Re: [PATCH 06/13] gpio / ACPI: Add support for _DSD device properties

Mika Westerberg
2014-10-15T08:46:20Z

On Tue, Oct 14, 2014 at 03:44:03PM +0200, Grant Likely wrote:
> On Tue, 07 Oct 2014 02:15:18 +0200
> , "Rafael J. Wysocki" <rjw@rjwysocki.net>
> wrote:
> > From: Mika Westerberg <mika.westerberg@linux.intel.com>
> >
> > 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.
>
> Patch looks good, but please put the above description into
> /Documentation until we've got a better place to document extra bindings.

Thanks for the review.

If you don't mind, I would like to make a separate patch on top of this
series adding this description to Documentation/acpi/properties.txt.