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

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Message-ID: <dcfe4159-48ad-4b28-ae3a-388e6d0f229a@tecnico.ulisboa.pt>
Date: Tue, 13 Jan 2026 13:30:02 +0000
From: Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
To: Vinod Koul <vkoul@...nel.org>, Jonathan Hunter <jonathanh@...dia.com>
Cc: Mathias Nyman <mathias.nyman@...el.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Thierry Reding <thierry.reding@...il.com>, JC Kuo <jckuo@...dia.com>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, linux-usb@...r.kernel.org,
 linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-phy@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/5] phy: tegra: xusb: Fix USB2 port regulator disable
 logic



On 12/24/25 07:27, Vinod Koul wrote:
> On 04-12-25, 21:27, Diogo Ivo wrote:
>> 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.
> 
> Never mix a patch with something else please. More imp if it is fix
> which will go to rcX. Please send a different patch for typo

Ok, will split for v2.

>> 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;
>>   };
> 
> Jonathan can we get some t-b for these two patches
>