[PATCH v2 0/4] Amlogic Meson SAR ADC support

[Neil Armstrong]

On 01/15/2017 11:42 PM, Martin Blumenstingl wrote:
> This series add support for the SAR ADC on Amlogic Meson GXBB, GXL and
> GXM SoCs.
> The hardware on GXBB provides 10-bit ADC results, while GXL and GXM are
> providing 12-bit results. Support for older SoCs (Meson8b and Meson8)
> can be added with little effort, most of which is testing I guess (I
> don't have any pre-GXBB hardware so I can't say).
> 
> A new set of clocks had to be added to the GXBB clock controller (used
> by the GXBB/GXL/GXM SoCs) which are required to get the ADC working.
> 
> The ADC itself can sample multiple channels at the same time and allows
> capturing multiple samples (which can be used for filtering/averaging).
> The ADC results are stored inside a FIFO register. More details on what
> the driver supports (or doesn't) can be found in the description of
> patch #3.
> 
> The code is based on the public S805 (Meson8b) and S905 (GXBB)
> datasheets, as well as by reading (various versions of) the vendor
> driver and by inspecting the registers on the vendor kernels of my
> testing-hardware.
> 
> Typical use-cases for the ADC on the Meson GX SoCs are:
> - adc-keys ("ADC attached resistor ladder buttons")
> - SoC temperature measurement (not supported by this driver yet as
>   the system firmware does this already and provides the values via the
>   SCPI protocol)
> - "version-strapping" (different resistor values are used to indicate
>   the board-revision)
> - and of course typical ADC measurements
> 
> Thanks to Heiner Kallweit, Jonathan Cameron and Lars-Peter Clausen for
> reviewing this series and providing valuable input!
> 
> Changes since v1 (all changes are for patch #3, except where noted):
> - fix IRQ number in meson-gx.dtsi (thanks to Heiner Kallweit for
>   providing the correct value), affects patch #4
> - move the most used members of meson_saradc_priv to the beginning
> - remove unused struct member "completion" from meson_saradc_priv
> - use devm_kasprintf() instead of snprintf() + devm_kstrdup()
> - initialize indio_dev->dev.parent earlier in meson_saradc_probe()
> - moved meson_saradc_clear_fifo() logic to a separate function
> - add comment why a do ... while loop is required in
>   meson_saradc_wait_busy_clear()
> - remove SAR_ADC_NUM_CHANNELS and SAR_ADC_VALUE_MASK macros (each of them
>   was only used once and it's an unneeded level of abstraction)
> - fixed multiline comment syntax violations
> - dropped unneeded log messages during initialization
> - set iio_dev name to "meson-gxbb-saradc" or "meson-gxl-saradc"
> - use "indio_dev->dev.parent" in all kernel log calls (dev_warn/err/etc)
>   to make it show the OF node name (instead of the iio device name)
> - introduce struct meson_saradc_data to hold platform-specific
>   information (such as resolution in bits and the iio_dev name)
> 
> 
> Martin Blumenstingl (4):
>   Documentation: dt-bindings: add the Amlogic Meson SAR ADC
>     documentation
>   clk: gxbb: add the SAR ADC clocks and expose them
>   iio: adc: add a driver for the SAR ADC found in Amlogic Meson SoCs
>   ARM64: dts: meson: meson-gx: add the SAR ADC
> 
>  .../bindings/iio/adc/amlogic,meson-saradc.txt      |  31 +
>  arch/arm64/boot/dts/amlogic/meson-gx.dtsi          |   8 +
>  arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi        |  10 +
>  arch/arm64/boot/dts/amlogic/meson-gxl.dtsi         |  10 +
>  drivers/clk/meson/gxbb.c                           |  48 ++
>  drivers/clk/meson/gxbb.h                           |   9 +-
>  drivers/iio/adc/Kconfig                            |  12 +
>  drivers/iio/adc/Makefile                           |   1 +
>  drivers/iio/adc/meson_saradc.c                     | 893 +++++++++++++++++++++
>  include/dt-bindings/clock/gxbb-clkc.h              |   4 +
>  10 files changed, 1023 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt
>  create mode 100644 drivers/iio/adc/meson_saradc.c
> 

Good work martin !

Tested on the P200 board with the resistor ladderred key matrix, patch will be posted shortly.

For all the serie :
Tested-by: Neil Armstrong <narmstrong at baylibre.com>