The ADM series of hotswap controllers support extending
the current measurement range by using a sensing resistor
value other than the typical 1 mOhm. For example, using a 0.5 mOhm
sensing resistor doubles the maximal current can be measured.
Current driver assumes a shunt resistor value of 1 mOhm in calculation,
meaning for other resistor values, hwmon will report scaled
current/power measurements. This patch adds a device tree parameter so
that individual boards can configure its shunt resistor value.
Signed-off-by: Kun Yi <kunyi@xxxxxxxxxx>
---
.../devicetree/bindings/hwmon/adm1275.txt | 25 +++++++++++++++++++
Documentation/hwmon/adm1275 | 3 +++
drivers/hwmon/pmbus/adm1275.c | 15 +++++++++--
3 files changed, 41 insertions(+), 2 deletions(-)
create mode 100644 Documentation/devicetree/bindings/hwmon/adm1275.txt
diff --git a/Documentation/devicetree/bindings/hwmon/adm1275.txt b/Documentation/devicetree/bindings/hwmon/adm1275.txt
new file mode 100644
index 000000000000..1ecd03f3da4d
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/adm1275.txt
@@ -0,0 +1,25 @@
+adm1275 properties
+
+Required properties:
+- compatible: Must be one of the supported compatible strings:
+ - "adi,adm1075" for adm1075
+ - "adi,adm1272" for adm1272
+ - "adi,adm1275" for adm1275
+ - "adi,adm1276" for adm1276
+ - "adi,adm1278" for adm1278
+ - "adi,adm1293" for adm1293
+ - "adi,adm1294" for adm1294
+- reg: I2C address
+
+Optional properties:
+
+- shunt-resistor-micro-ohms
+ Shunt resistor value in micro-Ohm
+
+Example:
+
+adm1272@10 {
+ compatible = "adi,adm1272";
+ reg = <0x10>;
+ shunt-resistor-micro-ohms = <500>;
+};
diff --git a/Documentation/hwmon/adm1275 b/Documentation/hwmon/adm1275
index 39033538eb03..5e277b0d91ce 100644
--- a/Documentation/hwmon/adm1275
+++ b/Documentation/hwmon/adm1275
@@ -58,6 +58,9 @@ The ADM1075, unlike many other PMBus devices, does not support internal voltage
or current scaling. Reported voltages, currents, and power are raw measurements,
and will typically have to be scaled.
+The shunt value in micro-ohms can be set via device tree at compile-time. Please
+refer to the Documentation/devicetree/bindings/hwmon/adm1275.txt for bindings
+if the device tree is used.
Platform data support
---------------------
diff --git a/drivers/hwmon/pmbus/adm1275.c b/drivers/hwmon/pmbus/adm1275.c
index 13600fa79e7f..f569372c9204 100644
--- a/drivers/hwmon/pmbus/adm1275.c
+++ b/drivers/hwmon/pmbus/adm1275.c
@@ -373,6 +373,7 @@ static int adm1275_probe(struct i2c_client *client,
const struct coefficients *coefficients;
int vindex = -1, voindex = -1, cindex = -1, pindex = -1;
int tindex = -1;
+ u32 shunt;
if (!i2c_check_functionality(client->adapter,
I2C_FUNC_SMBUS_READ_BYTE_DATA
@@ -421,6 +422,13 @@ static int adm1275_probe(struct i2c_client *client,
if (!data)
return -ENOMEM;
+ if (of_property_read_u32(client->dev.of_node,
+ "shunt-resistor-micro-ohms", &shunt))
+ shunt = 1000; /* 1 mOhm if not set via DT */
+
+ if (shunt == 0)
+ return -EINVAL;
+
data->id = mid->driver_data;
info = &data->info;
@@ -654,12 +662,15 @@ static int adm1275_probe(struct i2c_client *client,
info->R[PSC_VOLTAGE_OUT] = coefficients[voindex].R;
}
if (cindex >= 0) {
- info->m[PSC_CURRENT_OUT] = coefficients[cindex].m;
+ /* Scale current with sense resistor value */
+ info->m[PSC_CURRENT_OUT] =
+ coefficients[cindex].m * shunt / 1000;
info->b[PSC_CURRENT_OUT] = coefficients[cindex].b;
info->R[PSC_CURRENT_OUT] = coefficients[cindex].R;
}
if (pindex >= 0) {
- info->m[PSC_POWER] = coefficients[pindex].m;
+ info->m[PSC_POWER] =
+ coefficients[pindex].m * shunt / 1000;
info->b[PSC_POWER] = coefficients[pindex].b;
info->R[PSC_POWER] = coefficients[pindex].R;
}
--
2.19.0.605.g01d371f741-goog
