[PATCH RFC 5/6] rtc: isl1208: Add support for the built-in RTC on the PMIC RAA215300

[Biju Das <biju.das.jz@xxxxxxxxxxxxxx>]

The built-in RTC found on PMIC RAA215300 is the same as ISL1208.
However, the external oscillator polarity is determined by the
PMIC version. For eg: the PMIC version has inverted polarity for
the external oscillator and the corresponding bit in RTC need to
be inverted(XTOSCB). This info needs to be shared from PMIC driver
to RTC driver, so that it can support all versions without any code
changes.

Add a new compatible renesas,raa215300-isl1208 to support RTC found
on PMIC RAA215300 and renesas,raa215300-pmic property to support
different versions.

Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
 drivers/rtc/rtc-isl1208.c | 50 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/rtc/rtc-isl1208.c b/drivers/rtc/rtc-isl1208.c
index 73cc6aaf9b8b..f4ea19691ac1 100644
--- a/drivers/rtc/rtc-isl1208.c
+++ b/drivers/rtc/rtc-isl1208.c
@@ -74,6 +74,7 @@ enum isl1208_id {
 	TYPE_ISL1209,
 	TYPE_ISL1218,
 	TYPE_ISL1219,
+	TYPE_RAA215300_ISL1208,
 	ISL_LAST_ID
 };
 
@@ -83,11 +84,13 @@ static const struct isl1208_config {
 	unsigned int	nvmem_length;
 	unsigned	has_tamper:1;
 	unsigned	has_timestamp:1;
+	unsigned	has_pmic_parent: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 },
+	[TYPE_RAA215300_ISL1208] = { "isl1208", 2, false, false, true },
 };
 
 static const struct i2c_device_id isl1208_id[] = {
@@ -104,6 +107,10 @@ static const __maybe_unused struct of_device_id isl1208_of_match[] = {
 	{ .compatible = "isil,isl1209", .data = &isl1208_configs[TYPE_ISL1209] },
 	{ .compatible = "isil,isl1218", .data = &isl1208_configs[TYPE_ISL1218] },
 	{ .compatible = "isil,isl1219", .data = &isl1208_configs[TYPE_ISL1219] },
+	{
+		.compatible = "renesas,raa215300-isl1208",
+		.data = &isl1208_configs[TYPE_RAA215300_ISL1208]
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, isl1208_of_match);
@@ -166,6 +173,43 @@ isl1208_i2c_validate_client(struct i2c_client *client)
 	return 0;
 }
 
+static bool isl1208_is_xtosc_polarity_inverted(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct i2c_client *pmic_dev;
+	unsigned int *pmic_version;
+	struct device_node *np;
+	bool ret = false;
+
+	np = of_parse_phandle(dev->of_node, "renesas,raa215300-pmic", 0);
+	if (np)
+		pmic_dev = of_find_i2c_device_by_node(np);
+
+	of_node_put(np);
+	if (!pmic_dev)
+		return ret;
+
+	pmic_version = dev_get_drvdata(&pmic_dev->dev);
+	/* External Oscillator polarity is inverted on revision 0x12 onwards */
+	if (*pmic_version >= 0x12)
+		ret = true;
+
+	put_device(&pmic_dev->dev);
+
+	return ret;
+}
+
+static int
+isl1208_set_ext_osc_based_on_pmic_version(struct i2c_client *client, int rc)
+{
+	if (isl1208_is_xtosc_polarity_inverted(client))
+		rc &= ~ISL1208_REG_SR_XTOSCB;
+	else
+		rc |= ISL1208_REG_SR_XTOSCB;
+
+	return i2c_smbus_write_byte_data(client, ISL1208_REG_SR, rc);
+}
+
 static int
 isl1208_i2c_get_sr(struct i2c_client *client)
 {
@@ -845,6 +889,12 @@ isl1208_probe(struct i2c_client *client)
 		return rc;
 	}
 
+	if (isl1208->config->has_pmic_parent) {
+		rc = isl1208_set_ext_osc_based_on_pmic_version(client, rc);
+		if (rc)
+			return rc;
+	}
+
 	if (rc & ISL1208_REG_SR_RTCF)
 		dev_warn(&client->dev, "rtc power failure detected, "
 			 "please set clock.\n");
-- 
2.25.1