[PATCH v2 0/5] Battery temperature ADC plumbing on Qualcomm platforms

[Luca Weiss]

This implements a solution to get battery temperature readings working
on (for example) smartphones with Qualcomm SoCs.

The solution chosen in downstream Qualcomm kernels is exposing
ADC_BAT_THERM_PU* in the ADC driver as temperature channels with the
lookup table ("struct vadc_map_pt") for the specific NTC found in a
device's battery patched to adjust the lookup table. Patching a kernel
per-device is obviously nothing we can put upstream.

The high level solution proposed here:
* ADC driver provides temperature channel in (milli)volt as IIO channel
* generic-adc-thermal driver converts voltage to temperature based on
  provided lookup table from DT (driver has one IIO channel input, one
  IIO channel output)
* The fuel gauge driver can use that temperature IIO channel to expose
  battery temperature via the power supply device

See RFC for other variants or alternatives considered.

Signed-off-by: Luca Weiss <luca.weiss@xxxxxxxxxxxxx>
---
Changes in v2:
- Rebase on linux-next (a different patch to add IIO to
  generic-adc-thermal has already landed upstream)
- Un-mark as RFC
- Link to v1: https://lore.kernel.org/r/20251010-bat-temp-adc-v1-0-d51ec895dac6@xxxxxxxxxxxxx

---
Luca Weiss (5):
      iio: adc: qcom-spmi-adc5: Add battery thermal channels
      dt-bindings: thermal: generic-adc: Document #io-channel-cells
      thermal/drivers/generic-adc: Allow probe without TZ registration
      arm64: dts: qcom: pm7250b: Define battery temperature ADC channels
      arm64: dts: qcom: sm7225-fairphone-fp4: Add battery temperature node

 .../bindings/thermal/generic-adc-thermal.yaml      |  4 ++
 arch/arm64/boot/dts/qcom/pm7250b.dtsi              | 24 +++++++
 arch/arm64/boot/dts/qcom/sm7225-fairphone-fp4.dts  | 83 ++++++++++++++++++++++
 drivers/iio/adc/qcom-spmi-adc5.c                   |  6 ++
 drivers/iio/adc/qcom-vadc-common.c                 | 16 +++++
 drivers/thermal/thermal-generic-adc.c              | 20 +++---
 include/linux/iio/adc/qcom-vadc-common.h           |  3 +
 7 files changed, 147 insertions(+), 9 deletions(-)
---
base-commit: 8dd3bcb7855ad929d732f48e8a2307fdab6a5667
change-id: 20251010-bat-temp-adc-8539bf0b85bc

Best regards,
-- 
Luca Weiss <luca.weiss@xxxxxxxxxxxxx>