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

[Jon Hunter]

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@xxxxxxxxxxxxxxxxxx>
> > > ---
> > >   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.

Jon

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