[PATCH v4 0/6] hwmon: (lm63) Add Sensylink CTF2301 support

[Troy Mitchell <troy.mitchell@linux.dev>]

Sensylink CTF2301 is a system-level thermal management solution chip.

The CTF2301 is an I2C/SMBus compatible device featuring:
  - One local temperature sensor with +/-0.5 degree C accuracy and
    0.0625 degree C resolution.
  - One remote temperature sensor for external diode-connected
    transistors, offering +/-1 degree C accuracy and 0.125 degree C
    resolution (temperature range: -40 degree C to +125 degree C).
  - An integrated PWM fan controller capable of operating in two modes:
      1. Direct-DCY: Open-loop direct duty cycle control.
      2. Auto-Temp: Closed-loop automatic fan speed control based on
         measured temperature.
  - A 1-channel fan speed monitor (TACH input) for RPM measurement.

As Guenter pointed out on v1, the CTF2301 register map is a near match
for the LM63/LM96163 family (local and remote temperature, tachometer and
PWM fan control), so this version drops the standalone ctf2301 driver
and instead adds CTF2301 as a new chip type in the existing lm63 driver.
This reuses the shared temperature, limit, alarm and PWM handling instead
of duplicating it.

The CTF2301-specific differences are handled on top of lm63: 12-bit local
temperature input and high-limit values, nine conversion rates, 12
fan-control lookup table entries, and optional 22.5 kHz high-resolution
PWM. When no IRQ is described, the shared ALERT/TACH pin is configured as
a tachometer input. The LM63 family can also register as a thermal cooling
device when the device tree provides the #cooling-cells property.

Tested on a SpacemiT K3 CoM260 by booting an initramfs and verifying the
CTF2301 probe. Temperature, tachometer, PWM, and conversion-rate behavior
were checked against direct I2C register accesses and the datasheet.

Datasheet:
https://www.sensylink.com/upload/1/net.sensylink.portal/1689557281035.pdf

Register description:
https://github.com/TroyMitchell911/ctf2301-datasheet

Signed-off-by: Troy Mitchell <troy.mitchell@linux.dev>
---
Changes in v4:
- Rebase onto v7.3-rc1, which includes the SpacemiT I2C timing
  prerequisite, and remove the obsolete dependency note.
- Do not add the SENSORS_LM63 THERMAL dependency suggested on v3 because
  CONFIG_THERMAL is boolean and v7.3-rc1 removes such tautological
  expressions.
- Preserve the upstream five-bit PWM frequency multiplier mask in the
  LM63 initialization error-handling path.
- Sort the chip type enum and remove redundant CTF2301 8-bit local
  temperature cache updates.
- Serialize CTF2301 12-bit local temperature cache reads.
- Keep PWM configuration caches synchronized after partial I2C write
  failures.
- Override the CoM260 I2C6 pin configuration through &i2c6_1_cfg,
  as suggested by Yixun.
- Add Krzysztof's Acked-by and Reviewed-by tags.
- Link to v3: https://patch.msgid.link/20260805-ctl2301-v3-0-fd4b8ffb5b0d@linux.dev

Changes in v3:
- Add the Sensylink website link to the vendor-prefix commit.
- Preserve the optional interrupt from the trivial-devices binding.
- Explain in the commit message of patch 3/6 why CTF2301 cannot use
  national,lm63 as a fallback compatible.
- Check both bytes of CTF2301 local temperature values before caching them.
- Use the schema-valid 25 mA drive strength for the K3 I2C6 pins.
- Link to v2: https://patch.msgid.link/20260721-ctl2301-v2-0-ef5fb342872a@linux.dev

Changes in v2:
- Replace the standalone CTF2301 driver with a new lm63 chip type, as
  suggested by Guenter, reusing the existing temperature, limit, alarm,
  tachometer, PWM, and automatic fan-control paths.
- Add the temperature thresholds, alarms, and automatic fan-control lookup
  table support which were missing from the v1 driver.
- Handle CTF2301-specific 12-bit local temperature values, nine conversion
  rates, 12 lookup table entries, shared ALERT/TACH pin, and optional
  22.5 kHz high-resolution PWM.
- Propagate SMBus failures from lm63 initialization and write paths.
- Add optional thermal cooling-device support for the LM63 family using
  the existing manual PWM control path.
- Move the National LM63-family compatibles from trivial-devices.yaml to a
  dedicated binding which permits #cooling-cells.
- Add CTF2301 to the LM63-family binding instead of keeping the standalone
  schema from v1. Do not declare #cooling-cells on K3 CoM260 yet because
  the board has no thermal consumer.
- Fix the binding errors reported by Rob by using a plain compatible string
  and wrapping the description.
- Document CTF2301 support in the lm63 hwmon documentation and provide the
  detailed register description used for review.
- Add the K3 CoM260 I2C6 pinctrl state and CTF2301 device node for hardware
  testing.
- Link to v1: https://lore.kernel.org/r/20250916-ctl2301-v1-0-97e7c84f2c47@linux.dev

To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>
To: Paul Walmsley <pjw@kernel.org>
To: Palmer Dabbelt <palmer@dabbelt.com>
To: Albert Ou <aou@eecs.berkeley.edu>
To: Alexandre Ghiti <alex@ghiti.fr>
To: Yixun Lan <dlan@kernel.org>
To: Jonathan Corbet <corbet@lwn.net>
To: Shuah Khan <skhan@linuxfoundation.org>
To: Randy Dunlap <rdunlap@infradead.org>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-hwmon@vger.kernel.org
Cc: linux-riscv@lists.infradead.org
Cc: spacemit@lists.linux.dev
Cc: linux-doc@vger.kernel.org

---
Troy Mitchell (6):
      dt-bindings: vendor-prefixes: Add Sensylink
      dt-bindings: hwmon: Move LM63 family to a dedicated binding
      dt-bindings: hwmon: Add Sensylink CTF2301
      hwmon: (lm63) Add Sensylink CTF2301 support
      riscv: dts: spacemit: Add K3 I2C6 pinctrl state
      riscv: dts: spacemit: Add CTF2301 on K3 CoM260

 .../devicetree/bindings/hwmon/national,lm63.yaml   |  55 +++
 .../devicetree/bindings/trivial-devices.yaml       |   6 -
 .../devicetree/bindings/vendor-prefixes.yaml       |   2 +
 Documentation/hwmon/lm63.rst                       |  22 ++
 arch/riscv/boot/dts/spacemit/k3-com260.dtsi        |  17 +
 arch/riscv/boot/dts/spacemit/k3-pinctrl.dtsi       |  11 +
 drivers/hwmon/Kconfig                              |   8 +-
 drivers/hwmon/lm63.c                               | 426 +++++++++++++++++----
 8 files changed, 462 insertions(+), 85 deletions(-)
---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20250916-ctl2301-0416b073c280

Best regards,
--  
Troy Mitchell <troy.mitchell@linux.dev>