net: pse-pd: tps23881: Fix power on/off issue

An issue was present in the initial driver implementation. The driver
read the power status of all channels before toggling the bit of the
desired one. Using the power status register as a base value introduced
a problem, because only the bit corresponding to the concerned channel ID
should be set in the write-only power enable register. This led to cases
where disabling power for one channel also powered off other channels.

This patch removes the power status read and ensures the value is
limited to the bit matching the channel index of the PI.

Fixes: 20e6d19 ("net: pse-pd: Add TI TPS23881 PSE controller driver")
Signed-off-by: Kory Maincent <[email protected]>
Acked-by: Oleksij Rempel <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

drivers/net/pse-pd/tps23881.c

@@ -64,15 +64,11 @@ static int tps23881_pi_enable(struct pse_controller_dev *pcdev, int id)
 	if (id >= TPS23881_MAX_CHANS)
 		return -ERANGE;
 
-	ret = i2c_smbus_read_word_data(client, TPS23881_REG_PW_STATUS);
-	if (ret < 0)
-		return ret;
-
 	chan = priv->port[id].chan[0];
 	if (chan < 4)
-		val = (u16)(ret | BIT(chan));
+		val = BIT(chan);
 	else
-		val = (u16)(ret | BIT(chan + 4));
+		val = BIT(chan + 4);
 
 	if (priv->port[id].is_4p) {
 		chan = priv->port[id].chan[1];
@@ -100,15 +96,11 @@ static int tps23881_pi_disable(struct pse_controller_dev *pcdev, int id)
 	if (id >= TPS23881_MAX_CHANS)
 		return -ERANGE;
 
-	ret = i2c_smbus_read_word_data(client, TPS23881_REG_PW_STATUS);
-	if (ret < 0)
-		return ret;
-
 	chan = priv->port[id].chan[0];
 	if (chan < 4)
-		val = (u16)(ret | BIT(chan + 4));
+		val = BIT(chan + 4);
 	else
-		val = (u16)(ret | BIT(chan + 8));
+		val = BIT(chan + 8);
 
 	if (priv->port[id].is_4p) {
 		chan = priv->port[id].chan[1];