linux-kernel - Re: [PATCH 3/5] usb: musb: ux500: add otg notifier support

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Date:	Wed, 6 Mar 2013 10:54:46 +0200
From:	Felipe Balbi <balbi@...com>
To:	Fabio Baltieri <fabio.baltieri@...aro.org>
CC:	Felipe Balbi <balbi@...com>,
	Linus Walleij <linus.walleij@...aro.org>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 3/5] usb: musb: ux500: add otg notifier support

Hi,

On Wed, Mar 06, 2013 at 09:40:28AM +0800, Fabio Baltieri wrote:
> > > Add transceiver notifier event handling to the ux500 driver to set vbus
> > > on specific transceiver events.
> > > 
> > > Acked-by: Linus Walleij <linus.walleij@...aro.org>
> > > Signed-off-by: Fabio Baltieri <fabio.baltieri@...aro.org>
> > > ---
> > >  drivers/usb/musb/ux500.c | 41 +++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 41 insertions(+)
> > > 
> > > diff --git a/drivers/usb/musb/ux500.c b/drivers/usb/musb/ux500.c
> > > index 5b742ba..b20326bb 100644
> > > --- a/drivers/usb/musb/ux500.c
> > > +++ b/drivers/usb/musb/ux500.c
> > > @@ -98,6 +98,36 @@ static void ux500_musb_set_vbus(struct musb *musb, int is_on)
> > >  		musb_readb(musb->mregs, MUSB_DEVCTL));
> > >  }
> > >  
> > > +static int musb_otg_notifications(struct notifier_block *nb,
> > > +		unsigned long event, void *unused)
> > > +{
> > > +	struct musb *musb = container_of(nb, struct musb, nb);
> > > +
> > > +	dev_dbg(musb->controller, "musb_otg_notifications %ld %s\n",
> > > +			event, otg_state_string(musb->xceiv->state));
> > > +
> > > +	switch (event) {
> > > +	case USB_EVENT_ID:
> > > +		dev_dbg(musb->controller, "ID GND\n");
> > > +		ux500_musb_set_vbus(musb, 1);
> > > +		break;
> > > +	case USB_EVENT_VBUS:
> > > +		dev_dbg(musb->controller, "VBUS Connect\n");
> > 
> > are you sure this is correct ? you're not doing anything in case of
> > vbus event. Shouldn't you make sure your vbus is off ?
> 
> The implementation I'm taking as reference for this patches does not do
> anything on VBUS event and as I can see from commmit history, it has
> been based on the omap2430 one, that in turns used to just run phy_init
> - and that's not implemented.  But...
> 
> > What if your user uses a non-standard cable which has id-pin grounded
> > on both sides ?
> 
> A cable with two micro/mini connectors with grounded IDs?  Did you ever
> encountered such a thing?  I guess a ux500_musb_set_vbus(musb, 0) would

in fact, no...

> not hurt in that case.

right, just to be sure. Maybe I should fix omap2430 as well. I'll add it
to my TODO list.

-- 
balbi

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