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hwmon: (pmbus/bpa-rs600) Handle Vin readings >= 256V

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The BPA-RS600 doesn't follow the PMBus spec for linear data.
Specifically it treats the mantissa as an unsigned 11-bit value instead
of a two's complement 11-bit value. At this point it's unclear whether
this only affects Vin or if Pin/Pout1 are affected as well. Erring on
the side of caution only Vin is dealt with here.

Fixes: 15b2703e5e ("hwmon: (pmbus) Add driver for BluTek BPA-RS600")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20210616034218.25821-1-chris.packham@alliedtelesis.co.nz
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Chris Packham 2021-06-16 15:42:18 +12:00 committed by Guenter Roeck
parent 009c9aa5be
commit 6e9ef8ca68
1 changed files with 29 additions and 0 deletions
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29
drivers/hwmon/pmbus/bpa-rs600.c
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@ -46,6 +46,32 @@ static int bpa_rs600_read_byte_data(struct i2c_client *client, int page, int reg
return ret;
}
/*
* The BPA-RS600 violates the PMBus spec. Specifically it treats the
* mantissa as unsigned. Deal with this here to allow the PMBus core
* to work with correctly encoded data.
*/
static int bpa_rs600_read_vin(struct i2c_client *client)
{
int ret, exponent, mantissa;
ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_READ_VIN);
if (ret < 0)
return ret;
if (ret & BIT(10)) {
exponent = ret >> 11;
mantissa = ret & 0x7ff;
exponent++;
mantissa >>= 1;
ret = (exponent << 11) | mantissa;
}
return ret;
}
static int bpa_rs600_read_word_data(struct i2c_client *client, int page, int phase, int reg)
{
int ret;
@ -85,6 +111,9 @@ static int bpa_rs600_read_word_data(struct i2c_client *client, int page, int pha
/* These commands return data but it is invalid/un-documented */
ret = -ENXIO;
break;
case PMBUS_READ_VIN:
ret = bpa_rs600_read_vin(client);
break;
default:
if (reg >= PMBUS_VIRT_BASE)
ret = -ENXIO;