linux-kernel - Re: [PATCH] USB: initialize or shutdown PHY when add or remove host controller

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Message-ID: <CADApbeiT+zv9kkrJ+J3XMZ1WWBXeHaQ20u12V2+DbOs3mB6vzA@mail.gmail.com>
Date:	Tue, 18 Jun 2013 17:27:07 +0800
From:	Chao Xie <xiechao.mail@...il.com>
To:	"balbi@...com" <balbi@...com>
Cc:	Roger Quadros <rogerq@...com>, Chao Xie <chao.xie@...vell.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] USB: initialize or shutdown PHY when add or remove host controller

On Tue, Jun 18, 2013 at 4:48 PM, Felipe Balbi <balbi@...com> wrote:
> Hi,
>
> On Tue, Jun 18, 2013 at 11:45:05AM +0300, Roger Quadros wrote:
>> >>>>> this looks wrong for two reasons:
>> >>>>>
>> >>>>> a) you're not grabbing the PHY here.
>> >>>>>
>> >>>>>         You can't just assume another entity grabbed your PHY for you.
>> >>>>
>> >>>> Isn't that done in the controller drivers e.g. ehci-fsl.c, ohci-omap, etc?
>> >>>
>> >>> right, and what I'm saying is that it should all be re-factored into
>> >>> ehci-hcd core :-)
>> >>>
>> >>>> If the controllers don't want HCD core to manage the PHY they can just set it
>> >>>> to some error code.
>> >>>
>> >>> they shouldn't have the choice, otherwise it'll be a bit of a PITA to
>> >>> maintain the code. ehci core tries to grab the PHY, if it's not there,
>> >>> try to continue anyway. Assume it's not needed.
>> >>>
>> >>
>> >> OK fine, but ehci-omap is a weird case as it needs a slightly different
>> >> sequence as to when PHY is initialized depending on which mode it is. (Transceiver
>> >> or transceiver-less). please see this fix.
>> >> http://www.spinics.net/lists/stable/msg12106.html
>> >>
>> >> All I'm saying as that ehci-omap needs a way to tell hcd core that it needs PHY
>> >> handling for itself.
>> >
>> > why don't you do that always ? Meaning, why don't you *always* take PHY
>> > out of suspend ? If PHY is suspended, you can't wakeup unless you have
>> > (in OMAP case) pad wakeup working, right ?
>> >
>>
>> Maybe I wasn't clear before. This is nothing about wakeup and e always take PHY out of suspend.
>> The problem is when to take it out of suspend relative to when EHCI controller starts.
>> Let me clarify.
>>
>> In Transceiver mode we need this.
>>
>> - bring phy out of reset
>> - start EHCI controller
>>
>> Whereas for Transceiver-less mode we need this.
>>
>> - start EHCI controller
>> - bring phy out of reset
>>
>> If there is some way to signal this behaviour to the HCD core, it
>> should be good enough.
>
> alright, now I get it. That's quite messed up that it has to be this way
> :-p
>
It depends on the host controler's driver ehci-xxx to get the phy and
set it to hcd->phy.
If some controller do not want HCD or EHCI-HCD to do the phy
initialization and shutdown, just do not set hcd->phy, and it will be
NULL.
If the host controller driver successlly get the phy, it can set
hcd->phy, or it need return false in its probe.


> --
> balbi
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