[PATCH] hwmon:max6697: Allow max6581 to create tempX_offset attributes

[Chu Lin <linchuyuan@google.com>]

Per max6581, reg 4d and reg 4e is used for temperature read offset.
This patch will let the user specify the temperature read offset for
max6581. This patch is tested on max6581 and only applies to max6581.

Testing:
echo 16250 > temp2_offset
cat temp2_offset
16250

echo 17500 > temp3_offset
cat temp3_offset
17500
cat temp4_offset
0
cat temp2_offset
17500

echo 0 > temp2_offset
cat temp2_offset
0
cat temp3_offset
17500

echo -0 > temp2_offset
cat temp2_offset
0

echo -100000 > temp2_offset
-sh: echo: write error: Invalid argument

cat temp2_input
37000

echo 10000 > temp2_offset
cat temp2_input
47125

echo -2000 > temp2_offset
cat temp2_input
34875

echo -0 > temp2_offset
cat temp2_input
37000

Signed-off-by: Chu Lin <linchuyuan@google.com>
---
 drivers/hwmon/max6697.c | 129 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 125 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/max6697.c b/drivers/hwmon/max6697.c
index 743752a2467a..b11fcb594807 100644
--- a/drivers/hwmon/max6697.c
+++ b/drivers/hwmon/max6697.c
@@ -41,6 +41,14 @@ static const u8 MAX6697_REG_CRIT[] = {
 #define MAX6697_MAP_BITS(reg)	((((reg) & 0x7e) >> 1) | \
 				 (((reg) & 0x01) << 6) | ((reg) & 0x80))
 
+#define MAX6581_OFFSET_TO_MILLIC(reg)	(16000 * (((reg) & (1<<6)) >> 6) + \
+					 8000 * (((reg) & (1<<5)) >> 5) + \
+					 4000 * (((reg) & (1<<4)) >> 4) + \
+					 2000 * (((reg) & (1<<3)) >> 3) + \
+					 1000 * (((reg) & (1<<2)) >> 2) + \
+					 500 * (((reg) & (1<<1)) >> 1) + \
+					 250 * ((reg) & 1))
+
 #define MAX6697_REG_STAT(n)		(0x44 + (n))
 
 #define MAX6697_REG_CONFIG		0x41
@@ -56,6 +64,9 @@ static const u8 MAX6697_REG_CRIT[] = {
 #define MAX6581_REG_IDEALITY_SELECT	0x4c
 #define MAX6581_REG_OFFSET		0x4d
 #define MAX6581_REG_OFFSET_SELECT	0x4e
+#define MAX6581_OFFSET_MIN		-31750
+#define MAX6581_OFFSET_MAX		-MAX6581_OFFSET_MIN
+
 
 #define MAX6697_CONV_TIME		156	/* ms per channel, worst case */
 
@@ -316,6 +327,94 @@ static ssize_t temp_store(struct device *dev,
 	return ret < 0 ? ret : count;
 }
 
