From 6e5c06ad94115e58e4f274bdaed2618b1e39ac38 Mon Sep 17 00:00:00 2001 From: Kun Yi Date: Wed, 17 Oct 2018 15:26:39 -0700 Subject: hwmon: (adm1275) Allow setting shunt reg value 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 Signed-off-by: Guenter Roeck --- 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; } -- cgit v1.2.1