linux-kernel - [PATCH v2] Fix FSP-3Y YH-5151E non-compliant vout encoding

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Message-Id: <20210428083833.4136346-1-kubernat@cesnet.cz>
Date:   Wed, 28 Apr 2021 10:38:32 +0200
From:   Václav Kubernát <kubernat@...net.cz>
To:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Václav Kubernát <kubernat@...net.cz>
Subject: [PATCH v2] Fix FSP-3Y YH-5151E non-compliant vout encoding

I didn't properly test the driver for YH-5151E, so it was completely
broken. Firstly, the log/real mapping was incorrect in one case.
Secondly, PMBus specifies that output voltages should be in the linear16
encoding. However, the PDU is non-compliant and uses linear11. YM-2151E
isn't affected by this. Fix this by converting the values inside the
read functions. linear16 gets the exponent from the VOUT_MODE command.
The device doesn't support it, so I have to manually supply the value
for it.

Both supported devices have now been tested to report correct vout
values.

Signed-off-by: Václav Kubernát <kubernat@...net.cz>
---
 drivers/hwmon/pmbus/fsp-3y.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/pmbus/fsp-3y.c b/drivers/hwmon/pmbus/fsp-3y.c
index 564649e87e34..dc147a79d6aa 100644
--- a/drivers/hwmon/pmbus/fsp-3y.c
+++ b/drivers/hwmon/pmbus/fsp-3y.c
@@ -57,7 +57,7 @@ static int page_log_to_page_real(int page_log, enum chips chip)
 		case YH5151E_PAGE_12V_LOG:
 			return YH5151E_PAGE_12V_REAL;
 		case YH5151E_PAGE_5V_LOG:
-			return YH5151E_PAGE_5V_LOG;
+			return YH5151E_PAGE_5V_REAL;
 		case YH5151E_PAGE_3V3_LOG:
 			return YH5151E_PAGE_3V3_REAL;
 		}
@@ -103,17 +103,28 @@ static int set_page(struct i2c_client *client, int page_log)
 
 static int fsp3y_read_byte_data(struct i2c_client *client, int page, int reg)
 {
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct fsp3y_data *data = to_fsp3y_data(info);
 	int rv;
 
 	rv = set_page(client, page);
 	if (rv < 0)
 		return rv;
 
+	/*
+	 * YH5151-E outputs vout in linear11. The conversion is done later, but
+	 * I have to inject pmbus_core with the correct exponent.
+	 */
+	if (data->chip == yh5151e && reg == PMBUS_VOUT_MODE)
+		return 0x1A;
+
 	return i2c_smbus_read_byte_data(client, reg);
 }
 
 static int fsp3y_read_word_data(struct i2c_client *client, int page, int phase, int reg)
 {
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct fsp3y_data *data = to_fsp3y_data(info);
 	int rv;
 
 	/*
@@ -144,7 +155,18 @@ static int fsp3y_read_word_data(struct i2c_client *client, int page, int phase,
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_read_word_data(client, reg);
+	rv = i2c_smbus_read_word_data(client, reg);
+	if (rv < 0)
+		return rv;
+
+	/*
+	 * The PDU is non-compliant and outputs output voltages in linear11
+	 * instead of linear16.
+	 */
+	if (data->chip == yh5151e && reg == PMBUS_READ_VOUT)
+		rv = ((s16)((rv & 0x7ff) << 5)) >> 5;
+
+	return rv;
 }
 
 struct pmbus_driver_info fsp3y_info[] = {
-- 
2.31.1