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

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Date:	Tue, 18 Jun 2013 11:34:08 +0300
From:	Roger Quadros <rogerq@...com>
To:	<balbi@...com>
CC:	Chao Xie <chao.xie@...vell.com>, <gregkh@...uxfoundation.org>,
	<stern@...land.harvard.edu>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <xiechao.mail@...il.com>
Subject: Re: [PATCH] USB: initialize or shutdown PHY when add or remove host
 controller

On 06/18/2013 11:24 AM, Felipe Balbi wrote:
> HI,
> 
> On Tue, Jun 18, 2013 at 11:23:59AM +0300, Roger Quadros wrote:
>> On 06/18/2013 11:01 AM, Felipe Balbi wrote:
>>> Hi,
>>>
>>> On Tue, Jun 18, 2013 at 03:15:01AM -0400, Chao Xie wrote:
>>>> Some controller need software to initialize PHY before add
>>>> host controller, and shut down PHY after remove host controller.
>>>> Add the generic code for these controllers so they do not need
>>>> do it in its own host controller driver.
>>>>
>>>> Signed-off-by: Chao Xie <chao.xie@...vell.com>
>>>> ---
>>>>  drivers/usb/core/hcd.c |   19 ++++++++++++++++++-
>>>>  1 files changed, 18 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>>>> index d53547d..b26196b 100644
>>>> --- a/drivers/usb/core/hcd.c
>>>> +++ b/drivers/usb/core/hcd.c
>>>> @@ -43,6 +43,7 @@
>>>>  
>>>>  #include <linux/usb.h>
>>>>  #include <linux/usb/hcd.h>
>>>> +#include <linux/usb/phy.h>
>>>>  
>>>>  #include "usb.h"
>>>>  
>>>> @@ -2531,12 +2532,22 @@ int usb_add_hcd(struct usb_hcd *hcd,
>>>>  	 */
>>>>  	set_bit(HCD_FLAG_RH_RUNNING, &hcd->flags);
>>>>  
>>>> +	/* Initialize the PHY before other hardware operation. */
>>>> +	if (hcd->phy) {
>>>
>>> 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.

cheers,
-roger
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