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 parses device tree parameter
"shunt-resistor-micro-ohms", if there is one.
Signed-off-by: Kun Yi <kunyi@xxxxxxxxxx>
---
Changes in v3:
- splitted hwmon and device tree binding patches
Documentation/hwmon/adm1275 | 3 +++
drivers/hwmon/pmbus/adm1275.c | 15 +++++++++++++--
2 files changed, 16 insertions(+), 2 deletions(-)
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;
}
--
2.19.1.331.ge82ca0e54c-goog
