[Galaxy S III Accessories] Diim:
First of all, something strikes me.

If I understand correctly, the adapter you have built has power supplies of the MHL adapter and the one of the USB OTG output connected together. So, I can see the following cases:

1) When the MHL adapter is NOT connected:

You are in a normal USB OTG output configuration, (what is detected by the pull down resistor on your sense cable pin), and everything should work normally with the USB hub. You should be able to see the 5V power supply on the 5pin female MHL port.

=> Do you confirm that ?

Note: Since your USB HUB is power supplied only by the phone, each of your hub output port could only be in Low Power mode, meaning with output current limited to 100mA. (A normal USB HUB would suspend the port if the connected peripheral requests more than 100mA).

2a) When you connect the MHL adaptater, but WITHOUT connecting the wall charger:

Since the phone detects the pull-down resistor on the USB connector sense pin, the phone provides 5V power supply (limited to 500mA or 100mA depending on what the HUB requests in the negotiation phase).

As a result, the MHL adapter should be power supplied as well (if there is no added electronic mechanism in it that check whether the power comes from the wall charger or the upstream MHL connector), and the HDMI output should work (provided that the required current by the adapter does not exceed the allowed current by the phone)

=> Do you confirm ?

As for USB HUB, it should work with all ports limited to 100mA.

2b) When you connect the MHL adapter, with wall charger connected:

As for USB HUB, it should work with all ports limited to 100mA (same as 1) and 2a) )

As for MHL adapter, since powered by wall charger (as intended to), HDMI output should work properly.

HOWEVER: One of the key feature of the MHL standards is to let the Display device (like a TV) charge the phone (in our case, since the MHL adapter is a MHL to HDMI bridge intended to NOT MHL-Enabled display devices, the power supplies comes from the wall charger instead).

SO THERE MAY BE A POWER SUPPLY CONFLICT between the 5V power supplied from the phone and the 5V power supplied from the MHL adapter.​

To sum it up:

Case 1) USB hub must work properly

Case 2a) USB hub must work properly. HDMI output MAY work out.

Case 2b) USB hub must work properly. HDMI output must work properly. Howerver, there should be a power supply conflict in this case.

In all cases, the USB HUB shouldn't be able to supply more than 100mA on each port.​

Additional important note, regarding the smart dock:

Case 1) and 2a) are NOT SUPPORTED by smart dock. The embedded hub and the HDMI output do only work when smart dock is power supplied by wall charger. And the phone does not even detect the smart dock.

Case 2b) is of course supported by smart dock. I do not know how the smart dock manages the power supply conflict right now. But since the hub is powered supplied directly by the wall charger, each of the output ports should be able to provide up to 500mA.

EDIT: I do not know if that matters, but I tried that with my GN2, stock ROM JB 4.1.2

Here are some useful application notes from maxim, related to these topic:

USB OTG: http://www.maximintegrated.com/app-notes/index.mvp/id/1822

USB battery charging: http://www.maximintegrated.com/app-notes/index.mvp/id/4803

Will try to find time to open my smart dock and have a closer look of what is in there.