linux-kernel - Re: [PATCH v6 4/4] phy: exynos5-usbdrd: Calibrate LOS levels for exynos5420/5800

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Message-ID: <CAFp+6iErXKpXgE0tRPB=tEqXxcXgQAeFJP1TpSwRN6fNu9a-qw@mail.gmail.com>
Date:	Wed, 10 Sep 2014 13:26:57 +0530
From:	Vivek Gautam <gautam.vivek@...sung.com>
To:	Felipe Balbi <balbi@...com>
Cc:	Julius Werner <jwerner@...gle.com>,
	Julius Werner <jwerner@...omium.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...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>,
	Greg KH <gregkh@...uxfoundation.org>, kishon <kishon@...com>,
	Alan Stern <stern@...land.harvard.edu>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Jingoo Han <jg1.han@...sung.com>
Subject: Re: [PATCH v6 4/4] phy: exynos5-usbdrd: Calibrate LOS levels for exynos5420/5800

On Wed, Sep 10, 2014 at 10:53 AM, Vivek Gautam <gautam.vivek@...sung.com> wrote:
> On Wed, Sep 10, 2014 at 10:23 AM, Felipe Balbi <balbi@...com> wrote:
>> On Wed, Sep 10, 2014 at 09:09:57AM +0530, Vivek Gautam wrote:
>>> On Wed, Sep 10, 2014 at 9:07 AM, Vivek Gautam <gautam.vivek@...sung.com> wrote:
>>> > adding Julius here,
>>>
>>> i think i had missed adding Julius for this entire series :-(
>>> I should be more careful with the CC list in future.
>>> Added his chromium id, since that seems to be more active.
>>>
>>> >
>>> >
>>> > On Tue, Sep 9, 2014 at 8:12 PM, Felipe Balbi <balbi@...com> wrote:
>>> >> On Tue, Sep 09, 2014 at 07:19:50AM +0530, Vivek Gautam wrote:
>>> >>> Hi,
>>> >>>
>>> >>>
>>> >>> On Mon, Sep 8, 2014 at 7:14 PM, Felipe Balbi <balbi@...com> wrote:
>>> >>> > Hi,
>>> >>> >
>>> >>> > On Mon, Sep 08, 2014 at 09:53:09AM +0530, Vivek Gautam wrote:
>>> >>> >> On Fri, Sep 5, 2014 at 11:26 PM, Felipe Balbi <balbi@...com> wrote:
>>> >>> >> > On Thu, Sep 04, 2014 at 12:01:19PM +0530, Vivek Gautam wrote:
>>> >>> >> >> > Don't we have phy_power_on()
>>> >>> >> >> > for that ? It looks like you could just as well do this from
>>> >>> >> >> > phy_power_on() ?
>>> >>> >> >>
>>> >>> >> >> No, unfortunately keeping these calibration settings in phy_power_on()
>>> >>> >> >> doesn't help, since we need to do this after XHCI reset has happened.
>>> >>> >> >
>>> >>> >> > teach xHCI about PHYs ?
>>> >>> >>
>>> >>> >> sorry i couldn't understand you here.
>>> >>> >> Aren't we trying to do the same with Heikki's patch about dwc3 :
>>> >>> >> [PATCH 6/6] usb: dwc3: host: convey the PHYs to xhci
>>> >>> >>
>>> >>> >> and the 2nd patch in this series :
>>> >>> >> [PATCH v6 2/4] usb: host: xhci-plat: Get PHYs for xhci's hcds
>>> >>> >>
>>> >>> >> Is there something else that is expected ?
>>> >>> >
>>> >>> > right, use that to call phy_init() at the right time, then you need to
>>> >>> > add a new ->calibrate() method which, likely, will only be used by you
>>> >>> > ;-)
>>> >>>
>>> >>> so you mean, the xhci should itself call phy_init() at a time suitable,
>>> >>> so that ->calibrate() is not required at all ?

but wait, dwc3 does a phy_init() already, then how xhci will be able to
do that again. We can't do phy_init() multiple times right ?

>>> >>>
>>> >>> i think you meant there - "then you __do not__ need to
>>> >>
>>> >> right :-)
>>> >
>>> > alright, i will prepare a patch for the suggested change.
>>> >
>>> > But AFAI remember we had discussion for this patch in earlier
>>> > version, and Julius suggested to use a generic approach for such
>>> > change wherein other users in future may be able to use the
>>> > facility.
>>
>> right, and what's more generic than adding the support for PHYs straight
>> into xHCI ?
>>
>> What I fear is that we end up opening the doors for every odd
>> platform-specific operation to be added to the framework without really
>> considering what needs to be done. That would defeat the idea of having
>> a generic framework altogether.
>
> Ok, i will prepare the patch series as suggested and post it
> to gather opinion from you. :-)
>
>>
>> cheers
>>
>> --
>> balbi
>
>
>
> --
> Best Regards
> Vivek Gautam
> Samsung R&D Institute, Bangalore
> India



-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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