rtc: isl1208: add support for isl1219 with tamper detection

We add support for the ISL1219 chip that got an integrated tamper
detection function. This patch implements the feature by adding
an additional timestamp0 file to sysfs device path.
This file contains seconds since epoch, if an event occurred,
or is empty, if none occurred.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Denis Osterland <Denis.Osterland@diehl.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-isl1208.c

@@ -14,6 +14,7 @@
 #include <linux/i2c.h>
 #include <linux/bcd.h>
 #include <linux/rtc.h>
+#include "rtc-core.h"
 
 /* Register map */
 /* rtc section */
@@ -33,13 +34,15 @@
 #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 ISL1208_REG_09  0x09	/* reserved */
+#define ISL1219_REG_EV  0x09
+#define ISL1219_REG_EV_EVEN    (1<<4)   /* event detection enable */
 #define ISL1208_REG_ATR 0x0a
 #define ISL1208_REG_DTR 0x0b
 
@@ -57,8 +60,24 @@
 #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 {
+	TYPE_ISL1208 = 0,
+	TYPE_ISL1218,
+	TYPE_ISL1219,
+};
+
 /* block read */
 static int
 isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
@@ -80,8 +99,8 @@ isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
 	};
 	int ret;
 
-	BUG_ON(reg > ISL1208_REG_USR2);
-	BUG_ON(reg + len > ISL1208_REG_USR2 + 1);
+	WARN_ON(reg > ISL1219_REG_YRT);
+	WARN_ON(reg + len > ISL1219_REG_YRT + 1);
 
 	ret = i2c_transfer(client->adapter, msgs, 2);
 	if (ret > 0)
@@ -104,8 +123,8 @@ isl1208_i2c_set_regs(struct i2c_client *client, u8 reg, u8 const buf[],
 	};
 	int ret;
 
-	BUG_ON(reg > ISL1208_REG_USR2);
-	BUG_ON(reg + len > ISL1208_REG_USR2 + 1);
+	WARN_ON(reg > ISL1219_REG_YRT);
+	WARN_ON(reg + len > ISL1219_REG_YRT + 1);
 
 	i2c_buf[0] = reg;
 	memcpy(&i2c_buf[1], &buf[0], len);
@@ -493,6 +512,73 @@ 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 = dev_get_drvdata(dev);
+	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 = dev_get_drvdata(dev);
+	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)
 {
@@ -538,6 +624,13 @@ isl1208_rtc_interrupt(int irq, void *data)
 			return err;
 	}
 
+	if (sr & ISL1208_REG_SR_EVT) {
+		sysfs_notify(&rtc->dev.kobj, NULL,
+			     dev_attr_timestamp0.attr.name);
+		dev_warn(&client->dev, "event detected");
+		handled = 1;
+	}
+
 	return handled ? IRQ_HANDLED : IRQ_NONE;
 }
 
@@ -623,6 +716,15 @@ 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_probe(struct i2c_client *client, const struct i2c_device_id *id)
 {
@@ -642,6 +744,7 @@ isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	rtc->ops = &isl1208_rtc_ops;
 
 	i2c_set_clientdata(client, rtc);
+	dev_set_drvdata(&rtc->dev, client);
 
 	rc = isl1208_i2c_get_sr(client);
 	if (rc < 0) {
@@ -653,6 +756,18 @@ isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		dev_warn(&client->dev, "rtc power failure detected, "
 			 "please set clock.\n");
 
+	if (id->driver_data == TYPE_ISL1219) {
+		rc = i2c_smbus_write_byte_data(client, ISL1219_REG_EV,
+					       ISL1219_REG_EV_EVEN);
+		if (rc < 0) {
+			dev_err(&client->dev, "could not enable tamper detection\n");
+			return rc;
+		}
+		rc = rtc_add_group(rtc, &isl1219_rtc_sysfs_files);
+		if (rc)
+			return rc;
+	}
+
 	rc = sysfs_create_group(&client->dev.kobj, &isl1208_rtc_sysfs_files);
 	if (rc)
 		return rc;
@@ -686,8 +801,9 @@ isl1208_remove(struct i2c_client *client)
 }
 
 static const struct i2c_device_id isl1208_id[] = {
-	{ "isl1208", 0 },
-	{ "isl1218", 0 },
+	{ "isl1208", TYPE_ISL1208 },
+	{ "isl1218", TYPE_ISL1218 },
+	{ "isl1219", TYPE_ISL1219 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, isl1208_id);
@@ -695,6 +811,7 @@ MODULE_DEVICE_TABLE(i2c, isl1208_id);
 static const struct of_device_id isl1208_of_match[] = {
 	{ .compatible = "isil,isl1208" },
 	{ .compatible = "isil,isl1218" },
+	{ .compatible = "isil,isl1219" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, isl1208_of_match);