[PATCH v2 5/7] hwmon: sy7636a: read the temperature only while the rails are on

[Pablo Mazzini <pmazzini@gmail.com>]

The driver enables VCOM at probe, which keeps the panel's high voltage
rails on for good, and gets a dummy regulator if it probes before the
regulator exists. Read the temperature only while the rails are on, when
the chip samples it, and return -ENODATA otherwise. Read power good with
it in one transfer, so the value can not be from before the first sample
or after the rails went off. Register it under the chip name, as the
TPS65185 and FP9931 drivers do.

Signed-off-by: Pablo Mazzini <pmazzini@gmail.com>
---
 drivers/hwmon/sy7636a-hwmon.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/drivers/hwmon/sy7636a-hwmon.c b/drivers/hwmon/sy7636a-hwmon.c
index f01f368d68e5..475aff997c2d 100644
--- a/drivers/hwmon/sy7636a-hwmon.c
+++ b/drivers/hwmon/sy7636a-hwmon.c
@@ -14,7 +14,6 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
-#include <linux/regulator/machine.h>
 
 #include <linux/mfd/sy7636a.h>
 
@@ -22,14 +21,22 @@ static int sy7636a_read(struct device *dev, enum hwmon_sensor_types type,
 			u32 attr, int channel, long *temp)
 {
 	struct regmap *regmap = dev_get_drvdata(dev);
-	int ret, reg_val;
-
-	ret = regmap_read(regmap,
-			  SY7636A_REG_TERMISTOR_READOUT, &reg_val);
+	u8 buf[2];
+	int ret;
+
+	/*
+	 * Read power good and the thermistor in one transfer: the thermistor is
+	 * only sampled while the rails are on, and power good comes after the
+	 * first sample
+	 */
+	ret = regmap_bulk_read(regmap, SY7636A_REG_FAULT_FLAG, buf, sizeof(buf));
 	if (ret)
 		return ret;
 
-	*temp = (s8)reg_val * 1000;
+	if (!(buf[0] & SY7636A_FAULT_FLAG_PG))
+		return -ENODATA;
+
+	*temp = (s8)buf[1] * 1000;
 
 	return 0;
 }
@@ -72,12 +79,8 @@ static int sy7636a_sensor_probe(struct platform_device *pdev)
 	if (!regmap)
 		return -EPROBE_DEFER;
 
-	err = devm_regulator_get_enable(&pdev->dev, "vcom");
-	if (err)
-		return err;
-
 	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
-							 "sy7636a_temperature", regmap,
+							 "sy7636a", regmap,
 							 &sy7636a_chip_info, NULL);
 
 	if (IS_ERR(hwmon_dev)) {
-- 
2.52.0