linux-kernel - Re: [PATCH v3] phy: Add new Exynos5 USB 3.0 PHY driver

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Date:	Mon, 17 Feb 2014 15:31:41 +0530
From:	Vivek Gautam <gautamvivek1987@...il.com>
To:	Tomasz Figa <t.figa@...sung.com>
Cc:	Vivek Gautam <gautam.vivek@...sung.com>,
	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>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-doc@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Felipe Balbi <balbi@...com>, kishon <kishon@...com>,
	Kamil Debski <k.debski@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Julius Werner <jwerner@...omium.org>,
	Jingoo Han <jg1.han@...sung.com>
Subject: Re: [PATCH v3] phy: Add new Exynos5 USB 3.0 PHY driver

Hi Tomasz,


On Fri, Feb 14, 2014 at 9:17 PM, Tomasz Figa <t.figa@...sung.com> wrote:

mistakenly didn't do "Reply All", so sending it again.

> Hi Vivek,
>
>
> On 14.02.2014 14:53, Vivek Gautam wrote:
>>>>
>>>> Changes from v2:
>>>> 1) Added support for multiple PHYs (UTMI+ and PIPE3) and
>>>>      related changes in the driver structuring.
>>>
>>>
>>>
>>> I'm a bit skeptical about this separation. Can the PHY operate with just
>>> the
>>> UTMI+ or PIPE3 part enabled alone without the other? Can any PHY consumer
>>> operate this way?
>>
>>
>> Yes :-)
>> As also pointed by Kishon the PHY consumer (which is DWC3 in case of
>> Exynos5 SoC series)
>> should theoretically be able use either UTMI+ phy for High speed
>> operations or both (UTMI+ and PIPE3)
>> for Super Speed operations.
>
>
> OK, that's fine then. This is the explanation I needed, thanks.
>
>
>>>
>>> I believe the right thing to do here is to do all the initialization in
>>> .power_on() and let the driver simply call phy_power_on() when it needs
>>> the
>>> PHY and phy_power_off() otherwise.
>>
>>
>> If this is what we should be doing then what will be the purpose of
>> two separate APIs :
>> phy_power_on() and phy_init().
>> Am i missing while understanding the things.
>>
>
> I don't understand this separation as well. Operations that should be done
> together shouldn't be separated. Is there any case when you can call one of
> phy_power_on() and phy_init() without calling another one right before/after
> it?

Most of the PHY consumers need to call phy_power_on() as well as phy_init()
to get PHY working (if the PHY provider gives callback to both).
I think the idea would have been to separate out the initialization
related and power related
jobs (which may include setting up the PMUs and may be regulators ?)
But, i think it's true, if the PHY provider callback for both
phy_power_on() and phy_init()
then the consumer __has__ to call both to get things working.



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