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

Diogo Ivo
2026-01-13T15:05:22Z

On 1/13/26 14:42, Jon Hunter wrote:
>
> On 13/01/2026 13:59, Diogo Ivo wrote:
>>
>>
>> On 1/13/26 12:01, Jon Hunter wrote:
>>>
>>> On 04/12/2025 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.
>>>>
>>>> Signed-off-by: Diogo Ivo <diogo.ivo@tecnico.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;
>>>> };
>>>
>>>
>>> A similar fix was made to the Tegra186 code by commit cefc1caee9dd
>>> ("phy: tegra: xusb: Fix unbalanced regulator disable in UTMI PHY
>>> mode"). Although the above looks simpler, I am wondering if we should
>>> make a similar change to the Tegra210 code so that they both are
>>> implemented in the same way?
>>
>> Looking at cefc1caee9dd my approach leads to less changes but I do agree
>> that standardization benefits us here. However in that case I think we
>> can take it a step further and actually just have a single function
>> tegra_xusb_padctl_id_override() (and likewise for vbus_override() and
>> set_mode()) since they all seem to do the same thing in both platforms.
>
> Yes I think that would be fine. I can't say I have looked at that in
> detail but that would seem like the logical way to go.

Ok, then I'll do just that.

> Jon