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| -rw-r--r-- | Documentation/devicetree/bindings/gpio/gpio.txt | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index 069cdf6f9dac..f509ecf03ece 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -131,6 +131,19 @@ Every GPIO controller node must contain both an empty "gpio-controller" property, and a #gpio-cells integer property, which indicates the number of cells in a gpio-specifier. +Some system-on-chips (SoCs) use the concept of GPIO banks. A GPIO bank is an +instance of a hardware IP core on a silicon die, usually exposed to the +programmer as a coherent range of I/O addresses. Usually each such bank is +exposed in the device tree as an individual gpio-controller node, reflecting +the fact that the hardware was synthesized by reusing the same IP block a +few times over. + +A GPIO controller may specify a bank ID. This is a hardware index that +indicate the logical order of the GPIO controller in the hardware architecture, +usually in the sequence 0, 1, 2 .. n. The hardware index may be different +from the order of register ranges and related to the backplane of how this +one bank is connected to the outside through a pin controller for example. + Optionally, a GPIO controller may have a "ngpios" property. This property indicates the number of in-use slots of available slots for GPIOs. The typical example is something like this: the hardware register is 32 bits @@ -152,6 +165,7 @@ gpio-controller@00000000 { reg = <0x00000000 0x1000>; gpio-controller; #gpio-cells = <2>; + gpio-bank = <0>; ngpios = <18>; } |