Commit 3082d7ef authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Rafael J. Wysocki
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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: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent faffb083

Documentation/firmware-guide/acpi/gpio-properties.rst

+24 −11
Original line number Diff line number Diff line
@@ -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

and polarity settings. The table below shows the expectations:



=========  =============  ==============

Pull Bias     Polarity     Requested...

=========  =============  ==============

Implicit     x            AS IS (assumed firmware configured for us)

Explicit     x (no _DSD)  as Pull Bias (Up == High, Down == Low),

                          assuming non-active (Polarity = !Pull Bias)

Down         Low          as low, assuming active

Down         High         as low, assuming non-active

Up           Low          as high, assuming non-active

Up           High         as high, assuming active

=========  =============  ==============

+-------------+-------------+-----------------------------------------------+

| Pull Bias   | Polarity    | Requested...                                  |

+=============+=============+===============================================+

| Implicit                                                                  |

+-------------+-------------+-----------------------------------------------+

| **Default** | x           | AS IS (assumed firmware configured it for us) |

+-------------+-------------+-----------------------------------------------+

| Explicit                                                                  |

+-------------+-------------+-----------------------------------------------+

| **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

is explicit and _DSD is present, will be treated as active with a high