Re: [PATCH v4 0/3] Add support for LTC2688

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 25 Feb 2022 14:01:26 +0100
Nuno Sá <nuno.sa@analog.com> wrote:

Hi Nuno,

Given we are close to the end of this cycle and Andy has been heavily involved
in review of this one so I want to give more time for Andy to potentially take
another look..

Hence, I'm going to do something unusual and push out an extra-testing branch with this
on so we can get through the autobuilder tests in parallel with that extra time.

So, applied to the new extra-testing branch of iio.git with the intent to apply
it to togreg later in a day or two subject to any last minute feedback.

Thanks,

Jonathan


> The ABI defined for this driver has some subtleties that were previously
> discussed in this RFC [1]. This might not be the final state but,
> hopefully, we are close to it:
> 
> toggle mode channels:
> 
>  * out_voltageY_toggle_en
>  * out_voltageY_raw0
>  * out_voltageY_raw1
>  * out_voltageY_symbol
> 
> dither mode channels:
> 
>  * out_voltageY_dither_en
>  * out_voltageY_dither_raw
>  * out_voltageY_dither_raw_available
>  * out_voltageY_dither_offset
>  * out_voltageY_dither_frequency
>  * out_voltageY_dither_frequency_available
>  * out_voltageY_dither_phase
>  * out_voltageY_dither_phase_available
> 
> Default channels won't have any of the above ABIs. A channel is toggle
> capable if the devicetree 'adi,toggle-mode' flag is set. For dither, the
> assumption is more silent. If 'adi,toggle-mode' is not given and a
> channel is associated with a TGPx pin through 'adi,toggle-dither-input',
> then the channel is assumed to be dither capable (there's no point in
> having a dither capable channel without an input clock).
> 
> changes in v2:
> 
>  ltc2688:
>   * Use local buffer for regmap read. Do not assume that reg is part of
> larger buffer;
>   * Renamed GPIO to "clr" so that is consistent with the datasheet;
>   * Renamed 'mask' and 'm' to info. 'mask' is a thing from the past;
>   * Removed 'LTC2688_CHAN_TOGGLE()' and defined to static ext_info arrays;
>   * Use 'regmap_set_bits' to set external ref;
>   * Use FIELD_{PREP|GET} for dither amplitude and channel calibbias where
> only 13bits are used;
>   * Use 'regmap_write()' instead of update_bits for channels settings;
>   * Init 'val' at the beginning of the channel configuration loop
> (and drop mask);
>   * Comment 'ltc2688_reg_writable()' to account for the special condition;
>   * Kmemdup default channels so that it can be safely changed per probed
> device;
>   * Replace extended info multiplexer functions by individual functions;
>   * Use raw0 ABI for toggle channels;
>   * Use dedicated offset ABI for dither channels;
>   * Misc changes (spell fixes, blank lines...);
>   * Have a clock property per channel. Note that we this I moved to OF
> since we now have to use 'devm_get_clk_from_child()' which is using
> device_node. Note that I could use 'to_of_node()' but mixing of.h and
> property.h does not feel like a good idea.
> 
>  ABI:
>   * Added out_voltageY_raw0 ABI for toggle mode;
>   * Added out_voltageY_dither_offset.
> 
>  Bindings:
>   * Use standard microvolt unit;
>   * Added constrains for adi,output-range-microvolt and removed negative
> values from the dts example;
>   * Moved clocks to the channel object;
>   * Dropped clock-names;
>   * Add a dependency between 'adi,toggle-dither-input' and 'clocks'.
> 
> Changes in v3:
> 
>  ltc2688:
>   * Fix mismatch between functions and function pointers detected by kernel
> test bot; 
>   * Always use if (ret) when ret > 0 has no meaning;
>   * Rename ltc2688_bulk_disable -> ltc2688_disable_regulators;
>   * Report dither phase in radians rather than degrees.
> 
>  ABI:
>   * Specify units for dither_phase and dither_freqency; 
>   * Say why its useful to have dither_en and toggle_en;
>   * Combine out_voltageY_raw0 and out_voltageY_raw1;
>   * Fix some description issues in out_voltageY_raw{0|1} and
> out_voltageY_symbol.
> 
>  Bindings:
>   * Remove mentions to ABI (linux specifix);
>   * Slightly rephrased VREF and adi,toggle-dither-input properties and
> suggested.
>    
> changes in v4:
> 
>  ltc2688:
>   * Use reg_size + val_size instead of plain 3 in regmap;
>   * Use out_unlock instead of unlock in goto labels;
>   * Add comma to LTC2688_CHANNEL(), ltc2688_regmap_bus and
> ltc2688_regmap_bus;
>   * Use __clear_bit() instead of clear_bit();
>   * Flip the logic in vref regulator so that error condition is handled
> first;
>   * Change to device API. With this, we need to_of_node()
> for devm_get_clk_from_child().
> 
>  ABI:
>   * Update kernel version.
> 
>  Bindings:
>   * Add Rob's Rb tag.
> 
> [1]: https://marc.info/?l=linux-iio&m=163662843603265&w=2
> 
> Nuno Sá (3):
>   iio: dac: add support for ltc2688
>   iio: ABI: add ABI file for the LTC2688 DAC
>   dt-bindings: iio: Add ltc2688 documentation
> 
>  .../ABI/testing/sysfs-bus-iio-dac-ltc2688     |   86 ++
>  .../bindings/iio/dac/adi,ltc2688.yaml         |  146 +++
>  MAINTAINERS                                   |    9 +
>  drivers/iio/dac/Kconfig                       |   11 +
>  drivers/iio/dac/Makefile                      |    1 +
>  drivers/iio/dac/ltc2688.c                     | 1071 +++++++++++++++++
>  6 files changed, 1324 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-dac-ltc2688
>  create mode 100644 Documentation/devicetree/bindings/iio/dac/adi,ltc2688.yaml
>  create mode 100644 drivers/iio/dac/ltc2688.c
>