {
+		ret = devm_request_threaded_irq(dev, client->irq, NULL,
+						isl12057_rtc_interrupt,
+						IRQF_SHARED|IRQF_ONESHOT,
+						DRV_NAME, client);
+		if (!ret)
+			data->irq = client->irq;
+		else
+			dev_err(dev, "%s: irq %d unavailable (%d)\n", __func__,
+				client->irq, ret);
+	}
+
+	device_init_wakeup(dev, !!data->irq);
+
+	data->rtc = devm_rtc_device_register(dev, DRV_NAME, &rtc_ops,
+					     THIS_MODULE);
+	ret = PTR_ERR_OR_ZERO(data->rtc);
+	if (ret) {
+		dev_err(dev, "%s: unable to register RTC device (%d)\n",
+			__func__, ret);
+		goto err;
+	}
+
+	/* We cannot support UIE mode if we do not have an IRQ line */
+	if (!data->irq)
+		data->rtc->uie_unsupported = 1;
+
+err:
+	return ret;
+}
+
+static int isl12057_remove(struct i2c_client *client)
+{
+	struct isl12057_rtc_data *rtc_data = dev_get_drvdata(&client->dev);
+
+	if (rtc_data->irq)
+		device_init_wakeup(&client->dev, false);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int isl12057_rtc_suspend(struct device *dev)
+{
+	struct isl12057_rtc_data *rtc_data = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		return enable_irq_wake(rtc_data->irq);
+
+	return 0;
 }
 
+static int isl12057_rtc_resume(struct device *dev)
+{
+	struct isl12057_rtc_data *rtc_data = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		return disable_irq_wake(rtc_data->irq);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(isl12057_rtc_pm_ops, isl12057_rtc_suspend,
+			 isl12057_rtc_resume);
+
 #ifdef CONFIG_OF
 static const struct of_device_id isl12057_dt_match[] = {
 	{ .compatible = "isl,isl12057" },
@@ -331,9 +626,11 @@ static struct i2c_driver isl12057_driver = {
 	.driver = {
 		.name = DRV_NAME,
 		.owner = THIS_MODULE,
+		.pm = &isl12057_rtc_pm_ops,
 		.of_match_table = of_match_ptr(isl12057_dt_match),
 	},
 	.probe	  = isl12057_probe,
+	.remove	  = isl12057_remove,
 	.id_table = isl12057_id,
 };
 module_i2c_driver(isl12057_driver);