[PATCH 1/1] phy: tegra: xusb: Fix unbalanced regulator disable in UTMI PHY mode

[Wayne Chang <waynec@nvidia.com>]

When transitioning from USB_ROLE_DEVICE to USB_ROLE_NONE, the code
assumed that the regulator should be disabled. However, if the regulator
is marked as always-on, regulator_is_enabled() continues to return true,
leading to an incorrect attempt to disable a regulator which is not
enabled.

This can result in warnings such as:

[  250.155624] WARNING: CPU: 1 PID: 7326 at drivers/regulator/core.c:3004
_regulator_disable+0xe4/0x1a0
[  250.155652] unbalanced disables for VIN_SYS_5V0

To fix this, we move the regulator control logic into
tegra186_xusb_padctl_id_override() function since it's directly related
to the ID override state. The regulator is now only disabled when the role
transitions from USB_ROLE_HOST to USB_ROLE_NONE, by checking the VBUS_ID
register. This ensures that regulator enable/disable operations are
properly balanced and only occur when actually transitioning to/from host
mode.

Fixes: 49d46e3c7e59 ("phy: tegra: xusb: Add set_mode support for UTMI phy on Tegra186")
Cc: stable@vger.kernel.org
Signed-off-by: Wayne Chang <waynec@nvidia.com>
---
 drivers/phy/tegra/xusb-tegra186.c | 59 +++++++++++++++++++------------
 1 file changed, 37 insertions(+), 22 deletions(-)

diff --git a/drivers/phy/tegra/xusb-tegra186.c b/drivers/phy/tegra/xusb-tegra186.c
index fae6242aa730..1b35d50821f7 100644
--- a/drivers/phy/tegra/xusb-tegra186.c
+++ b/drivers/phy/tegra/xusb-tegra186.c
@@ -774,13 +774,15 @@ static int tegra186_xusb_padctl_vbus_override(struct tegra_xusb_padctl *padctl,
 }
 
 static int tegra186_xusb_padctl_id_override(struct tegra_xusb_padctl *padctl,
-					    bool status)
+					    struct tegra_xusb_usb2_port *port, bool status)
 {
-	u32 value;
+	u32 value, id_override;
+	int err = 0;
 
 	dev_dbg(padctl->dev, "%s id override\n", status ? "set" : "clear");
 
 	value = padctl_readl(padctl, USB2_VBUS_ID);
+	id_override = value & ID_OVERRIDE(~0);
 
 	if (status) {
 		if (value & VBUS_OVERRIDE) {
@@ -791,15 +793,35 @@ static int tegra186_xusb_padctl_id_override(struct tegra_xusb_padctl *padctl,
 			value = padctl_readl(padctl, USB2_VBUS_ID);
 		}
 
-		value &= ~ID_OVERRIDE(~0);
-		value |= ID_OVERRIDE_GROUNDED;
+		if (id_override != ID_OVERRIDE_GROUNDED) {
+			value &= ~ID_OVERRIDE(~0);
+			value |= ID_OVERRIDE_GROUNDED;
+			padctl_writel(padctl, value, USB2_VBUS_ID);
+
+			err = regulator_enable(port->supply);
+			if (err) {
+				dev_err(padctl->dev, "Failed to enable regulator: %d\n", err);
+				return err;
+			}
+		}
 	} else {
-		value &= ~ID_OVERRIDE(~0);
-		value |= ID_OVERRIDE_FLOATING;
+		if (id_override == ID_OVERRIDE_GROUNDED) {
+			/*
+			 * The regulator is disabled only when the role transitions
+			 * from USB_ROLE_HOST to USB_ROLE_NONE.
+			 */
+			err = regulator_disable(port->supply);
+			if (err) {
+				dev_err(padctl->dev, "Failed to disable regulator: %d\n", err);
+				return err;
+			}
+
+			value &= ~ID_OVERRIDE(~0);
+			value |= ID_OVERRIDE_FLOATING;
+			padctl_writel(padctl, value, USB2_VBUS_ID);
+		}
 	}
 
-	padctl_writel(padctl, value, USB2_VBUS_ID);
-
 	return 0;
 }
 
@@ -818,27 +840,20 @@ static int tegra186_utmi_phy_set_mode(struct phy *phy, enum phy_mode mode,
 
 	if (mode == PHY_MODE_USB_OTG) {
 		if (submode == USB_ROLE_HOST) {
-			tegra186_xusb_padctl_id_override(padctl, true);
-
-			err = regulator_enable(port->supply);
+			err = tegra186_xusb_padctl_id_override(padctl, port, true);
+			if (err)
+				goto out;
 		} else if (submode == USB_ROLE_DEVICE) {
 			tegra186_xusb_padctl_vbus_override(padctl, true);
 		} else if (submode == USB_ROLE_NONE) {
-			/*
-			 * When port is peripheral only or role transitions to
-			 * USB_ROLE_NONE from USB_ROLE_DEVICE, regulator is not
-			 * enabled.
-			 */
-			if (regulator_is_enabled(port->supply))
-				regulator_disable(port->supply);
-
-			tegra186_xusb_padctl_id_override(padctl, false);
+			err = tegra186_xusb_padctl_id_override(padctl, port, false);
+			if (err)
+				goto out;
 			tegra186_xusb_padctl_vbus_override(padctl, false);
 		}
 	}
-
+out:
 	mutex_unlock(&padctl->lock);
-
 	return err;
 }
 
-- 
2.25.1