+static ssize_t offset_store(struct device *dev,
+			    struct device_attribute *devattr, const char *buf,
+			    size_t count)
+{
+	long temp;
+	u8 val, select;
+	int i, temp_frac, temp_int, ret, index;
+	bool sign;
+	struct max6697_data *data;
+
+	index = to_sensor_dev_attr(devattr)->index;
+	data = dev_get_drvdata(dev);
+	select = i2c_smbus_read_byte_data(data->client,
+					  MAX6581_REG_OFFSET_SELECT);
+	if (select < 0)
+		return -ENODATA;
+	ret = kstrtol(buf, 10, &temp);
+	if (ret < 0)
+		return ret;
+	if (temp > MAX6581_OFFSET_MAX || temp < MAX6581_OFFSET_MIN)
+		return -EINVAL;
+
+	/* disable the offset for channel */
+	if (temp == 0) {
+		ret = i2c_smbus_write_byte_data(data->client,
+						MAX6581_REG_OFFSET_SELECT,
+						select & ~(1<<(index-1)));
+		return ret < 0 ? ret : count;
+	}
+	sign = temp < 0 ? false : true;
+	temp = abs(temp);
+	temp_int = temp / 1000;
+	temp_frac = temp % 1000;
+	for (i = 4; i >= 0 && temp_int > 0; --i) {
+		if (temp_int >= 1<<i) {
+			temp_int -= 1<<i;
+			val |= 1 << (i+2);
+		}
+	}
+	/* special handle the fraction */
+	if (temp_frac % 250 != 0)
+		return -EINVAL;
+	if (temp_frac == 750)
+		val |= 0x3;
+	else if (temp_frac == 500)
+		val |= 0x2;
+	else if (temp_frac)
+		val |= 0x1;
+	ret = i2c_smbus_write_byte_data(data->client,
+					MAX6581_REG_OFFSET_SELECT,
+					select | 1<<(index-1));
+	if (ret < 0)
+		return ret;
+	ret = i2c_smbus_write_byte_data(data->client,
+					MAX6581_REG_OFFSET,
+					sign?val:(~val + 1));
+	return ret < 0 ? ret : count;
+}
+
+static ssize_t offset_show(struct device *dev, struct device_attribute *devattr,
+			   char *buf)
+{
+	int select, ret, index, temp;
+	struct max6697_data *data;
+
+	index = to_sensor_dev_attr(devattr)->index;
+	data = dev_get_drvdata(dev);
+	select = i2c_smbus_read_byte_data(data->client,
+				       MAX6581_REG_OFFSET_SELECT);
+	if (select < 0)
+		return -ENODATA;
+	if (select & (1<<(index-1))) {
+		ret = i2c_smbus_read_byte_data(data->client,
+					       MAX6581_REG_OFFSET);
+		if (ret < 0)
+			return -ENODATA;
+	} else {
+		return sprintf(buf, "%d\n", 0);
+	}
+	if (1<<7 & ret) {
+		ret = ~ret + 1;
+		temp = -MAX6581_OFFSET_TO_MILLIC(ret);
+	} else {
+		temp = MAX6581_OFFSET_TO_MILLIC(ret);
+	}
+	return sprintf(buf, "%d\n", temp);
+}
+
 static SENSOR_DEVICE_ATTR_RO(temp1_input, temp_input, 0);
 static SENSOR_DEVICE_ATTR_2_RW(temp1_max, temp, 0, MAX6697_TEMP_MAX);
 static SENSOR_DEVICE_ATTR_2_RW(temp1_crit, temp, 0, MAX6697_TEMP_CRIT);
@@ -374,6 +473,16 @@ static SENSOR_DEVICE_ATTR_RO(temp6_fault, alarm, 5);
 static SENSOR_DEVICE_ATTR_RO(temp7_fault, alarm, 6);
 static SENSOR_DEVICE_ATTR_RO(temp8_fault, alarm, 7);
 
+/* There is no offset for local temperature so starting from temp2 */
+static SENSOR_DEVICE_ATTR_RW(temp1_offset, offset, 0);
+static SENSOR_DEVICE_ATTR_RW(temp2_offset, offset, 1);
+static SENSOR_DEVICE_ATTR_RW(temp3_offset, offset, 2);
+static SENSOR_DEVICE_ATTR_RW(temp4_offset, offset, 3);
+static SENSOR_DEVICE_ATTR_RW(temp5_offset, offset, 4);
+static SENSOR_DEVICE_ATTR_RW(temp6_offset, offset, 5);
+static SENSOR_DEVICE_ATTR_RW(temp7_offset, offset, 6);
+static SENSOR_DEVICE_ATTR_RW(temp8_offset, offset, 7);
+
 static DEVICE_ATTR(dummy, 0, NULL, NULL);
 
 static umode_t max6697_is_visible(struct kobject *kobj, struct attribute *attr,
@@ -382,8 +491,8 @@ static umode_t max6697_is_visible(struct kobject *kobj, struct attribute *attr,
 	struct device *dev = container_of(kobj, struct device, kobj);
 	struct max6697_data *data = dev_get_drvdata(dev);
 	const struct max6697_chip_data *chip = data->chip;
-	int channel = index / 6;	/* channel number */
-	int nr = index % 6;		/* attribute index within channel */
+	int channel = index / 8;	/* channel number */
+	int nr = index % 7;		/* attribute index within channel */
 
