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: 15b2703e5e02 ("hwmon: (pmbus) Add driver for BluTek BPA-RS600")
Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
---
drivers/hwmon/pmbus/bpa-rs600.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/drivers/hwmon/pmbus/bpa-rs600.c b/drivers/hwmon/pmbus/bpa-rs600.c
index f6558ee9dec3..2be69fedfa36 100644
--- a/drivers/hwmon/pmbus/bpa-rs600.c
+++ b/drivers/hwmon/pmbus/bpa-rs600.c
@@ -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;
--
2.31.1
