Re: [RFC PATCH v2 06/16] gpio / ACPI: Add support for _DSD device properties

Linus Walleij
2014-09-23T15:27:20Z

On Tue, Sep 16, 2014 at 1:52 PM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:

> 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>

If Rafael is happy with this approach, and you decide to take it
through the ACPI tree.

Yours,
Linus Walleij