linux-kernel - [PATCH 2/2] hwmon: (pmbus/bpa-rs600) Add workaround for incorrect Pin max

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Message-Id: <20210811041738.15061-3-chris.packham@alliedtelesis.co.nz>
Date:   Wed, 11 Aug 2021 16:17:38 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     linux@...ck-us.net, jdelvare@...e.com
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH 2/2] hwmon: (pmbus/bpa-rs600) Add workaround for incorrect Pin max

BPD-RS600 modules running firmware v5.70 misreport the MFR_PIN_MAX.
The indicate a maximum of 1640W instead of 700W. Detect the invalid
reading and return a sensible value instead.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
 drivers/hwmon/pmbus/bpa-rs600.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/pmbus/bpa-rs600.c b/drivers/hwmon/pmbus/bpa-rs600.c
index d495faa89799..f4baed9ce8a4 100644
--- a/drivers/hwmon/pmbus/bpa-rs600.c
+++ b/drivers/hwmon/pmbus/bpa-rs600.c
@@ -65,6 +65,24 @@ static int bpa_rs600_read_vin(struct i2c_client *client)
 	return ret;
 }
 
+/*
+ * The firmware on some BPD-RS600 models incorrectly reports 1640W
+ * for MFR_PIN_MAX. Deal with this by returning a sensible value.
+ */
+static int bpa_rs600_read_pin_max(struct i2c_client *client)
+{
+	int ret;
+
+	ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_PIN_MAX);
+	if (ret < 0)
+		return ret;
+
+	if (ret == 0x0b34)
+		return 0x095e;
+
+	return ret;
+}
+
 static int bpa_rs600_read_word_data(struct i2c_client *client, int page, int phase, int reg)
 {
 	int ret;
@@ -92,7 +110,8 @@ static int bpa_rs600_read_word_data(struct i2c_client *client, int page, int pha
 		ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_IOUT_MAX);
 		break;
 	case PMBUS_PIN_OP_WARN_LIMIT:
-		ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_PIN_MAX);
+	case PMBUS_MFR_PIN_MAX:
+		ret = bpa_rs600_read_pin_max(client);
 		break;
 	case PMBUS_POUT_OP_WARN_LIMIT:
 		ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_POUT_MAX);
-- 
2.32.0