Re: [PATCH RFC] usb: chipidea: add support for usb_phy in generic usb2

[Baruch Siach]

Hi Kishon,

On Mon, Jan 05, 2015 at 11:09:35AM +0530, Kishon Vijay Abraham I wrote:
> On Sunday 04 January 2015 11:58 AM, Baruch Siach wrote:
> > Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx>
> > ---
> >  drivers/usb/chipidea/ci_hdrc_usb2.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > I'm sending this as RFC as I'm not sure this is the right thing to do. There
> > seems to be a move away from USB specific PHY drivers towards the generic PHY
> > framework (drivers/phy). The trouble is that my PHY is similar to the mxs PHY
> > (phy-mxs-usb.c), and like mxs I need the notify_connect/notify_disconnect
> > callbacks. This functionality is not available is the generic PHY
> > framework. Having support for both 'usb-phy' and 'phy' properties (as dwc3
> > seems to do) is particularly bad, since the distinction between the two is a
> > Linux implementation detail that has nothing to do with hardware description.
> > 
> > So my questions are:
> > 
> >    1. Is there a plan to add notifications support to the generic PHY?
> > 
> >    2. If not, what are my options?
> 
> extcon framework has notification support. I feel your driver should use the
> extcon framework along with phy framework.

Currently USB PHY notifications are not going through the extcon framework. 
struct usb_phy includes its own notify_connect/notify_disconnect callbacks 
(see include/linux/usb/phy.h). Do you think USB should use extcon instead? USB 
PHY notifies carry the USB interface speed information, while extcon notifies 
seems to only carry boolean cable state.

> Adding extcon support in the generic PHY framework is something I have not
> thought through in detail.

Thanks,
baruch

> > diff --git a/drivers/usb/chipidea/ci_hdrc_usb2.c 
> > b/drivers/usb/chipidea/ci_hdrc_usb2.c
> > index 45844c951788..cc3aeb781a57 100644
> > --- a/drivers/usb/chipidea/ci_hdrc_usb2.c
> > +++ b/drivers/usb/chipidea/ci_hdrc_usb2.c
> > @@ -35,11 +35,16 @@ static int ci_hdrc_usb2_probe(struct platform_device *pdev)
> >  	struct device *dev = &pdev->dev;
> >  	struct ci_hdrc_usb2_priv *priv;
> >  	struct ci_hdrc_platform_data *ci_pdata = dev_get_platdata(dev);
> > +	struct usb_phy *usb_phy;
> >  	int ret;
> >  
> >  	if (!ci_pdata)
> >  		ci_pdata = &ci_default_pdata;
> >  
> > +	usb_phy = devm_usb_get_phy_by_phandle(&pdev->dev, "usb-phy", 0);
> > +	if (!IS_ERR(usb_phy))
> > +		ci_pdata->usb_phy = usb_phy;
> > +
> >  	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> >  	if (!priv)
> >  		return -ENOMEM;
> > 

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