[PATCH v4 07/11] rtc: isl1208: Add isl1208_set_xtoscb()

[Biju Das <biju.das.jz@bp.renesas.com>]

As per the HW manual, setting of XTOSCB bit as follws

If using an external clock signal, set the XTOSCB bit as 1 to
disable the crystal oscillator.

If using an external crystal, the XTOSCB bit needs to be set at 0
to enable the crystal oscillator.

Add isl1208_set_xtoscb() to set XTOSCB bit based on the clock-names
property. Fallback is enabling the internal crystal oscillator.

While at it, introduce a variable "sr" for reading status register
in probe() as it is reused for writing.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v4:
 * New patch.
---
 drivers/rtc/rtc-isl1208.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/rtc-isl1208.c b/drivers/rtc/rtc-isl1208.c
index 916e7d44c96f..5f91a3ca5920 100644
--- a/drivers/rtc/rtc-isl1208.c
+++ b/drivers/rtc/rtc-isl1208.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/bcd.h>
+#include <linux/clk.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
@@ -175,6 +176,16 @@ isl1208_i2c_validate_client(struct i2c_client *client)
 	return 0;
 }
 
+static int isl1208_set_xtoscb(struct i2c_client *client, int sr, bool int_osc_en)
+{
+	if (int_osc_en)
+		sr &= ~ISL1208_REG_SR_XTOSCB;
+	else
+		sr |= ISL1208_REG_SR_XTOSCB;
+
+	return i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
+}
+
 static int
 isl1208_i2c_get_sr(struct i2c_client *client)
 {
@@ -808,9 +819,13 @@ static int isl1208_setup_irq(struct i2c_client *client, int irq)
 static int
 isl1208_probe(struct i2c_client *client)
 {
-	int rc = 0;
 	struct isl1208_state *isl1208;
+	bool int_osc_en = true;
 	int evdet_irq = -1;
+	struct clk *clkin;
+	struct clk *xin;
+	int rc = 0;
+	int sr;
 
 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 		return -ENODEV;
@@ -837,6 +852,13 @@ isl1208_probe(struct i2c_client *client)
 		isl1208->config = (struct isl1208_config *)id->driver_data;
 	}
 
+	xin = devm_clk_get(&client->dev, "xin");
+	if (IS_ERR(xin)) {
+		clkin = devm_clk_get(&client->dev, "clkin");
+		if (!IS_ERR(clkin))
+			int_osc_en = false;
+	}
+
 	isl1208->rtc = devm_rtc_allocate_device(&client->dev);
 	if (IS_ERR(isl1208->rtc))
 		return PTR_ERR(isl1208->rtc);
@@ -848,13 +870,17 @@ isl1208_probe(struct i2c_client *client)
 	isl1208->nvmem_config.size = isl1208->config->nvmem_length;
 	isl1208->nvmem_config.priv = isl1208;
 
-	rc = isl1208_i2c_get_sr(client);
-	if (rc < 0) {
+	sr = isl1208_i2c_get_sr(client);
+	if (sr < 0) {
 		dev_err(&client->dev, "reading status failed\n");
-		return rc;
+		return sr;
 	}
 
-	if (rc & ISL1208_REG_SR_RTCF)
+	rc = isl1208_set_xtoscb(client, sr, int_osc_en);
+	if (rc)
+		return rc;
+
+	if (sr & ISL1208_REG_SR_RTCF)
 		dev_warn(&client->dev, "rtc power failure detected, "
 			 "please set clock.\n");
 
-- 
2.25.1