On 27/11/19 2:12 PM, Geert Uytterhoeven wrote: > Add Device Tree bindings for a GPIO repeater, with optional translation > of physical signal properties. This is useful for describing explicitly > the presence of e.g. an inverter on a GPIO line, and was inspired by the > non-YAML gpio-inverter bindings by Harish Jenny K N > <harish_kandiga@xxxxxxxxxx>[1]. > > Note that this is different from a GPIO Nexus Node[2], which cannot do > physical signal property translation. > > While an inverter can be described implicitly by exchanging the > GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags, this has its limitations. > Each GPIO line has only a single GPIO_ACTIVE_* flag, but applies to both > th provider and consumer sides: > 1. The GPIO provider (controller) looks at the flags to know the > polarity, so it can translate between logical (active/not active) > and physical (high/low) signal levels. > 2. While the signal polarity is usually fixed on the GPIO consumer > side (e.g. an LED is tied to either the supply voltage or GND), > it may be configurable on some devices, and both sides need to > agree. Hence the GPIO_ACTIVE_* flag as seen by the consumer must > match the actual polarity. > There exists a similar issue with interrupt flags, where both the > interrupt controller and the device generating the interrupt need > to agree, which breaks in the presence of a physical inverter not > described in DT (see e.g. [3]). > > [1] "[PATCH V4 2/2] gpio: inverter: document the inverter bindings" > https://lore.kernel.org/linux-gpio/1561699236-18620-3-git-send-email-harish_kandiga@xxxxxxxxxx/ > > [2] Devicetree Specification v0.3-rc2, Section 2.5 > https://github.com/devicetree-org/devicetree-specification/releases/tag/v0.3-rc2 > > [3] "[PATCH] wlcore/wl18xx: Add invert-irq OF property for physically > inverted IRQ" > https://lore.kernel.org/linux-renesas-soc/20190607172958.20745-1-erosca@xxxxxxxxxxxxxx/ > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > --- > v3: > - New. > --- > .../bindings/gpio/gpio-repeater.yaml | 53 +++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/devicetree/bindings/gpio/gpio-repeater.yaml > > diff --git a/Documentation/devicetree/bindings/gpio/gpio-repeater.yaml b/Documentation/devicetree/bindings/gpio/gpio-repeater.yaml > new file mode 100644 > index 0000000000000000..efdee0c3be43f731 > --- /dev/null > +++ b/Documentation/devicetree/bindings/gpio/gpio-repeater.yaml > @@ -0,0 +1,53 @@ > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/gpio/gpio-repeater.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: GPIO Repeater > + > +maintainers: > + - Harish Jenny K N <harish_kandiga@xxxxxxxxxx> > + - Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > + > +description: > + This represents a repeater for one or more GPIOs, possibly including physical > + signal property translation (e.g. polarity inversion). > + > +properties: > + compatible: > + const: gpio-repeater > + > + "#gpio-cells": > + const: 2 > + > + gpio-controller: true > + > + gpios: > + description: > + Phandle and specifier, one for each repeated GPIO. > + > + gpio-line-names: > + description: > + Strings defining the names of the GPIO lines going out of the GPIO > + controller. > + > +required: > + - compatible > + - "#gpio-cells" > + - gpio-controller > + - gpios > + > +additionalProperties: false > + > +examples: > + # Device node describing a polarity inverter for a single GPIO > + - | > + #include <dt-bindings/gpio/gpio.h> > + > + inverter: gpio-repeater { > + compatible = "gpio-repeater"; > + #gpio-cells = <2>; > + gpio-controller; > + gpios = <&gpio 95 GPIO_ACTIVE_LOW>; > + }; just a suggestion: giving a gpio-line-names in the example would look useful.
