linux-kernel - [PATCH 2/5] phy: tegra: xusb: Fix USB2 port regulator disable logic

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Message-Id: <20251204-diogo-tegra_phy-v1-2-51a2016d0be8@tecnico.ulisboa.pt>
Date: Thu, 04 Dec 2025 21:27:18 +0000
From: Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
To: Mathias Nyman <mathias.nyman@...el.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Thierry Reding <thierry.reding@...il.com>, 
 Jonathan Hunter <jonathanh@...dia.com>, JC Kuo <jckuo@...dia.com>, 
 Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-usb@...r.kernel.org, linux-tegra@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org, 
 devicetree@...r.kernel.org, Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
Subject: [PATCH 2/5] phy: tegra: xusb: Fix USB2 port regulator disable
 logic

The USB2 PHY mode handling on Tegra210 incorrectly relied on
regulator_is_enabled() when determining whether the VBUS supply should
be disabled during role changes. This is because regulator_is_enabled()
reports exactly what is states and not if there is an unbalanced number
of calls between regulator_enable() and regulator_disable(). For
example, regulator_is_enabled() always reports true on a fixed-regulator
with no enable gpio, which is the case on the Pixel C.

This then leads to the PHY driver wrongfully calling regulator_disable()
when transitioning from USB_ROLE_DEVICE to USB_ROLE_NONE since the driver
did not previously call the corresponding regulator_enable().

Fix this by keeping track of the current role and updating the logic to
disable the regulator only when the previous role was USB_ROLE_HOST.

While at it fix a small typo in a comment.

Signed-off-by: Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
---
 drivers/phy/tegra/xusb-tegra210.c | 5 +++--
 drivers/phy/tegra/xusb.h          | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/tegra/xusb-tegra210.c b/drivers/phy/tegra/xusb-tegra210.c
index 3409924498e9..63ad57d95514 100644
--- a/drivers/phy/tegra/xusb-tegra210.c
+++ b/drivers/phy/tegra/xusb-tegra210.c
@@ -1934,9 +1934,9 @@ static int tegra210_usb2_phy_set_mode(struct phy *phy, enum phy_mode mode,
 			/*
 			 * When port is peripheral only or role transitions to
 			 * USB_ROLE_NONE from USB_ROLE_DEVICE, regulator is not
-			 * be enabled.
+			 * enabled.
 			 */
-			if (regulator_is_enabled(port->supply))
+			if (port->role == USB_ROLE_HOST)
 				regulator_disable(port->supply);
 
 			tegra210_xusb_padctl_id_override(padctl, false);
@@ -1944,6 +1944,7 @@ static int tegra210_usb2_phy_set_mode(struct phy *phy, enum phy_mode mode,
 		}
 	}
 
+	port->role = submode;
 	mutex_unlock(&padctl->lock);
 
 	return err;
diff --git a/drivers/phy/tegra/xusb.h b/drivers/phy/tegra/xusb.h
index d2b5f9565132..273af147dfd3 100644
--- a/drivers/phy/tegra/xusb.h
+++ b/drivers/phy/tegra/xusb.h
@@ -317,6 +317,7 @@ struct tegra_xusb_usb2_port {
 	enum usb_dr_mode mode;
 	bool internal;
 	int usb3_port_fake;
+	enum usb_role role;
 };
 
 static inline struct tegra_xusb_usb2_port *

-- 
2.52.0