[PATCH v6 0/6] reset: gpio: ASoC: shared GPIO resets

[Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>]

Hi,

Dependencies / Merging
======================
1. Depends on !GPIOLIB stub:
   https://lore.kernel.org/all/20240125081601.118051-3-krzysztof.kozlowski@xxxxxxxxxx/

2. Patch #2 (cpufreq: do not open-code of_phandle_args_equal()) and patch #4
   (reset: Instantiate reset GPIO controller for shared reset-gpios) depend on OF
   change (patch #1).

Changes in v6
=============
1. reset/core.c: Add check for number of GPIO cells==2 (Neil).
2. Add Rb/Ack tags.

Changes in v5
=============
1. Minor comments from Philipp: missing cleanup.h, correct indentation of
   pr_err(), shorten gpio_device_find_by_fwnode() line.
2. Acks/Rbs.

Changes in v4
=============
1. New patches:
   of: add of_phandle_args_equal() helper
   cpufreq: do not open-code of_phandle_args_equal()

2. reset-gpio.c:
   - Drop unneeded comment (Bartosz), add Rb tag.
   - Do not assign of_node.

3. reset/core.c:
   - Implement most of Bartosz feedback (I responded to one which I did not
     implement) and comments from Philipp.
   - Expect either rcdev->of_args or rcdev->of_node.
   - Drop __reset_gpios_args_match() and use common helper (Philipp).
   - Move declarations of automatic-cleanup variables in
     __reset_add_reset_gpio_lookup() to place of use (Bartosz).
   - Separate gpio_device_get_label() and kstrdup() (Philipp).
   - Correct doc for __reset_add_reset_gpio_device(), rewrite few comments.
   - Drop unneeded "r" variable in __reset_find_rcdev() (Philipp).
   - Drop of_phandle_args initialization in __of_reset_control_get (Philipp).
   - Check if CONFIG_RESET_GPIO is enabled before trying to look up reset-gpios.

4. Drop Chris' patch: "i2c: muxes: pca954x: Allow sharing reset GPIO", because
   discussion is on going.

Changes in v3
=============
1. reset-gpio.c:
  - Add reset_gpio_of_xlate (Philipp).
  - reset_gpio_of_args_put->reset_gpio_of_node_put (Philipp).
  - Expect via platdata of_phandle_args.
  - Do not call device_set_node() to attach itself to reset consumer
    (the final device).  This was questionable idea in the first place.
    Bartosz suggested to use GPIO_LOOKUP to solve this.

2. reset/core.c, implement Philipp's feedback. That was a lot:
  - Commit msg fixes.
  - Add new platform_device earlier, when reset core found "reset-gpios" but
    not "resets".
  - Do not overwrite of_phandle_args.
  - Expect matching .of_reset_n_cells.
  - Pass of_phandle_args as platdata to reset-gpio.
  - Rename reset_gpio_device->reset_gpio_lookup and others. Fix few comments
    and code cleanup pointed on review.
  - From Bartosz:
    Use GPIO_LOOKUP and a lot of cleanup.h in __reset_add_reset_gpio_lookup().

3. Include here Chris' patch: "i2c: muxes: pca954x: Allow sharing reset GPIO".

Changes in v2
=============
1. wsa884x.c: add missing return in wsa884x_get_reset(), correct comment.
2. qcom,wsa8840.yaml: fix oneOf syntax.
3. reset-gpio.c:
   - Fix smatch warning on platdata evaluation.
   - Parse GPIO args and store them in rc.of_args.
4. reset/core.c:
   - Revise approach based on Bartosz comments: parse the reset-gpios phandle
     with arguments, do not use deprecated API and do not rely on gpio_desc
     pointer.
   - Create a list of instantiated platform devices to avoid any duplicates.
   - After creating reset-gpio platform device, try to get new reset controller
     or return EPROBE_DEFER.
   - Drop the "cookie" member and add new "of_args" to "struct
     reset_controller_dev".

Description
===========

We have at least few cases where hardware engineers decided to use one
powerdown/shutdown/reset GPIO line for multiple devices:

1. WSA884x (this and previous patch):
https://lore.kernel.org/all/b7aeda24-d638-45b7-8e30-80d287f498f8@xxxxxxxxxxxxx/
2. https://lore.kernel.org/all/20231027033104.1348921-1-chris.packham@xxxxxxxxxxxxxxxxxxx/
3. https://lore.kernel.org/lkml/20191030120440.3699-1-peter.ujfalusi@xxxxxx/
4. https://lore.kernel.org/all/20211018234923.1769028-1-sean.anderson@xxxxxxxx/
5. https://social.treehouse.systems/@marcan/111268780311634160

I try to solve my case, hopefuly Chris' (2), partially Sean's (4) and maybe
Hectors (5), using Rob's suggestion:

https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@xxxxxxxxxxxxxxxxxx/

Best regards,
Krzysztof

Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
Cc: Bartosz Golaszewski <brgl@xxxxxxxx>
Cc: Sean Anderson <sean.anderson@xxxxxxxx>

Krzysztof Kozlowski (6):
  of: Add of_phandle_args_equal() helper
  cpufreq: do not open-code of_phandle_args_equal()
  reset: gpio: Add GPIO-based reset controller
  reset: Instantiate reset GPIO controller for shared reset-gpios
  ASoC: dt-bindings: qcom,wsa8840: Add reset-gpios for shared line
  ASoC: codecs: wsa884x: Allow sharing reset GPIO

 .../bindings/sound/qcom,wsa8840.yaml          |  11 +-
 MAINTAINERS                                   |   5 +
 drivers/reset/Kconfig                         |   9 +
 drivers/reset/Makefile                        |   1 +
 drivers/reset/core.c                          | 224 +++++++++++++++++-
 drivers/reset/reset-gpio.c                    | 119 ++++++++++
 include/linux/cpufreq.h                       |   3 +-
 include/linux/of.h                            |  16 ++
 include/linux/reset-controller.h              |   4 +
 sound/soc/codecs/wsa884x.c                    |  53 ++++-
 10 files changed, 419 insertions(+), 26 deletions(-)
 create mode 100644 drivers/reset/reset-gpio.c

-- 
2.34.1