Re: [PATCH v4 4/4] phy: add phy-hi6220-usb

[zhangfei]

Hi, Balbi

On 02/21/2015 12:06 AM, Felipe Balbi wrote:
> Hi,
>
> On Fri, Feb 20, 2015 at 11:44:37PM +0800, zhangfei wrote:
> > Hi, Balbi
> >
> > On 02/20/2015 10:41 PM, Felipe Balbi wrote:
> >
> > > > +static void hi6220_start_peripheral(struct hi6220_priv *priv, bool on)
> > > > +{
> > > > +	struct usb_otg *otg = priv->phy.otg;
> > > > +
> > > > +	if (!otg->gadget)
> > > > +		return;
> > > > +
> > > > +	if (on)
> > > > +		usb_gadget_connect(otg->gadget);
> > > > +	else
> > > > +		usb_gadget_disconnect(otg->gadget);
> > >
> > > why is the PHY fiddling with pullups ?
> >
> > We use this to enable/disable otg gadget mode.
>
> I got that, but the pullups don't belong to the PHY, they belong to the
> gadget.
>
> > The gpio_id & gpio_vbus are used to distinguish otg gadget mode or
> > host mode.
> > When micro usb or otg device attached to otg, gpio_vbus falling down.
> > And gpio_id = 1 is micro usb, gpio_id = 0 is otg device.
>
> all of that I understood clearly :-)
>
> > So when micro usb attached, we enable gadget mode; while micro usb
> > detached, we disable gadget mode, and dwc2 will automatically set to
> > host mode.
>
> that's all fine, I'm concerned about letting the PHY fiddle with
> something it doesn't own. If I am to change pullups rules in udc-core,
> this is likely to break down miserably and I don't want to have to go
> through that.

Thanks for the clarifying.

How about using usb_gadget_vbus_connect/disconnect, which are used in 
many files under drivers/usb/phy.
There is no vbus_session in dwc2/gadget.c, I thought it would be same as 
pullup.

However, usb_gadget_vbus_connect still need para gadget, where should we 
put this file, drivers/usb/phy or drivers/phy

> > > > +static void hi6220_detect_work(struct work_struct *work)
> > > > +{
> > > > +	struct hi6220_priv *priv =
> > > > +		container_of(work, struct hi6220_priv, work.work);
> > > > +	int gpio_id, gpio_vbus;
> > > > +	enum usb_otg_state state;
> > > > +
> > > > +	if (!gpio_is_valid(priv->gpio_id) || !gpio_is_valid(priv->gpio_vbus))
> > > > +		return;
> > > > +
> > > > +	gpio_id = gpio_get_value_cansleep(priv->gpio_id);
> > > > +	gpio_vbus = gpio_get_value_cansleep(priv->gpio_vbus);
> > >
> > > looks like this should be using extcon
> > Not used extcon before.
> > However, we need gpio_vbus interrupt.
> > Checked phy-tahvo.c and phy-omap-otg.c, not find extcon related with
> > interrupt.
> > Will investigate tomorrow.
>
> drivers/extcon/extcon-gpio.c
I think there is no need to use extcon, gpio is clear enough.
extcon-gpio.c even do not support dt.

> > > > +	if (gpio_vbus == 0) {
> > > > +		if (gpio_id == 1)
> > > > +			state = OTG_STATE_B_PERIPHERAL;
> > > > +		else
> > > > +			state = OTG_STATE_A_HOST;
> > > > +	} else {
> > > > +		state = OTG_STATE_A_HOST;
> > > > +	}
> > > > +
> > > > +	if (priv->state != state) {
> > > > +		hi6220_start_peripheral(priv, state == OTG_STATE_B_PERIPHERAL);
> > > > +		priv->state = state;
> > > > +	}
> > > > +}
> > > > +
> > > > +static irqreturn_t hiusb_gpio_intr(int irq, void *data)
> > > > +{
> > > > +	struct hi6220_priv *priv = (struct hi6220_priv *)data;
> > > > +
> > > > +	/* add debounce time */
> > > > +	schedule_delayed_work(&priv->work, msecs_to_jiffies(100));
> > >
> > > this is really bad. We have threaded interrupt support, right ?
> >
> > Since we use two gpio to distinguish gadget mode or host mode.
> > Debounce time can introduce more accuracy.
>
> gpio_set_debounce() ?
Not all gpio.c support set_debounce, including gpio-pl061.c.

> > I think threaded interrupt can not be used for adding debounce time.
> > Here add debounce is just for safety.
>
> add the debounce to the gpio itself.

Here the debounce added only for safety.
gpio_id may mis-report when unplug usb, but it is correct for plug usb & 
otg device.
So debounce can be omitted.
If you think using delayed work for debounce is ugly, it is fine switch 
to threaded_irq.

Thanks

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