• Mika Westerberg's avatar
    gpio / ACPI: Add support for _DSD device properties · 0d9a693c
    Mika Westerberg authored
    With release of ACPI 5.1 and _DSD method we can finally name GPIOs (and
    other things as well) returned by _CRS. Previously we were only able to
    use integer index to find the corresponding GPIO, which is pretty error
    prone if the order changes.
    With _DSD we can now query GPIOs using name instead of an integer index,
    like the below example shows:
      // Bluetooth device with reset and shutdown GPIOs
      Device (BTH)
          Name (_HID, ...)
          Name (_CRS, ResourceTemplate ()
              GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
                      "\\_SB.GPO0", 0, ResourceConsumer) {15}
              GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
                      "\\_SB.GPO0", 0, ResourceConsumer) {27, 31}
          Name (_DSD, Package ()
              Package ()
                  Package () {"reset-gpio", Package() {^BTH, 1, 1, 0 }},
                  Package () {"shutdown-gpio", Package() {^BTH, 0, 0, 0 }},
    The format of the supported GPIO property is:
      Package () { "name", Package () { ref, index, pin, active_low }}
      ref - The device that has _CRS containing GpioIo()/GpioInt() resources,
            typically this is the device itself (BTH in our case).
      index - Index of the GpioIo()/GpioInt() resource in _CRS starting from zero.
      pin - Pin in the GpioIo()/GpioInt() resource. Typically this is zero.
      active_low - If 1 the GPIO is marked as active_low.
    Since ACPI GpioIo() resource does not have field saying whether it is
    active low or high, the "active_low" argument can be used here. Setting
    it to 1 marks the GPIO as active low.
    In our Bluetooth example the "reset-gpio" refers to the second GpioIo()
    resource, second pin in that resource with the GPIO number of 31.
    This patch implements necessary support to gpiolib for extracting GPIOs
    using _DSD device properties.
    Signed-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Acked-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    Acked-by: default avatarGrant Likely <grant.likely@linaro.org>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
gpiolib.h 4.65 KB