[PATCH RFC 0/3] Verify bias functionality for pinctrl_paris driver through new gpio test

["Nícolas F. R. A. Prado" <nfraprado@collabora.com>]

This series was motivated by the regression fixed by 166bf8af9122
("pinctrl: mediatek: common-v2: Fix broken bias-disable for
PULL_PU_PD_RSEL_TYPE"). A bug was introduced in the pinctrl_paris driver
which prevented certain pins from having their bias configured.

Running this test on the mt8195-tomato platform with the test plan
included below[1] shows the test passing with the fix applied, but failing
without the fix:

With fix:
  $ ./gpio-setget-config.py
  TAP version 13
  # Using test plan file: ./google,tomato.yaml
  1..3
  ok 1 pinctrl_paris.34.pull-up
  ok 2 pinctrl_paris.34.pull-down
  ok 3 pinctrl_paris.34.disabled
  # Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0

Without fix:
  $ ./gpio-setget-config.py
  TAP version 13
  # Using test plan file: ./google,tomato.yaml
  1..3
  # Bias doesn't match: Expected pull-up, read pull-down.
  not ok 1 pinctrl_paris.34.pull-up
  ok 2 pinctrl_paris.34.pull-down
  # Bias doesn't match: Expected disabled, read pull-down.
  not ok 3 pinctrl_paris.34.disabled
  # Totals: pass:1 fail:2 xfail:0 xpass:0 skip:0 error:0

In order to achieve this, the first patch exposes bias configuration
through the GPIO API in the pinctrl_paris driver, patch 2 extends the
gpio-mockup-cdev utility for use by patch 3, and patch 3 introduces a
new GPIO kselftest that takes a test plan in YAML, which can be tailored
per-platform to specify the configurations to test, and sets and gets
back each pin configuration to verify that they match and thus that the
driver is behaving as expected.

Since the GPIO uAPI only allows setting the pin configuration, getting
it back is done through pinconf-pins in the pinctrl debugfs folder.

The test currently only verifies bias but it would be easy to extend to
verify other pin configurations.

The test plan YAML file can be customized for each use-case and is
platform-dependant. For that reason, only an example is included in
patch 3 and the user is supposed to provide their test plan. That said,
the aim is to collect test plans for ease of use at [2].

[1] This is the test plan used for mt8195-tomato:

- label: "pinctrl_paris"
  tests:
  # Pin 34 has type MTK_PULL_PU_PD_RSEL_TYPE and is unused.
  # Setting bias to MTK_PULL_PU_PD_RSEL_TYPE pins was fixed by
  # 166bf8af9122 ("pinctrl: mediatek: common-v2: Fix broken bias-disable for PULL_PU_PD_RSEL_TYPE")
  - pin: 34
    bias: "pull-up"
  - pin: 34
    bias: "pull-down"
  - pin: 34
    bias: "disabled"

[2] https://github.com/kernelci/platform-test-parameters

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
---
Nícolas F. R. A. Prado (3):
      pinctrl: mediatek: paris: Expose more configurations to GPIO set_config
      selftest: gpio: Add wait flag to gpio-mockup-cdev
      selftest: gpio: Add a new set-get config test

 drivers/pinctrl/mediatek/pinctrl-paris.c           |  20 +--
 tools/testing/selftests/gpio/Makefile              |   2 +-
 tools/testing/selftests/gpio/gpio-mockup-cdev.c    |  14 +-
 .../gpio-set-get-config-example-test-plan.yaml     |  15 ++
 .../testing/selftests/gpio/gpio-set-get-config.py  | 183 +++++++++++++++++++++
 5 files changed, 220 insertions(+), 14 deletions(-)
---
base-commit: 6a7917c89f219f09b1d88d09f376000914a52763
change-id: 20240906-kselftest-gpio-set-get-config-6e5bb670c1a5

Best regards,
-- 
Nícolas F. R. A. Prado <nfraprado@collabora.com>