linux-kernel - Re: [PATCH] usb: musb: Disable pullup in gadget setup

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Date:   Tue, 30 Apr 2019 10:10:43 -0500
From:   Bin Liu <b-liu@...com>
To:     Paul Cercueil <paul@...pouillou.net>, <od@...c.me>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: musb: Disable pullup in gadget setup

On Tue, Apr 30, 2019 at 10:05:06AM -0500, Bin Liu wrote:
> Hi Paul,
> 
> On Thu, Apr 04, 2019 at 11:10:46AM -0500, Bin Liu wrote:
> > On Thu, Apr 04, 2019 at 11:37:43AM +0200, Paul Cercueil wrote:
> > > The pullup may be already enabled before the driver is initialized.
> > > It has to be disabled at init time, as we cannot guarantee that a gadget
> > > driver will be bound to the UDC.
> > > 
> > > Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> > > ---
> > >  drivers/usb/musb/musb_gadget.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> > > index ffe462a657b1..094dc59c834c 100644
> > > --- a/drivers/usb/musb/musb_gadget.c
> > > +++ b/drivers/usb/musb/musb_gadget.c
> > > @@ -1794,6 +1794,7 @@ int musb_gadget_setup(struct musb *musb)
> > >  
> > >  	musb->is_active = 0;
> > >  	musb_platform_try_idle(musb, 0);
> > > +	musb_pullup(musb, 0);
> > >  
> > >  	status = usb_add_gadget_udc(musb->controller, &musb->g);
> > >  	if (status)
> > 
> > Applied.
> 
> Sorry, I have dropped this patch from my tree. I realized the gadget
> core already defines callbacks to control the pullup. I think the
> proper fix should be calling usb_udc_vbus_handler() in musb gadget or
> glue layers.

Basically besides the problem your patch tries to fix, there is another
problem related to the pullup, which is enabled right after bind a
gadget driver, regardless of vbus status. This violates the USB Spec.
Implementing the udc core callbacks should fix both issues.

-Bin.