Documentation: firmware-guide: gpio-properties: Clarify Explicit and Implicit

Clarify the Explicit and Implicit meanings in the table of Pull Bias.

While at it, distinguish pull bias keywords used in ACPI by using bold
font in the table of the respective terms.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPI: docs: gpio-properties: Unify ASL style for GPIO examples

GPIO examples of ASL in the board.rst, enumeration.rst and gpio-properties.rst
are not unified. Unify them for better reader experience.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: firmware-guide: gpio-properties: Add note to SPI CS case

Historically ACPI has no means of the GPIO polarity and thus
the SPISerialBus() resource defines it on the per-chip basis.
In order to avoid an ambiguity, the GPIO polarity is considered
being always Active High.

Add note about this to the respective documentation file.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: ACPI: add new rule for gpio-line-names

The gpio-line-names lists must respect some rules.

This patch adds a new rule in documentation, to avoid
the use of duplicate names in the same gpiochip.

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: ACPI: explain how to use gpio-line-names

The "gpio-line-names" declaration is not fully
documented, so can be useful to add some important
information and one more example.

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: firmware-guide: gpio-properties: Clarify initial output state

GpioIo() doesn't provide an explicit state for an output pin.
Linux tries to be smart and uses a common sense based on other
parameters. Document how it looks like in the code.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: firmware-guide: gpio-properties: active_low only for GpioIo()

It appears that people may misinterpret active_low field in _DSD
for GpioInt() resource. Add a paragraph to clarify this.

Reported-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: firmware-guide: gpio-properties: Fix factual mistakes

Fix factual mistakes and style issues in GPIO properties document.
This converts IoRestriction from InputOnly to OutputOnly as pins
in the example are used as outputs.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: ACPI: move gpio-properties.txt to firmware-guide/acpi and convert to reST

This converts the plain text documentation to reStructuredText format
and adds it to Sphinx TOC tree.

No essential content change.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>