[PATCH v4 00/10] power: supply: max77693: Toggle charging/OTG based on extcon status

[Artur Weber]

This patchset does the following:

- Add CURRENT_MAX and INPUT_CURRENT_MAX power supply properties to
  expose the "fast charge current" (maximum current from charger to
  battery) and "CHGIN input current limit" (maximum current from
  external supply to charger).

- Add functions for toggling charging and OTG modes.

- Add an extcon-based handler that enables charging or OTG depending
  on the cable type plugged in. The extcon device to use for cable
  detection can be specified in the device tree, and is entirely
  optional.

The extcon listener implementation is inspired by the rt5033 charger
driver (commit 8242336dc8a8 ("power: supply: rt5033_charger: Add cable
detection and USB OTG supply")).

Signed-off-by: Artur Weber <aweber.kernel at gmail.com>
---
v3 no longer uses the CHARGER regulator to manage the power status, and
that's for two reasons:

- Regulator enable/disable behavior was interfering with how the power
  supply driver worked (we occasionally got "unbalanced disables"
  errors when switching charging state, despite checking for the
  regulator status with regulator_is_enabled() - the CHARGER reg would
  report as enabled despite the enable count being 0).
  This broke OTG insertion if the OTG cable was plugged in first, and
  sometimes caused warnings on unsuspend.

- Changing the charging values directly in the power supply driver is
  less opaque and lets us avoid bringing in a dependency on regulators.

It also splits the current limits back into two properties:
INPUT_CURRENT_LIMIT and CONSTANT_CHARGE_CURRENT_MAX. Again, there are
two reasons for this split:

- They are two separate current controls, one for USB->charger and one
  for charger->battery, and they have different limits (0-2.1A for CC
  vs 60mA-2.58A for input). Given that the power supply core has the
  properties for both values separately, it's more logical to present
  them as such.

- It's safer to keep these separate; CONSTANT_CHARGE_CURRENT_MAX is
  pretty explicitly only set *once* - at probe time with a safe value
  specified in the DT. This way, INPUT_CURRENT_LIMIT is safer to modify
  since in the event of an invalid value the CC current will hold back
  the extra current thus preventing damage to the battery.

The latter is relevant as I'm working on a follow-up patchset that
allows for controlling the charging parameters using power supply
properties/sysfs properties rather than the CHARGER regulator.

Note that the CHARGER regulator gets disabled automatically if it's
not used, which will disable charging if it was auto-enabled by the
extcon code. This can be worked around by re-attaching the cable, or
more properly by removing the CHARGER regulator from DT for devices
that use the extcon-based charger management, as has been done in the
Galaxy Tab 3 8.0 DTSI.

See v1 for old description:

https://lore.kernel.org/r/20240530-max77693-charger-extcon-v1-0-dc2a9e5bdf30@gmail.com
---
Changes in v4:
- Fix probe deferrals on missing maxim,usb-connector property
- Link to v3: https://lore.kernel.org/r/20240729-max77693-charger-extcon-v3-0-02315a6869d4@gmail.com

Changes in v3:
- Drop uses of CHARGER regulator, manage registers directly in power
  supply driver instead
- Link to v2: https://lore.kernel.org/r/20240715-max77693-charger-extcon-v2-0-0838ffbb18c3@gmail.com

Changes in v2:
- Changed to use monitored-battery for charge current value
- Both current limit variables are now set by the CHARGER regulator
- Link to v1: https://lore.kernel.org/r/20240530-max77693-charger-extcon-v1-0-dc2a9e5bdf30@gmail.com

---
Artur Weber (10):
      dt-bindings: power: supply: max77693: Add monitored-battery property
      dt-bindings: power: supply: max77693: Add maxim,usb-connector property
      power: supply: max77693: Expose input current limit and CC current properties
      power: supply: max77693: Set charge current limits during init
      power: supply: max77693: Add USB extcon detection for enabling charging
      power: supply: max77693: Add support for detecting and enabling OTG
      power: supply: max77693: Set up charge/input current according to cable type
      ARM: dts: samsung: exynos4212-tab3: Add battery node with charge current value
      ARM: dts: samsung: exynos4212-tab3: Add USB connector node
      ARM: dts: samsung: exynos4212-tab3: Drop CHARGER regulator

 .../bindings/power/supply/maxim,max77693.yaml      |  15 +
 arch/arm/boot/dts/samsung/exynos4212-tab3.dtsi     |  22 +-
 drivers/power/supply/Kconfig                       |   1 +
 drivers/power/supply/max77693_charger.c            | 304 ++++++++++++++++++++-
 include/linux/mfd/max77693-private.h               |  12 +
 5 files changed, 339 insertions(+), 15 deletions(-)
---
base-commit: 0c3836482481200ead7b416ca80c68a29cfdaabd
change-id: 20240525-max77693-charger-extcon-9ebb7bad83ce

Best regards,
-- 
Artur Weber <aweber.kernel at gmail.com>