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hwmon: (adm1275) Allow setting shunt reg value

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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@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Kun Yi
2018-10-17 15:26:39 -07:00
committed by Guenter Roeck
parent f567035a61
commit 6e5c06ad94
2 changed files with 16 additions and 2 deletions
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15
drivers/hwmon/pmbus/adm1275.c
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@@ -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;
}