[PATCH 2/2] realtek: add support for HPE 1920-24G-PoE-370w

[Evan Jobling]

Hi Tim!> 
> My thoughts were that the kernel's gpio-init code for that SoC shouldn't reset the gpio state - rather it should leave it in the state that the firmware configured it.  gpio-fan would then do the right thing.

I've read the RTL8231 device driver and  code sets everything to input
to ensure output drivers are always in a valid state.

Commit is 3810e897295cb66bc45a62bc2c0b70a01004fe3b

"realtek: ensure output drivers are enabled in RTL8231"

I guess this is going to require per device patching to restore the
fan (and other?) GPIO state set by the bootloader when initialising RTL8231's?

Still working on it.

> 
> I think the only really "correct" ways to proceed are either to allow user control (defaulting to high speed i.e. delegating the decision), or to re-implement the same fan control algorithm as the OEM firmware does.
> 
> That algorithm could probably be discovered by treating it as a black box (e.g. giving it different PoE power loads, and/or operating temperatures, simulating fan failures etc. and observing behaviour)
> 
> Unfortunately I think that without access to the hardware specs and/or carrying out a lot of hardware characterisation work there is too much guesswork involved in implementing any other algorithm.
I think my laziness will prevail and I'll end up cooking up my own script rather than doing the reverse engineering work haha.

Hotbox and loading up with PoE to near max on JG926A isn't out of the realm of possibility.
Don't really want to try to run equipment at 40C ambient but I guess that's summer here anyway.
Won't be able to get higher than 80W PoE draw on the JG922A with my current equipment.

Cheers,
Evan.