[PATCH v4 0/2] add support for MCP998X

[<victor.duicu@microchip.com>]

From: Victor Duicu <victor.duicu@microchip.com>

Add support for Microchip MCP998X/33 and MCP998XD/33D Multichannel Automotive Temperature Monitor Family.

The chips in the family have different numbers of external channels, ranging from 1 (MCP9982) to 4 channels (MCP9985).
Reading diodes in anti-parallel connection is supported by MCP9984/85/33 and MCP9984D/85D/33D.
Dedicated hardware shutdown circuitry is present only in MCP998XD and MCP9933D.

Current version of driver does not support interrupts, events and data buffering.

Differences related to previous patch:
v4:
- lock beta parameters to default value of beta-autodetect.
  Remove beta parameters and checks from devicetree.
- lock temperature range to extended.
  This change avoids the issue of the average filter using raw values
  with different scales when changing the range.
- change driver to wait an amount of time before reading a raw value
  to ensure it is valid.
- change driver to stop calculating the physical temp when reading
  in_tempx_raw. Reading from in_tempx_raw will return the raw value.
  The physical temp will be calculated with in_tempx_raw, scale and
  offset parameters.
- add scale parameter to channel definition.
- initialise chips with "D" to work in Run state and those without
  in Standby state.
- when activating the low pass filter for chips without "D",
  set the power state to RUN to ensure fresh values for the average.
- add minimum and maximum to microchip,beta1 and microchip,beta2 in yaml.
- rename microchip,resistance-comp-ch1-2-enable and
  microchip,resistance-comp-ch3-4-enable to
  microchip,parasitic-res-on-channel1-2
  and microchip,parasitic-res-on-channel3-4
  and edit description in yaml.
- add conditional logic to check if the chip supports APDD
  and force default values where necessary in yaml.
- edit comments and coding style.
- replace asm/div64.h with linux/math64.h.
- add delay.h to includes.
- redefine mcp9982_sampl_fr with new structure division.
- in mcp9982_priv remove dev_name,extended_temp_range and beta_values.
  Add run_state, wait_before_read, time_limit and pointer to chip
  structure to remove all instances of matching strings.
  Reorder parameters for memory optimization.
- in mcp9982_features add flags to know if the chip has thermal shutdown
  circuitry and supports APDD.
- in mcp9982_read_avail() rework verification of chip type in sampling
  frequency case.
- in mcp9982_read_raw() rework switch in low pass filter case.
- in mcp9982_parse_of_config() replace generic -EINVAL code
  with -E2BIG and -EOVERFLOW. 

v3:
- move beta parameters to devicetree.
- change the name of the interrupts and add
  check to match them to the device in yaml.
- remove label for device and remove "0x" from
  channel registers in example in yaml.
- edit comments in yaml and driver.
- add minItems to interrupts in yaml.
- rename microchip,recd12 and microchip,recd34 to
  microchip,resistance-comp-ch1-2-enable
  and microchip,resistance-comp-ch3-4-enable.
- rename microchip,apdd-state to microchip,enable-anti-parallel.
- add static to mcp9982_3db_values_map_tbl to fix
  kernel test robot warning.
- in mcp9982_init() add check to ensure that hardware
  shutdown feature can't be overridden.
- replace div_u64_rem with do_div and add
  asm/div64.h to includes.
- remove unused includes.
- add iio_chan_spec in the macro definition of MCP9982_CHAN.
- remove MCP9982_EXT_BETA_ENBL.
- in mcp9982_init() replace regmap_assign_bits
  with regmap_write when setting beta compensation.
- remove custom attribute enable_extended_temp_range and
  map it to IIO_CHAN_INFO_OFFSET.
- add unsigned to int variables that allow it.
- reorder parameters in mcp9982_priv, change some
  from int to bool, add const to labels and add dev_name.
- add check for chips with "D" in the name to not
  allow sampling frequencies lower than 1 to
  prevent overriding of hardware shutdown.
- remove mcp9982_attributes.
- move mcp9982_calc_all_3db_values() to before
  mcp9982_init().
- use MICRO instead of number constant.
- in mcp9982_write_raw replace ">=" with "==".
- rename index2 to idx in mcp9982_read_raw().
- remove i2c_set_clientdata() in mcp9982_probe().
- since there are no more custom ABI attributes
  the testing file was removed.

v2:
- move hysteresis, extended temperature range and beta parameters
  from devicetree into user space.
- edit comments in yaml and driver.
- remove "|" in descpriptions, remove "+" from PatternProperties in yaml.
- add default to microchip,ideality-factor, delete blank lines and wrap to
  80 chars in yaml.
- remove variables with upper case.
- add check for microchip,apdd-state and microchip,recd34 in yaml.
- improve coding style in driver code.
- add includes for all functions used.
- rename MCP9982_INT_HIGH_BYTE_ADDR to MCP9982_INT_VALUE_ADDR and
  MCP9982_INT_LOW_BYTE_ADDR to MCP9982_FRAC_VALUE_ADDR.
- remove custom attribute running_average_window and
  running_average_window_available and map them to a low pass filter.
- update sysfs-bus-iio-temperature-mcp9982 to reflect current
  driver attributes and point to next kernel version (6.17).
- use compound literal to define driver channels.
- replace device_property_read_string() with i2c_get_match_data() to read
  chip name from devicetree.
- remove MCP9982_DEV_ATTR and mcp9982_prep_custom_attributes().
- remove client, chip_name, iio_info from mcp9982_priv.
- replace sprintf() with sysfs_emit().
- remove error messages which are triggered by keyboard input.
- replace devm_kzalloc() with devm_kcalloc(), array mcp9982_chip_config[] with
  individual structures, device_property_present() with device_property_read_bool().
- reordered parameters in mcp9982_features and mcp9982_priv to optimize memory
  allocation.
- remove .endianness from channel properties.
- change name of some parameters in mcp9982_priv.
- add check for reg value 0 from devicetree (channel 0 is for internal temperature
  and can't be disabled).

v1:
- inital version.


Victor Duicu (2):
  dt-bindings: iio: temperature: add support for MCP998X
  iio: temperature: add support for MCP998X

 .../iio/temperature/microchip,mcp9982.yaml    | 203 ++++
 MAINTAINERS                                   |   7 +
 drivers/iio/temperature/Kconfig               |  10 +
 drivers/iio/temperature/Makefile              |   1 +
 drivers/iio/temperature/mcp9982.c             | 889 ++++++++++++++++++
 5 files changed, 1110 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/temperature/microchip,mcp9982.yaml
 create mode 100644 drivers/iio/temperature/mcp9982.c


base-commit: 788c57f4766bd5802af9918ea350053a91488c60
-- 
2.48.1