The meson-saradc allows switching the input of channel #6 between an actual ADC pad and the SoC's internal temperature sensor. On the 64-bit SoCs the SCPI firmware reads the chip temperature using the SAR ADC. Thus the 64-bit SoCs simply expose the temperature through the "arm,scpi-sensors" interface (and so Linux doesn't have to program the SAR ADC for temperature readings). The 32-bit SoCs however don't have any SCPI firmware. Thus we need to configure the SAR ADC in Linux to get the chip temperature. To make it work we need two changes to the existing dt-bindings: - we have to get the TSC (temperature sensor calibration coefficient) from the eFuse (where it has been programmed to the correct value in the manufacturing process). the SAR ADC needs the TSC value, otherwise it returns only garbage readings - we need to get a phandle to the new HHI syscon region because on Meson8b and Meson8m2 the TSC is five bits wide (on Meson8 it's only four bits wide) but only four bits are stored inside the SAR ADC's memory region. The upper most bit (not all five bits, only one out of five) is stored at a seemingly random register HHI_DPLL_TOP_0) in the HHI register area. Dependencies: The SAR ADC changes are completely independent from anything else. However, the arch/arm/boot/dts changes from this series depend on my other series "Meson8/Meson8b: introduce a HHI syscon node" from [0]. I decided to send them all together to give a better overview how the end result looks like - I can split the dts changes into a separate series when requested (in any case I would like Kevin to take them through his linux-amlogic tree). [0] https://patchwork.kernel.org/cover/10658527/ Martin Blumenstingl (7): dt-bindings: iio: adc: meson-saradc: add temperature sensor support iio: adc: meson-saradc: add support for the chip's temperature sensor ARM: dts: meson8: add the temperature calibration data for the SAR ADC ARM: dts: meson8b: add the temperature calibration data for the SAR ADC ARM: dts: meson8b: ec100: add iio-hwmon for the chip temperature ARM: dts: meson8b: odroidc1: add iio-hwmon for the chip temperature ARM: dts: meson8m2: mxiii-plus: add iio-hwmon for the chip temperature .../bindings/iio/adc/amlogic,meson-saradc.txt | 10 + arch/arm/boot/dts/meson8.dtsi | 8 + arch/arm/boot/dts/meson8b-ec100.dts | 5 + arch/arm/boot/dts/meson8b-odroidc1.dts | 5 + arch/arm/boot/dts/meson8b.dtsi | 8 + arch/arm/boot/dts/meson8m2-mxiii-plus.dts | 5 + drivers/iio/adc/meson_saradc.c | 274 ++++++++++++++++-- 7 files changed, 289 insertions(+), 26 deletions(-) -- 2.19.1
