53 lines
1.9 KiB
Plaintext
53 lines
1.9 KiB
Plaintext
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_DSD Device Properties Related to GPIO
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--------------------------------------
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With the release of ACPI 5.1 and the _DSD configuration objecte names
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can finally be given to GPIOs (and other things as well) returned by
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_CRS. Previously, we were only able to use an integer index to find
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the corresponding GPIO, which is pretty error prone (it depends on
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the _CRS output ordering, for example).
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With _DSD we can now query GPIOs using a name instead of an integer
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index, like the ASL example below shows:
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// Bluetooth device with reset and shutdown GPIOs
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Device (BTH)
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{
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Name (_HID, ...)
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Name (_CRS, ResourceTemplate ()
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{
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GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
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"\\_SB.GPO0", 0, ResourceConsumer) {15}
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GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
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"\\_SB.GPO0", 0, ResourceConsumer) {27, 31}
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})
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Name (_DSD, Package ()
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{
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ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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Package ()
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{
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Package () {"reset-gpio", Package() {^BTH, 1, 1, 0 }},
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Package () {"shutdown-gpio", Package() {^BTH, 0, 0, 0 }},
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}
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})
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}
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The format of the supported GPIO property is:
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Package () { "name", Package () { ref, index, pin, active_low }}
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ref - The device that has _CRS containing GpioIo()/GpioInt() resources,
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typically this is the device itself (BTH in our case).
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index - Index of the GpioIo()/GpioInt() resource in _CRS starting from zero.
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pin - Pin in the GpioIo()/GpioInt() resource. Typically this is zero.
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active_low - If 1 the GPIO is marked as active_low.
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Since ACPI GpioIo() resource does not have a field saying whether it is
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active low or high, the "active_low" argument can be used here. Setting
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it to 1 marks the GPIO as active low.
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In our Bluetooth example the "reset-gpio" refers to the second GpioIo()
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resource, second pin in that resource with the GPIO number of 31.
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