iio: adc: add a driver for Qualcomm PM8xxx HK/XOADC

The Qualcomm PM8xxx PMICs contain a simpler ADC than its
successors (already in the kernel as qcom-spmi-vadc.c):
the HK/XO ADC (Housekeeping/Chrystal oscillator ADC).

As far as I can understand this is equal to the PMICs
using SSBI transport and encompass PM8018, PM8038,
PM8058, and PM8921, so this is shortly named PM8xxx.

This ADC monitors a bunch of on-board voltages and the die
temperature of the PMIC itself, but it can also be routed
to convert a few external MPPs (multi-purpose pins). On
the APQ8060 DragonBoard this feature is used to let this
ADC convert an analog ALS (Ambient Light Sensor) voltage
signal from a Capella CM3605 ALS into a LUX value.

Developed and tested with APQ8060 DragonBoard based on
Ivan's driver and Rama Krishna's patches. The SPMI VADC
driver is quite different, but share enough minor
functionality that I have split out to the common file
in a previous patch.

Cc: [email protected]
Cc: [email protected]
Cc: Ivan T. Ivanov <[email protected]>
Cc: Andy Gross <[email protected]>
Cc: Bjorn Andersson <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Srinivas Kandagatla <[email protected]>
Cc: Rama Krishna Phani A <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>

0 files changed, 0 insertions, 0 deletions