linux-kernel - Re: [PATCH v3 07/11] usb: otg: add OTG core

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Date:	Mon, 20 Jul 2015 09:45:01 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Roger Quadros <rogerq@...com>
CC:	Li Jun <b47624@...escale.com>, <stern@...land.harvard.edu>,
	<balbi@...com>, <gregkh@...uxfoundation.org>,
	<dan.j.williams@...el.com>, <jun.li@...escale.com>,
	<mathias.nyman@...ux.intel.com>, <tony@...mide.com>,
	<Joao.Pinto@...opsys.com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v3 07/11] usb: otg: add OTG core

On Fri, Jul 17, 2015 at 03:06:18PM +0300, Roger Quadros wrote:
> >> +
> >> +/**
> >> + * OTG FSM ops function to start/stop host
> >> + */
> >> +static int usb_otg_start_host(struct otg_fsm *fsm, int on)
> >> +{
> >> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> >> +	struct otg_hcd_ops *hcd_ops;
> >> +
> >> +	dev_dbg(otgd->dev, "otg: %s %d\n", __func__, on);
> >> +	if (!fsm->otg->host) {
> >> +		WARN_ONCE(1, "otg: fsm running without host\n");
> >> +		return 0;
> >> +	}
> >> +
> >> +	if (on) {
> >> +		/* OTG device operations */
> >> +		if (otgd->start_host)
> >> +			otgd->start_host(fsm, on);
> >> +
> >> +		/* start host */
> >> +		hcd_ops = otgd->primary_hcd.ops;
> >> +		hcd_ops->add(otgd->primary_hcd.hcd, otgd->primary_hcd.irqnum,
> >> +			     otgd->primary_hcd.irqflags);
> >> +		if (otgd->shared_hcd.hcd) {
> >> +			hcd_ops = otgd->shared_hcd.ops;
> >> +			hcd_ops->add(otgd->shared_hcd.hcd,
> >> +				     otgd->shared_hcd.irqnum,
> >> +				     otgd->shared_hcd.irqflags);
> >> +		}
> >> +	} else {
> >> +		/* stop host */
> >> +		if (otgd->shared_hcd.hcd) {
> >> +			hcd_ops = otgd->shared_hcd.ops;
> >> +			hcd_ops->remove(otgd->shared_hcd.hcd);
> >> +		}
> >> +		hcd_ops = otgd->primary_hcd.ops;
> >> +		hcd_ops->remove(otgd->primary_hcd.hcd);
> >> +
> >> +		/* OTG device operations */
> >> +		if (otgd->start_host)
> >> +			otgd->start_host(fsm, on);
> >> +	}
> >> +
> >> +	return 0;
> >> +}
> > 
> > I do not see much benefit by this override function, usb_add/remove_hcd
> > can be simply included by controller's start_host function, also there
> > maybe some additional operations after usb_add_hcd, but this override
> > function limit usb_add_hcd() is the last step.
> 
> I had tried host start/stop way before but Alan's suggestion was to use
> bind/unbind the host controller completely as that is much simpler
> 
> [1] http://article.gmane.org/gmane.linux.usb.general/123842
> 

Jun may want we have some ways to override otg_fsm->ops by platform
drivers, I think we all agree to call usb_add_hcd/usb_remove_hcd
to start/stop host roles, just some platforms may need more than
just call them.

-- 

Best Regards,
Peter Chen
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