linux-kernel - Re: [PATCH v2] USB: ehci-s5p: Fix phy reset

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Message-Id: <0A9719D9-5957-44B8-8466-F0F454588B2C@suse.de>
Date:	Thu, 14 Mar 2013 13:04:00 +0100
From:	Alexander Graf <agraf@...e.de>
To:	Doug Anderson <dianders@...omium.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-usb@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	dmueller@...e.de, Vivek Gautam <gautam.vivek@...sung.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] USB: ehci-s5p: Fix phy reset


On 14.03.2013, at 04:38, Doug Anderson wrote:

> Alexander,
> 
> On Wed, Mar 13, 2013 at 4:59 PM, Alexander Graf <agraf@...e.de> wrote:
>> On my Exynos 5 based Arndale system, I need to pull the reset line down
>> and then let it go up again to actually perform a reset. Without that
>> reset, I can't find any USB hubs on my bus, rendering the USB controller
>> useless.
>> 
>> We also only need to reset the line after the phy node has been found.
>> This way we don't accidently reserve the vbus GPIO pin, but later on
>> defer the creation of our controller, because the phy device tree node
>> hasn't been probed yet.
>> 
>> This patch implements the above logic, making EHCI and OHCI work on
>> Arndale systems for me.
>> 
>> Signed-off-by: Alexander Graf <agraf@...e.de>
>> CC: Vivek Gautam <gautam.vivek@...sung.com>
>> CC: Jingoo Han <jg1.han@...sung.com>
>> CC: Alan Stern <stern@...land.harvard.edu>
>> CC: Kukjin Kim <kgene.kim@...sung.com>
>> CC: Felipe Balbi <balbi@...com>
>> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> CC: Doug Anderson <dianders@...omium.org>
>> 
>> ---
>> 
>> v1 -> v2:
>> 
>>  - remove gpio_free call
>>  - move reset logic after phy node search
> 
> Seems fine to me.  I guess the earlier problem you wrote about was the
> probe failure, then?  

Well, the problem I wrote about was that when I do

  * probe
    -> reset phy
  * probe gets deferred
  * deferred probe
    -> can't reset phy because the pin is already in use

Then I get the same breakage again. However, if I do

  * probe
  * probe gets deferred
  * deferred probe
    -> reset phy

Then everything works just fine.

> I think that the reason I don't tend to get the
> probe failure is that I've got my device tree ordered differently so
> that the phy gets initted in a different order.

Odd - I get the deferral regardless of how I order my device tree :).


Alex

> 
> I'll send up the devm_ patch atop this.
> 
> Reviewed-by: Doug Anderson <dianders@...omium.org>
> 
> Thanks!  :)
> 
> -Doug

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