[PATCH v2 0/4] hwmon: (pmbus) Add support for MAX20826 and similar devices

[Nuno Sá]

Add support for Analog Devices MAX20826, MAX20855B, MAX20908,
MAX20912 and MAX20916 dual-output multiphase PMBus voltage regulator
controllers.

This follows up on the earlier MAX20912/MAX20916 submission and the
review discussion around it [1]. Compared to that minimal driver, this
series covers the full MAX20826 family and implements the device-specific
pieces discussed there: optional EN GPIO handling, non-standard phase
reporting, direct address mode, and regulator support.

The first patches prepare PMBus core support needed by the driver: allow
up to 16 phases and add a device-specific block-read hook. The remaining
patches add the DT binding and the MAX20826-family driver/documentation.

Note this revision is based on hwmon-next as the driver now makes use of
pmbus_read_smbus_i2c_block_data().

[1]: https://lore.kernel.org/linux-hwmon/20260707122701.751878-3-fredchen.openbmc@xxxxxxxxx/

Changes in v2:
- Dropped v1 patch 1 ("hwmon: (pmbus/core) fix regulator enable/disable"):
  the proper fix is to make pmbus_update_byte_data() only ever return 0 or
  an error code, which is now upstream as a19038a200f1 ("hwmon: (pmbus) Fix
  return value from pmbus_update_byte_data()").
- Patch 1:
    - No changes.
- Patch 2:
    - Fixed the read_block_data() comment to describe the actual API.
    - Explained in the commit message why the hook is needed.
- Patch 3:
    - Added the (required) vdd3p3-supply property.
    - Added the regulators node with the vout0 and vout1 subnodes.
    - Added the adi,rail-a-high-speed and adi,rail-b-high-speed properties.
- Patch 4:
    - Dropped the <linux/mod_devicetable.h> include.
    - Use pmbus_read_smbus_i2c_block_data() instead of the driver specific
      block read helper, which read past the end of its buffer and did not
      return the actual data size.
    - Use pmbus_update_byte_data() instead of the driver specific
      read-modify-write helper for everything outside of probe().
    - The source of the output voltage of each rail is now given in firmware
      with adi,rail-{a,b}-high-speed instead of through a writable sysfs
      attribute. in[2-3]_high_speed_en and in_high_speed_bus are now debugfs
      entries.
    - Split max20826_regulator_do_enable() out of
      max20826_regulator_enable() and use it in max20826_detect_phases(), so
      that the AVSBus workaround is applied when forcing the rail on.
    - Fixed a NULL pointer dereference in max20826_setup_vout_format(): it
      runs before pmbus_do_probe() but reached pmbus_set_page().
    - Make sure we swith to RAIL_A when RAIL_B is not available.
- Link to v1: https://patch.msgid.link/20260728-hwmon-max20826-support-v1-0-224766e0acd1@xxxxxxxxxx

---
Nuno Sá (4):
      hwmon: (pmbus/core) increase number of phases and add new mask
      hwmon: (pmbus/core) Add mapping function to pmbus_read_block_data()
      dt-bindings: hwmon/pmbus: Document MAX20826 and similar devices
      hwmon: (pmbus) add support for MAX20826 and similar devices

 .../bindings/hwmon/pmbus/adi,max20826.yaml         |  102 ++
 Documentation/hwmon/index.rst                      |    1 +
 Documentation/hwmon/max20826.rst                   |  139 +++
 MAINTAINERS                                        |    9 +
 drivers/hwmon/pmbus/Kconfig                        |   19 +
 drivers/hwmon/pmbus/Makefile                       |    1 +
 drivers/hwmon/pmbus/max20826.c                     | 1044 ++++++++++++++++++++
 drivers/hwmon/pmbus/pmbus.h                        |   10 +-
 drivers/hwmon/pmbus/pmbus_core.c                   |   24 +-
 9 files changed, 1346 insertions(+), 3 deletions(-)
---
base-commit: f614eea73fd43d0e8057fcc49465aaa4d2024975
change-id: 20260728-hwmon-max20826-support-c82ee65118ec
--

Thanks!
- Nuno Sá