linux-kernel - [PATCH v5 1/2] hwmon: (adt7475) Added attenuator bypass support

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Date:   Fri, 24 Jan 2020 11:05:32 +1300
From:   Logan Shaw <logan.shaw@...iedtelesis.co.nz>
To:     linux@...ck-us.net, jdelvare@...e.com, robh+dt@...nel.org
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Joshua.Scott@...iedtelesis.co.nz,
        Chris.Packham@...iedtelesis.co.nz, logan.shaw@...iedtelesis.co.nz
Subject: [PATCH v5 1/2] hwmon: (adt7475) Added attenuator bypass support

Added support for reading DTS properties to set attenuators on
device probe for the ADT7473, ADT7475, ADT7476, and ADT7490.

Signed-off-by: Logan Shaw <logan.shaw@...iedtelesis.co.nz>
---
---
 drivers/hwmon/adt7475.c | 68 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/drivers/hwmon/adt7475.c b/drivers/hwmon/adt7475.c
index 6c64d50c9aae..8afc5a89ec92 100644
--- a/drivers/hwmon/adt7475.c
+++ b/drivers/hwmon/adt7475.c
@@ -19,6 +19,7 @@
 #include <linux/hwmon-vid.h>
 #include <linux/err.h>
 #include <linux/jiffies.h>
+#include <linux/of.h>
 #include <linux/util_macros.h>
 
 /* Indexes for the sysfs hooks */
@@ -1457,6 +1458,70 @@ static int adt7475_update_limits(struct i2c_client *client)
 	return 0;
 }
 
+/**
+ * Sets or clears the given bit in the config depending on the value of the
+ * given dts property. Non-zero value sets, zero value clears. No change if
+ * the property is absent.
+ */
+static void modify_config(const struct i2c_client *client, char *property,
+				u8 *config, u8 bit_index)
+{
+	u32 prop_value = 0;
+	int ret = of_property_read_u32(client->dev.of_node, property,
+					&prop_value);
+
+	if (!ret) {
+		if (prop_value)
+			*config |= (1 << bit_index);
+		else
+			*config &= ~(1 << bit_index);
+	}
+}
+
+/**
+ * Configures the attenuator bypasses for voltage inputs, depening on
+ * properties in the dts.
+.*
+ * The adt7473 and adt7475 only support bypassing in1.
+ *
+ * Returns a negative error code if there was an error writing to the register.
+ */
+static int load_attenuators(const struct i2c_client *client, int chip,
+				u8 *config2, u8 *config4)
+{
+	u8 conf_copy;
+	int ret = 0;
+
+	if (chip == adt7476 || chip == adt7490) {
+		conf_copy = *config4;
+
+		modify_config(client, "bypass-attenuator-in0", &conf_copy, 4);
+		modify_config(client, "bypass-attenuator-in1", &conf_copy, 5);
+		modify_config(client, "bypass-attenuator-in3", &conf_copy, 6);
+		modify_config(client, "bypass-attenuator-in4", &conf_copy, 7);
+
+		ret = i2c_smbus_write_byte_data(client, REG_CONFIG4,
+			conf_copy);
+		if (ret < 0)
+			return ret;
+
+		*config4 = conf_copy;
+	} else if (chip == adt7473 || chip == adt7475) {
+		conf_copy = *config2;
+
+		modify_config(client, "bypass-attenuator-in1", &conf_copy, 5);
+
+		ret = i2c_smbus_write_byte_data(client, REG_CONFIG2,
+			conf_copy);
+		if (ret < 0)
+			return ret;
+
+		*config2 = conf_copy;
+	}
+
+	return 0;
+}
+
 static int adt7475_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -1546,6 +1611,9 @@ static int adt7475_probe(struct i2c_client *client,
 
 	/* Voltage attenuators can be bypassed, globally or individually */
 	config2 = adt7475_read(REG_CONFIG2);
+	if (load_attenuators(client, chip, &config2, &(data->config4)) < 0)
+		dev_warn(&client->dev, "Error setting bypass attenuators\n");
+
 	if (config2 & CONFIG2_ATTN) {
 		data->bypass_attn = (0x3 << 3) | 0x3;
 	} else {
-- 
2.25.0