Re: [PATCH 1/2 v2] hwmon: (ltc4151) Make shunt-resistor configurable

Hi Guenter,

On Sat, Jul 30, 2016 at 09:00:14AM -0700, Guenter Roeck wrote:

Daniel,

On 07/25/2016 04:56 AM, Daniel Golle wrote:

quoted

Allow to specify the resistance of the attached shunt via DT by
adding the shunt-resistor property. Fall-back to the previous
default (1 mOhm) if unset.

Signed-off-by: Daniel Golle <redacted>

Please resend with the property name changed as asked for by Rob.

Ok, will do. I originally copy-pasted the property name from ina209,
so I reckon it's supposed to be changed there as well...?

Cheers

Daniel

Thanks,
Guenter

quoted

---
v2: removed unneeded things and throw -EINVAL for shunt==0

  drivers/hwmon/ltc4151.c | 21 +++++++++++++++++++--
  1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/ltc4151.c b/drivers/hwmon/ltc4151.c
index c86a184..419c6f7 100644
--- a/drivers/hwmon/ltc4151.c
+++ b/drivers/hwmon/ltc4151.c

@@ -30,6 +30,7 @@

  #include <linux/kernel.h>
  #include <linux/module.h>
+#include <linux/of.h>
  #include <linux/init.h>
  #include <linux/err.h>
  #include <linux/slab.h>

@@ -52,6 +53,7 @@ struct ltc4151_data {
  	struct mutex update_lock;
  	bool valid;
  	unsigned long last_updated; /* in jiffies */
+	unsigned int shunt; /* in micro ohms */

  	/* Registers */
  	u8 regs[6];

@@ -111,9 +113,9 @@ static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
  	case LTC4151_SENSE_H:
  		/*
  		 * 20uV resolution. Convert to current as measured with
-		 * an 1 mOhm sense resistor, in mA.
+		 * a given sense resistor, in mA.
  		 */
-		val = val * 20;
+		val = val * 20 * 1000 / data->shunt;
  		break;
  	case LTC4151_VIN_H:
  		/* 25 mV per increment */

@@ -176,6 +178,7 @@ static int ltc4151_probe(struct i2c_client *client,
  	struct device *dev = &client->dev;
  	struct ltc4151_data *data;
  	struct device *hwmon_dev;
+	u32 shunt;

  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
  		return -ENODEV;

@@ -184,6 +187,14 @@ static int ltc4151_probe(struct i2c_client *client,
  	if (!data)
  		return -ENOMEM;

+	if (of_property_read_u32(client->dev.of_node, "shunt-resistor", &shunt))
+		shunt = 1000; /* 1 mOhm if not set via DT */
+
+	if (shunt == 0)
+		return -EINVAL;
+
+	data->shunt = shunt;
+
  	data->client = client;
  	mutex_init(&data->update_lock);

@@ -199,10 +210,16 @@ static const struct i2c_device_id ltc4151_id[] = {
  };
  MODULE_DEVICE_TABLE(i2c, ltc4151_id);

+static const struct of_device_id ltc4151_match[] = {
+	{ .compatible = "lltc,ltc4151" },
+	{},
+};
+
  /* This is the driver that will be inserted */
  static struct i2c_driver ltc4151_driver = {
  	.driver = {
  		.name	= "ltc4151",
+		.of_match_table = of_match_ptr(ltc4151_match),
  	},
  	.probe		= ltc4151_probe,
  	.id_table	= ltc4151_id,

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