Re: exynos4412: porting hdmiddc and hdmiphy node entries

[Tobias Jakobi <liquid.acid@gmx.net>]

Hello Tomasz,

thanks a lot for the support!

> The meaning of hdmiphy is ambiguous.
> In exynos4 spec there are _TWO_ components named HDMIPHY.
> The first one is a PLL that generates a clock for HDMI subsystem.
> This PLL is controlled by I2C.
> 
> You can find an example of its bindings at:
> http://lists.freedesktop.org/archives/dri-devel/2013-October/047687.html
OK, that looks exactly like the bindings I currently have in the dts.


> The second one is HDMI's physical interface located in PMU unit.
> 
> The exynos-simple-phy is dedicated to controller the former (component of PMU).
> 
> The 'phy' attribute in DT refers to the PLL.
> There is a debate if 'phy' should refer to I2C device itself or
> rather to I2C bus. Currently it refers to driverless instance
> of I2C device.
By 'driverless' you mean that the node isn't probed by any specific
driver code / the 'compatible' string isn't used anywhere in the kernel
(like it's currently the situation?)


>> Somehow this doesn't look right. And indeed:
>> https://patchwork.kernel.org/patch/4021121/
>>
>> At least for exynos5250 this node is not a child on an i2c adapter.
> 
> This is a completely different HDMIPHY.
I'm not sure I understand. Different from the PPL and the PMU HDMIPHY?


>> And yes, I would still have to add 'phys' and 'phy-names' to the hdmi
>> node. This looks wrong again. Why do I have to specify 'phys' when I
>> already have 'phy' there? Isn't that redundant?
> 
> 'phys' and 'phy-names' refers to PHY interfaces delivered by phy-core.
> The attribute named 'phy' refers to I2C device used to controller HDMI's PLL.
> The naming convention is very misleading.
Hmm, indeed this is very confusing. So with the move to
exynos-simple-phy, I guess I need these entries as well, am I correct?


>> Well, you see, lots of confusion here. I would appreciate any kind of
>> help on how to proceed here.
> 
> The documentation for HDMI's bindings should be fixed.
Well, I can agree with that :)


With best wishes,
Tobias