Commit ec3576ea authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Rafael J. Wysocki
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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: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent d8f9176b

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

+6 −0
Original line number Diff line number Diff line
@@ -99,6 +99,12 @@ native:: 
      }

  }



Note, that 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 a chain of negations, the GPIO polarity is considered being

Active High. Even for the cases when _DSD() is involved (see the example

above) the GPIO CS polarity must be defined Active High to avoid ambiguity.



Other supported properties

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