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

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Message-ID: <20150227020753.GA28634@shlinux2>
Date:	Fri, 27 Feb 2015 10:07:55 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	zhangfei <zhangfei.gao@...aro.org>
CC:	Roger Quadros <rogerq@...com>, <balbi@...com>,
	Kishon Vijay Abraham I <kishon@...com>,
	<mark.rutland@....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

On Thu, Feb 26, 2015 at 04:48:30PM +0800, zhangfei wrote:
> Hi, Roger
> 
> On 02/24/2015 06:13 PM, Roger Quadros wrote:
> >>>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.
> >
> >In my opinion otg structure should belong to the USB core part that takes care
> >of the OTG/DRD state machine. We still don't have a clear solution here and
> >I'm currently investigating this.
> >My current work is to get Dual role functionality working with DWC3 controller and TI
> >platforms.
> >
> >Currently phy drivers take care of OTG operation themselves but there is an opportunity
> >to share code and centralize USB role switching.
> >The USB core should be the owner of the Host controller, Gadget controller and the OTG phy
> >and should take care of the that.
> 
> Good idea.
> If you have any patch, I will be very happy to verify.
> 
> How about adding these things in drivers/phy/phy-core.c, it is also
> sharable, though not in usb core.
> 
> Just tried adding one member struct usb_otg otg to struct phy, since
> not find any good member can hold usb_otg.
> In drivers/phy/phy-core.c, adding extcon_register_interest,
> phy_vbus_notifier, phy_set_peripheral, it works for me, dwc2 on
> hikey board.

Just thinking if we can follow struct usb_hcd and struct ehci_hcd design
way, the generic phy just like hcd, and the usb phy like ehci hcd which
is a private data for hcd. zhangfei, maybe you can have a try.

-- 

Best Regards,
Peter Chen
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