 	if (channel >= chip->channels)
 		return 0;
@@ -392,6 +501,10 @@ static umode_t max6697_is_visible(struct kobject *kobj, struct attribute *attr,
 		return 0;
 	if (nr == 5 && !(chip->have_fault & (1 << channel)))
 		return 0;
+	/* offset reg is only supported on max6581 remote channels */
+	if (nr == 6)
+		if (data->type != max6581 || channel == 0)
+			return 0;
 
 	return attr->mode;
 }
@@ -408,6 +521,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp1_crit.dev_attr.attr,
 	&sensor_dev_attr_temp1_crit_alarm.dev_attr.attr,
 	&dev_attr_dummy.attr,
+	&sensor_dev_attr_temp1_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp2_input.dev_attr.attr,
 	&sensor_dev_attr_temp2_max.dev_attr.attr,
@@ -415,6 +529,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp2_crit.dev_attr.attr,
 	&sensor_dev_attr_temp2_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp2_fault.dev_attr.attr,
+	&sensor_dev_attr_temp2_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp3_input.dev_attr.attr,
 	&sensor_dev_attr_temp3_max.dev_attr.attr,
@@ -422,6 +537,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp3_crit.dev_attr.attr,
 	&sensor_dev_attr_temp3_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp3_fault.dev_attr.attr,
+	&sensor_dev_attr_temp3_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp4_input.dev_attr.attr,
 	&sensor_dev_attr_temp4_max.dev_attr.attr,
@@ -429,6 +545,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp4_crit.dev_attr.attr,
 	&sensor_dev_attr_temp4_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp4_fault.dev_attr.attr,
+	&sensor_dev_attr_temp4_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp5_input.dev_attr.attr,
 	&sensor_dev_attr_temp5_max.dev_attr.attr,
@@ -436,6 +553,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp5_crit.dev_attr.attr,
 	&sensor_dev_attr_temp5_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp5_fault.dev_attr.attr,
+	&sensor_dev_attr_temp5_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp6_input.dev_attr.attr,
 	&sensor_dev_attr_temp6_max.dev_attr.attr,
@@ -443,6 +561,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp6_crit.dev_attr.attr,
 	&sensor_dev_attr_temp6_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp6_fault.dev_attr.attr,
+	&sensor_dev_attr_temp6_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp7_input.dev_attr.attr,
 	&sensor_dev_attr_temp7_max.dev_attr.attr,
@@ -450,6 +569,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp7_crit.dev_attr.attr,
 	&sensor_dev_attr_temp7_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp7_fault.dev_attr.attr,
+	&sensor_dev_attr_temp7_offset.dev_attr.attr,
 
 	&sensor_dev_attr_temp8_input.dev_attr.attr,
 	&sensor_dev_attr_temp8_max.dev_attr.attr,
@@ -457,6 +577,7 @@ static struct attribute *max6697_attributes[] = {
 	&sensor_dev_attr_temp8_crit.dev_attr.attr,
 	&sensor_dev_attr_temp8_crit_alarm.dev_attr.attr,
 	&sensor_dev_attr_temp8_fault.dev_attr.attr,
+	&sensor_dev_attr_temp8_offset.dev_attr.attr,
 	NULL
 };
 
@@ -493,8 +614,8 @@ static void max6697_get_config_of(struct device_node *node,
 	}
 	prop = of_get_property(node, "transistor-ideality", &len);
 	if (prop && len == 2 * sizeof(u32)) {
-			pdata->ideality_mask = be32_to_cpu(prop[0]);
-			pdata->ideality_value = be32_to_cpu(prop[1]);
+		pdata->ideality_mask = be32_to_cpu(prop[0]);
+		pdata->ideality_value = be32_to_cpu(prop[1]);
 	}
 }
 
-- 
2.27.0.212.ge8ba1cc988-goog