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author | Mika Westerberg <mika.westerberg@linux.intel.com> | 2014-10-29 15:41:01 +0100 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-11-04 21:58:22 +0100 |
commit | 0d9a693cc8619b28f0eeb689a554647d42848fde (patch) | |
tree | a5df01e1767f6a537531ad5bfc69cb9b2097bdf6 /Documentation | |
parent | f60e7074902a66d9a132a971ecda63ee5b8bc154 (diff) | |
download | linux-stable-0d9a693cc8619b28f0eeb689a554647d42848fde.tar.gz linux-stable-0d9a693cc8619b28f0eeb689a554647d42848fde.tar.bz2 linux-stable-0d9a693cc8619b28f0eeb689a554647d42848fde.zip |
gpio / ACPI: Add support for _DSD device properties
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 ()
{
ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/acpi/gpio-properties.txt | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/acpi/gpio-properties.txt b/Documentation/acpi/gpio-properties.txt new file mode 100644 index 000000000000..3e45b8b7e4f2 --- /dev/null +++ b/Documentation/acpi/gpio-properties.txt @@ -0,0 +1,52 @@ +_DSD Device Properties Related to GPIO +-------------------------------------- + +With the release of ACPI 5.1 and the _DSD configuration objecte names +can finally be given to GPIOs (and other things as well) returned by +_CRS. Previously, we were only able to use an integer index to find +the corresponding GPIO, which is pretty error prone (it depends on +the _CRS output ordering, for example). + +With _DSD we can now query GPIOs using a name instead of an integer +index, like the ASL example below 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 () + { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + 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 a 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. |