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

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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>
This commit is contained in:
Andy Shevchenko 2023-02-13 22:40:05 +02:00 committed by Rafael J. Wysocki
parent faffb0831a
commit 3082d7efd7
1 changed files with 24 additions and 11 deletions
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35
Documentation/firmware-guide/acpi/gpio-properties.rst
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@ -67,17 +67,30 @@ state of the output pin which driver should use during its initialization.
Linux tries to use common sense here and derives the state from the bias Linux tries to use common sense here and derives the state from the bias
and polarity settings. The table below shows the expectations: and polarity settings. The table below shows the expectations:
========= ============= ============== +-------------+-------------+-----------------------------------------------+
Pull Bias Polarity Requested... | Pull Bias | Polarity | Requested... |
========= ============= ============== +=============+=============+===============================================+
Implicit x AS IS (assumed firmware configured for us) | Implicit |
Explicit x (no _DSD) as Pull Bias (Up == High, Down == Low), +-------------+-------------+-----------------------------------------------+
assuming non-active (Polarity = !Pull Bias) | **Default** | x | AS IS (assumed firmware configured it for us) |
Down Low as low, assuming active +-------------+-------------+-----------------------------------------------+
Down High as low, assuming non-active | Explicit |
Up Low as high, assuming non-active +-------------+-------------+-----------------------------------------------+
Up High as high, assuming active | **None** | x | AS IS (assumed firmware configured it for us) |
========= ============= ============== | | | with no Pull Bias |
+-------------+-------------+-----------------------------------------------+
| **Up** | x (no _DSD) | |
| +-------------+ as high, assuming non-active |
| | Low | |
| +-------------+-----------------------------------------------+
| | High | as high, assuming active |
+-------------+-------------+-----------------------------------------------+
| **Down** | x (no _DSD) | |
| +-------------+ as low, assuming non-active |
| | High | |
| +-------------+-----------------------------------------------+
| | Low | as low, assuming active |
+-------------+-------------+-----------------------------------------------+
That said, for our above example the both GPIOs, since the bias setting That said, for our above example the both GPIOs, since the bias setting
is explicit and _DSD is present, will be treated as active with a high is explicit and _DSD is present, will be treated as active with a high