Message-ID: <54E948AC.2010609@linaro.org>
Date:	Sun, 22 Feb 2015 11:10:36 +0800
From:	zhangfei <zhangfei.gao@...aro.org>
To:	balbi@...com
CC:	Kishon Vijay Abraham I <kishon@...com>, mark.rutland@....com,
	Peter Chen <peter.chen@...escale.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"dan . zhao" <dan.zhao@...ilicon.com>,
	Wangbinghui <wangbinghui@...ilicon.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v4 4/4] phy: add phy-hi6220-usb

Hi, Balbi

On 02/22/2015 12:21 AM, Felipe Balbi wrote:
> Hi,
>
> On Sat, Feb 21, 2015 at 11:03:05PM +0800, zhangfei 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.
>
> no problem.
>
>> 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
>
> drivers/phy, if the framework misses anything you need, it's a great
> opportunity to give back to the community by extending the framework.

Sorry, I am a little confused.
I need some concrete suggestion for the next step of this patch, which 
is required for the community board, hikey board.

Do you mean in the future we need use hsotg->phy instead of hsotg->uphy.
         struct phy *phy;
         struct usb_phy *uphy;
usb_phy has many members that struct phy does not have, including otg.
struct usb_otg          *otg;
Is that mean we need port such member from usb_phy to phy.

Besides, are you ok with using usb_gadget_vbus_connect/disconnect.

>
> Scratching one's own itch kinda thing...
>
>>>>>> +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.
>
> well, add DT. The whole idea of free software is that we improve on
> things we already have. EXTCON is *the* API to handle such things.

I think I am still not understanding extcon-gpio, not sure why need use 
this API here.

Here two gpio requires, one gpio as interrupt, in the interrupt handler, 
we detect the gpio status judging the otg status.
extcon-gpio.c use the interrupt, then can we also use the gpio interrupt.
Using extcon-gpio is used for saving gpio_request?

>
> Quite frankly, though, Roger Quadros (now in Cc) has been working to get
> DT support on extcon-gpio, so perhaps wait for that and base your
> patches on top of his.
>
> Now your statement that GPIO is clear enough is completely bogus to me.
>
> Why do we have fixed regulators with GPIO enable signals, right ? Might
> as well just fiddle with the GPIO directly, right ? Wrong, the idea of
> using these frameworks is to encapsulate implementation details and make
> sure that if things change from one board to another, we can still use
> our SW without major modifications.
>
>>>>>> +	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.
>
> then the framework should implement it in SW. That was the whole idea of
> adding set_debounce() to gpiolib. If the controller can't handle it,
> gpiolib handles it in SW. Again, encapsulating details.
>
>>>> 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.
>
> debounce might be very well needed. We *do* want to filter out the
> transient period. I'm just telling you there are better ways of doing
> so; and your response to that is "let's just remove it" and I'm not
> really comfortable with that attitude.
>
> That's the attitude of a lazy person which, I hope, you are not ;)

Understand.
What I mean here is gpio_id is not used when unplug, it is only used 
after plug.

Thanks
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