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

Tomasz Figa t.figa at samsung.com
Fri May 16 03:50:40 PDT 2014

On 16.05.2014 12:35, Rahul Sharma wrote:
> On 16 May 2014 15:12, Rahul Sharma <rahul.sharma at samsung.com> wrote:
>> On 16 May 2014 03:14, Tomasz Figa <tomasz.figa at gmail.com> wrote:
>>> On 15.05.2014 06:01, Rahul Sharma wrote:
> [snip]
>>>>> the PHY provider.
>>>> Please correct me if I got you wrong. You want somthing like this:
>>>> pmu_system_controller: system-controller at 10040000 {
>>>>          ...
>>>>           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 at 10040000 {
>>>         /* ... */
>>>         #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.
> Hi Tomasz,
> These PHYs are not part of PMU as such. I am not sure if it is correct to
> probe them as phy provider for all these phys. Only relation of these phys with
> the PMU is 'enable/disable control'.

Well, in reality what is implemented by this driver is not even a PHY,
just some kind of power controllers, which are contained entirely in the

> Controlling this bit using regmap interface
> still looks better to me.

Well, when there is a choice between using regmap and not using regmap,
I'd rather choose the latter. Why would you want to introduce additional
abstraction layer if there is no need for such?

> IMHO Ideal method would be probing these PHYs independently and resolving
> the necessary dependencies like syscon handle, clocks etc. This way we will
> not be having any common phy provider for all these independent PHYs and it
> would be clean to add each of these phy nodes in DT. Please see my original
> comment below.
> http://lkml.iu.edu/hypermail/linux/kernel/1404.1/00701.html

With the solution I proposed, you don't need any kind of dependencies
for those simple power controllers. They are just single bits that don't
need anything special to operate, except PMU clock running.

Best regards,

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