From 69d301fdd19635a39cb2b78e53fdd625b7a27924 Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Thu, 24 Sep 2015 15:05:45 -0700 Subject: gpio: add DT bindings for existing consumer flags It is customary for GPIO controllers to support open drain/collector and open source/emitter configurations. Add standard GPIO line flags to account for this and augment the documentation to say that these are the most generic bindings. Several people approached me to add new flags to the lines, and this makes sense, but let's first bind up the most common cases before we start to add exotic stuff. Thanks to H. Nikolaus Schaller for ideas on how to encode single-ended wiring such as open drain/source and open collector/emitter. Cc: Tony Lindgren Cc: Grygorii Strashko Cc: H. Nikolaus Schaller Signed-off-by: Linus Walleij --- Documentation/devicetree/bindings/gpio/gpio.txt | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'Documentation/devicetree/bindings/gpio/gpio.txt') diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index 5788d5cf1252..63b1b9039ce8 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -52,9 +52,13 @@ only uses one. gpio-specifier may encode: bank, pin position inside the bank, whether pin is open-drain and whether pin is logically inverted. + Exact meaning of each specifier cell is controller specific, and must -be documented in the device tree binding for the device. Use the macros -defined in include/dt-bindings/gpio/gpio.h whenever possible: +be documented in the device tree binding for the device. + +Most controllers are however specifying a generic flag bitfield +in the last cell, so for these, use the macros defined in +include/dt-bindings/gpio/gpio.h whenever possible: Example of a node using GPIOs: @@ -65,6 +69,15 @@ Example of a node using GPIOs: GPIO_ACTIVE_HIGH is 0, so in this example gpio-specifier is "18 0" and encodes GPIO pin number, and GPIO flags as accepted by the "qe_pio_e" gpio-controller. +Optional standard bitfield specifiers for the last cell: + +- Bit 0: 0 means active high, 1 means active low +- Bit 1: 1 means single-ended wiring, see: + https://en.wikipedia.org/wiki/Single-ended_triode + When used with active-low, this means open drain/collector, see: + https://en.wikipedia.org/wiki/Open_collector + When used with active-high, this means open source/emitter + 1.1) GPIO specifier best practices ---------------------------------- -- cgit v1.2.3 From aacaffd1d9a6f8e2c7369d83c21d41c3b53e2edc Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Fri, 30 Oct 2015 11:58:28 +0100 Subject: gpio: dt-bindings: document the official use of "ngpios" There are a bunch of drivers that utilize the "ngpios" DT property without any vendor prefix. Try to start cleaning up the mess by defining what we mean by this property. Cc: devicetree@vger.kernel.org Cc: Pramod Kumar Cc: Jonas Gorski Signed-off-by: Linus Walleij --- Documentation/devicetree/bindings/gpio/gpio.txt | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) (limited to 'Documentation/devicetree/bindings/gpio/gpio.txt') diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index 63b1b9039ce8..e9c49dc4e895 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -129,6 +129,30 @@ 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. +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 +wide, but only 18 of the bits have a physical counterpart. The driver is +generally written so that all 32 bits can be used, but the IP block is reused +in a lot of designs, some using all 32 bits, some using 18 and some using +12. In this case, setting "ngpios = <18>;" informs the driver that only the +first 18 GPIOs, at local offset 0 .. 17, are in use. + +If these GPIOs do not happen to be the first N GPIOs at offset 0...N-1, an +additional bitmask is needed to specify which GPIOs are actually in use, +and which are dummies. The bindings for this case has not yet been +specified, but should be specified if/when such hardware appears. + +Example: + +gpio-controller@00000000 { + compatible = "foo"; + reg = <0x00000000 0x1000>; + gpio-controller; + #gpio-cells = <2>; + ngpios = <18>; +} + The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism providing automatic GPIO request and configuration as part of the gpio-controller's driver probe function. -- cgit v1.2.3