Re: [PATCH v2 2/6] usb: xhci: tegra: Remove redundant mutex when setting phy mode

[Diogo Ivo]

Hello,

On 3/24/26 11:48, Thierry Reding wrote:
> On Tue, Jan 27, 2026 at 03:11:48PM +0000, Diogo Ivo wrote:
> > As the PHY subsystem already synchronizes concurrent accesses to a PHY
> > instance with a core-internal mutex remove the driver specific mutex
> > synchronization.
> >
> > Signed-off-by: Diogo Ivo <diogo.ivo@xxxxxxxxxxxxxxxxxx>
> > ---
> > v1->v2:
> > - New patch
> > ---
> >   drivers/usb/host/xhci-tegra.c | 4 ----
> >   1 file changed, 4 deletions(-)
> >
> > diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
> > index 8b492871d21d..927861ca14f2 100644
> > --- a/drivers/usb/host/xhci-tegra.c
> > +++ b/drivers/usb/host/xhci-tegra.c
> > @@ -1357,15 +1357,11 @@ static void tegra_xhci_id_work(struct work_struct *work)
> >   
> >   	dev_dbg(tegra->dev, "host mode %s\n", str_on_off(tegra->host_mode));
> >   
> > -	mutex_lock(&tegra->lock);
> > -
> >   	if (tegra->host_mode)
> >   		phy_set_mode_ext(phy, PHY_MODE_USB_OTG, USB_ROLE_HOST);
> >   	else
> >   		phy_set_mode_ext(phy, PHY_MODE_USB_OTG, USB_ROLE_NONE);
> >   
> > -	mutex_unlock(&tegra->lock);
> > -
>
> It looks to me like the mutex here is trying to protect against
> tegra->host_mode changing while we're setting a different mode. That
> doesn't seem to be taken care of by the PHY internal mutex.

After taking another look at it I think I understand your point for the
mutex, but in that case wouldn't it also need to be held in the writer
of host_mode, tegra_xhci_id_notify()?

This patch has been picked up as-is into usb-next so it would be nice to
figure this out before it gets merged in the next merge window.

Diogo

> Thierry