linux-kernel - [PATCH 2/2] iio: si7020: Lock root adapter to wait for reset

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Message-Id: <20220526205334.64114-3-eajames@linux.ibm.com>
Date:   Thu, 26 May 2022 15:53:34 -0500
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-i2c@...r.kernel.org
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        wsa@...nel.org, peda@...ntia.se, jic23@...nel.org, lars@...afoo.de,
        eajames@...ux.ibm.com, miltonm@...ibm.com, joel@....id.au
Subject: [PATCH 2/2] iio: si7020: Lock root adapter to wait for reset

Use the new mux root operations to lock the root adapter while waiting for
the reset to complete. I2C commands issued after the SI7020 is starting up
or after reset can potentially upset the startup sequence. Therefore, the
host needs to wait for the startup sequence to finish before issuing
further I2C commands.

Signed-off-by: Eddie James <eajames@...ux.ibm.com>
---
 drivers/iio/humidity/si7020.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c
index ab6537f136ba..76ca7863f35b 100644
--- a/drivers/iio/humidity/si7020.c
+++ b/drivers/iio/humidity/si7020.c
@@ -106,6 +106,7 @@ static const struct iio_info si7020_info = {
 static int si7020_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
+	struct i2c_adapter *root;
 	struct iio_dev *indio_dev;
 	struct i2c_client **data;
 	int ret;
@@ -115,13 +116,24 @@ static int si7020_probe(struct i2c_client *client,
 				     I2C_FUNC_SMBUS_READ_WORD_DATA))
 		return -EOPNOTSUPP;
 
+	root = i2c_lock_select_bus(client->adapter);
+	if (IS_ERR(root))
+		return PTR_ERR(root);
+
 	/* Reset device, loads default settings. */
-	ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
-	if (ret < 0)
+	ret = __i2c_smbus_xfer(root, client->addr, client->flags,
+			       I2C_SMBUS_WRITE, SI7020CMD_RESET,
+			       I2C_SMBUS_BYTE, NULL);
+	if (ret < 0) {
+		i2c_unlock_deselect_bus(client->adapter);
 		return ret;
+	}
+
 	/* Wait the maximum power-up time after software reset. */
 	msleep(15);
 
+	i2c_unlock_deselect_bus(client->adapter);
+
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;
-- 
2.27.0