[PATCH v2 1/2] hwmon: (pmbus/tps53679) Select page 0 for single-page TPS53676

["Pradhan, Sanman" <sanman.pradhan@hpe.com>]

From: Sanman Pradhan <psanman@juniper.net>

tps53676_identify() derives the number of PMBus pages but does not
ensure that page 0 is selected for single-page configurations.
pmbus_set_page() does not update the PAGE register when info->pages is
1, so if boot firmware leaves PAGE set to another value subsequent
register accesses may target the wrong page.

For single-page devices, select page 0 explicitly.

Fixes: cb3d37b59012 ("hwmon: (pmbus/tps53679) Add support for TI TPS53676")
Cc: stable@vger.kernel.org
Signed-off-by: Sanman Pradhan <psanman@juniper.net>
---
 drivers/hwmon/pmbus/tps53679.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/hwmon/pmbus/tps53679.c b/drivers/hwmon/pmbus/tps53679.c
index dcd4250b679d..4f91b0a43ad0 100644
--- a/drivers/hwmon/pmbus/tps53679.c
+++ b/drivers/hwmon/pmbus/tps53679.c
@@ -246,6 +246,15 @@ static int tps53676_identify(struct i2c_client *client,
 	if (phases_b > 0) {
 		info->pages = 2;
 		info->phases[1] = phases_b;
+	} else {
+		/*
+		 * pmbus_set_page() does not update the PAGE register on
+		 * single-page devices, so select page 0 explicitly in case
+		 * the boot firmware left the device on another page.
+		 */
+		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
+		if (ret < 0)
+			return ret;
 	}
 
 	return 0;
-- 
2.34.1