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

[Diogo Ivo]

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@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.

Ok, then I'll do just that.

> Jon