[PATCH 2/2] ARM: dts: Qualcomm APQ8060 DragonBoard ALS sensor

[Linus Walleij]

On Thu, Feb 9, 2017 at 2:42 AM, Bjorn Andersson
<bjorn.andersson at linaro.org> wrote:

>> The AMUX is just one big mystery to me, it's one of those areas where I
>> think a real datasheet would be extremely helpful.
>>
>
> After additional research and a long chat with Stephen this is what I
> have come up with.
>
> On PM8058 you have 16 AMUX channels that can be either read as raw,
> scaled or dived by 3, this is selected by the 2 "premux" bits in the
> AMUX selector register.
>
> AMUX channel 5-9 are called MPP5-9,
> connected to a switching matrix so each MPP is configured to output its
> signal on one of the 5 mpp-amux-channels. I.e. it's probably better to
> rename these just "AMUX5" through "AMXU9".

Awesome, that part is encoded into the next iteration of the driver.

> On PM8921 this changes somewhat and an additional mux is introduced.
> The first premux looks similar to pm8058, but with no direct MPP AMUXes
> to be selected. Premux 1 or 2 is used to select the second level mux.
>
> This mux has channels:
>  1: usb_sns
>  2: dcin_sns
>  3: amux3 (reserved and called pa_therm)
>  4: amux4 (reserved and called amux_in)
>  5-8: amuxX (as configured output of MPPs)
>
> Premux 2 has the same set of channels, but with a divisor of 3.
>
> The MPP1/MPP2 AMUX channels in premux 0 found downstream are now
> reserved - likely they the hardware used to select unity and div/3 input
> from the second level mux.

That is some serious silicon duct tape work going on here...

OK I am trying to accomodate it, but I will likely need verification on
real hardware making use of the premuxed thingies.

Yours,
Linus Walleij