[PATCH v4 1/2] hwmon: (adt7475) Added attenuator bypass support

Logan Shaw
2020-01-20T00:17:24Z

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@alliedtelesis.co.nz>
---
---
drivers/hwmon/adt7475.c | 76 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)

diff --git a/drivers/hwmon/adt7475.c b/drivers/hwmon/adt7475.c
index 6c64d50c9aae..2bb787acb363 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 +1458,76 @@ static int adt7475_update_limits(struct i2c_client *client)
return 0;
}

+/**
+ * Attempts to read a u32 property from the DTS, if there is no error and
+ * the properties value is zero then the bit given by parameter bit_index
+ * is cleared in the parameter config. If the value is non-zero then the bit
+ * is set.
+ *
+ * If reading the dts property returned an error code then it is returned and
+ * the config parameter is not modified.
+ */
+static int modify_config_from_dts_prop(const struct i2c_client *client,
+ char *dts_property, u8 *config, u8 bit_index) {
+ u32 is_attenuator_bypassed = 0;
+ int ret = of_property_read_u32(client->dev.of_node, dts_property,
+ &is_attenuator_bypassed);
+
+ if (! ret) {
+ if (is_attenuator_bypassed)
+ *config |= (1 << bit_index);
+ else
+ *config &= ~(1 << bit_index);
+ }
+
+ return ret;
+}
+
+/**
+ * Reads all individual voltage input bypass attenuator properties from the
+ * DTS, and if the property is present the corresponding bit is set in the
+ * register.
+
+ * Properties are in the form of "bypass-attenuator-inx", where x is an
+ * integer from the set {0, 1, 3, 4} (can not bypass in2 attenuator).
+.*
+ * 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_all_bypass_attenuators(const struct i2c_client *client,
+ int chip, u8 *config2, u8 *config4)
+{
+ u8 config2_copy = *config2;
+ u8 config4_copy = *config4;
+
+ if (chip == adt7476 || chip == adt7490) {
+ modify_config_from_dts_prop(client, "bypass-attenuator-in0",
+ &config4_copy, 4);
+ modify_config_from_dts_prop(client, "bypass-attenuator-in1",
+ &config4_copy, 5);
+ modify_config_from_dts_prop(client, "bypass-attenuator-in3",
+ &config4_copy, 6);
+ modify_config_from_dts_prop(client, "bypass-attenuator-in4",
+ &config4_copy, 7);
+
+ if (i2c_smbus_write_byte_data(client, REG_CONFIG4, config4_copy) < 0)
+ return -EREMOTEIO;
+
+ *config4 = config4_copy;
+ } else if (chip == adt7473 || chip == adt7475) {
+ modify_config_from_dts_prop(client, "bypass-attenuator-in1",
+ &config2_copy, 5);
+
+ if (i2c_smbus_write_byte_data(client, REG_CONFIG2, config2_copy) < 0)
+ return -EREMOTEIO;
+
+ *config2 = config2_copy;
+ }
+
+ return 0;
+}
+
static int adt7475_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
@@ -1546,6 +1617,11 @@ static int adt7475_probe(struct i2c_client *client,

/* Voltage attenuators can be bypassed, globally or individually */
config2 = adt7475_read(REG_CONFIG2);
+ if (load_all_bypass_attenuators(client, chip,
+ &config2, &(data->config4)) < 0)
+ dev_warn(&client->dev,
+ "Error setting bypass attenuator bits\n");
+
if (config2 & CONFIG2_ATTN) {
data->bypass_attn = (0x3 << 3) | 0x3;
} else {
--
2.25.0