linux-kernel - Re: [PATCH v3 1/3] phy: Add exynos-simple-phy driver

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Date:	Thu, 15 May 2014 23:44:07 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Rahul Sharma <rahul.sharma@...sung.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Tomasz Stanislawski <t.stanislaws@...sung.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	sunil joshi <joshi@...sung.com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Andrzej Hajda <a.hajda@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
	PANKAJ KUMAR DUBEY <pankaj.dubey@...sung.com>
Subject: Re: [PATCH v3 1/3] phy: Add exynos-simple-phy driver

On 15.05.2014 06:01, Rahul Sharma wrote:
> Thanks Tomasz,
> 
> On 15 May 2014 01:31, Tomasz Figa <tomasz.figa@...il.com> wrote:
>> Hi Rahul, Tomasz,
> [snip]
>>> +     simplephys: simple-phys@...40000 {
>>> +             compatible = "samsung,exynos5250-simple-phy";
>>
>> Missing reg property or unnecessary @unit-address suffix in node name.
> 
> I should have removed "@unit-address". I will change this.
> 
>>
>>> +             samsung,pmu-syscon = <&pmu_system_controller>;
>>> +             #phy-cells = <1>;
>>> +     };
>>
>> In general, the idea is quite good, but I think this should rather bind
>> to the main PMU node, since this is just a part of the PMU, not another
>> device in the system. This also means that the PMU node itself should be
>> the PHY provider.
>>
> 
> Please correct me if I got you wrong. You want somthing like this:
> 
> pmu_system_controller: system-controller@...40000 {
>          ...
>           simple_phys: simple-phys {
>                         compatible = "samsung,exynos5420-simple-phy";
>                         ...
>           };
> };

Not exactly.

What I meant is that the PMU node itself should be the PHY provider, e.g.

pmu_system_controller: system-controller@...40000 {
	/* ... */
	#phy-cells = <1>;
};

and then the PMU node should instantiate the Exynos simple PHY driver,
as this is a driver for a facility existing entirely inside of the PMU.
Moreover, the driver should be rather called Exynos PMU PHY.

I know this isn't really possible at the moment, but with device tree we
must design things carefully, so it's better to take a bit more time and
do things properly.

So my opinion on this is that there should be a central Exynos PMU
driver that claims the IO region and instantiates necessary subdrivers,
such as Exynos PMU PHY driver, Exynos CLKOUT driver, Exynos cpuidle
driver and more, similar to what is being done in drivers/mfd.

Now, there is already ongoing effort to convert current freestanding PMU
configuration code in mach-exynos into a full-fledged PMU driver, but
not exactly in the same direction as I stated above. I'll try to
cooperate with Pankaj, who is responsible for this work to make this go
into the right track.

Best regards,
Tomasz
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