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Diffstat (limited to 'Documentation/firmware-guide/acpi/gpio-properties.rst')
| -rw-r--r-- | Documentation/firmware-guide/acpi/gpio-properties.rst | 35 |
1 files changed, 24 insertions, 11 deletions
diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst index eaec732cc77c..db0c0b1f3700 100644 --- a/Documentation/firmware-guide/acpi/gpio-properties.rst +++ b/Documentation/firmware-guide/acpi/gpio-properties.rst @@ -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 |