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

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Date:	Fri, 14 Feb 2014 16:47:29 +0100
From:	Tomasz Figa <t.figa@...sung.com>
To:	Vivek Gautam <gautamvivek1987@...il.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 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?

Best regards,
Tomasz
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