NVIDIA Tegra186 GPIO controllers Tegra186 contains two GPIO controllers; a main controller and an "AON" controller. This binding document applies to both controllers. The register layouts for the controllers share many similarities, but also some significant differences. Hence, this document describes closely related but different bindings and compatible values. The Tegra186 GPIO controller allows software to set the IO direction of, and read/write the value of, numerous GPIO signals. Routing of GPIO signals to package balls is under the control of a separate pin controller HW block. Two major sets of registers exist: a) Security registers, which allow configuration of allowed access to the GPIO register set. These registers exist in a single contiguous block of physical address space. The size of this block, and the security features available, varies between the different GPIO controllers. Access to this set of registers is not necessary in all circumstances. Code that wishes to configure access to the GPIO registers needs access to these registers to do so. Code which simply wishes to read or write GPIO data does not need access to these registers. b) GPIO registers, which allow manipulation of the GPIO signals. In some GPIO controllers, these registers are exposed via multiple "physical aliases" in address space, each of which access the same underlying state. See the hardware documentation for rationale. Any particular GPIO client is expected to access just one of these physical aliases. Tegra HW documentation describes a unified naming convention for all GPIOs implemented by the SoC. Each GPIO is assigned to a port, and a port may control a number of GPIOs. Thus, each GPIO is named according to an alphabetical port name and an integer GPIO name within the port. For example, GPIO_PA0, GPIO_PN6, or GPIO_PCC3. The number of ports implemented by each GPIO controller varies. The number of implemented GPIOs within each port varies. GPIO registers within a controller are grouped and laid out according to the port they affect. The mapping from port name to the GPIO controller that implements that port, and the mapping from port name to register offset within a controller, are both extremely non-linear. The header file describes the port-level mapping. In that file, the naming convention for ports matches the HW documentation. The values chosen for the names are alphabetically sorted within a particular controller. Drivers need to map between the DT GPIO IDs and HW register offsets using a lookup table. Each GPIO controller can generate a number of interrupt signals. Each signal represents the aggregate status for all GPIOs within a set of ports. Thus, the number of interrupt signals generated by a controller varies as a rough function of the number of ports it implements. Note that the HW documentation refers to both the overall controller HW module and the sets-of-ports as "controllers". Each GPIO controller in fact generates multiple interrupts signals for each set of ports. Each GPIO may be configured to feed into a specific one of the interrupt signals generated by a set-of-ports. The intent is for each generated signal to be routed to a different CPU, thus allowing different CPUs to each handle subsets of the interrupts within a port. The status of each of these per-port-set signals is reported via a separate register. Thus, a driver needs to know which status register to observe. This binding currently defines no configuration mechanism for this. By default, drivers should use register GPIO_${port}_INTERRUPT_STATUS_G1_0. Future revisions to the binding could define a property to configure this. Tegra186 has separate HW block called GTE block (GPIO Timestamping Engine), which can be used to capture the TSC timestamp based on gpio interrupts or events. Functionality of this block is also exposed via GPIO driver. We need to specify "use-timestamp" field in the GPIO DT block in order to enable this feature. Along with above boolean field, we also need to specify new register block "gte" which will be used to configure GTE. Required properties: - compatible Array of strings. One of: - "nvidia,tegra186-gpio". - "nvidia,tegra186-gpio-aon". - reg-names Array of strings. Contains a list of names for the register spaces described by the reg property. May contain the following entries, in any order: - "gpio": Mandatory. GPIO control registers. This may cover either: a) The single physical alias that this OS should use. b) All physical aliases that exist in the controller. This is appropriate when the OS is responsible for managing assignment of the physical aliases. - "security": Optional. Security configuration registers. - "gte": Needed if one wants to use GTE for timestamping Users of this binding MUST look up entries in the reg property by name, using this reg-names property to do so. - reg Array of (physical base address, length) tuples. Must contain one entry per entry in the reg-names property, in a matching order. - interrupts Array of interrupt specifiers. The interrupt outputs from the HW block, one per set of ports, in the order the HW manual describes them. The number of entries required varies depending on compatible value: - "nvidia,tegra186-gpio": 6 entries. - "nvidia,tegra186-gpio-aon": 1 entry. - gpio-controller Boolean. Marks the device node as a GPIO controller/provider. - #gpio-cells Single-cell integer. Must be <2>. Indicates how many cells are used in a consumer's GPIO specifier. In the specifier: - The first cell is the pin number. See . - The second cell contains flags: - Bit 0 specifies polarity - 0: Active-high (normal). - 1: Active-low (inverted). - interrupt-controller Boolean. Marks the device node as an interrupt controller/provider. - #interrupt-cells Single-cell integer. Must be <2>. Indicates how many cells are used in a consumer's interrupt specifier. In the specifier: - The first cell is the GPIO number. See . - The second cell is contains flags: - Bits [3:0] indicate trigger type and level: - 1: Low-to-high edge triggered. - 2: High-to-low edge triggered. - 4: Active high level-sensitive. - 8: Active low level-sensitive. Valid combinations are 1, 2, 3, 4, 8. - use-timestamp If one wants to use the GTE block for timestamping. Example: #include gpio@2200000 { compatible = "nvidia,tegra186-gpio"; reg-names = "security", "gpio"; reg = <0x0 0x2200000 0x0 0x10000>, <0x0 0x2210000 0x0 0x10000>; interrupts = <0 47 IRQ_TYPE_LEVEL_HIGH>, <0 50 IRQ_TYPE_LEVEL_HIGH>, <0 53 IRQ_TYPE_LEVEL_HIGH>, <0 56 IRQ_TYPE_LEVEL_HIGH>, <0 59 IRQ_TYPE_LEVEL_HIGH>, <0 180 IRQ_TYPE_LEVEL_HIGH>; gpio-controller; #gpio-cells = <2>; interrupt-controller; #interrupt-cells = <2>; }; gpio@c2f0000 { compatible = "nvidia,tegra186-gpio-aon"; reg-names = "security", "gpio"; reg = <0x0 0xc2f0000 0x0 0x1000>, <0x0 0xc2f1000 0x0 0x1000>; interrupts = <0 60 IRQ_TYPE_LEVEL_HIGH>; gpio-controller; #gpio-cells = <2>; interrupt-controller; #interrupt-cells = <2>; }; With GTE enabled: gpio@c2f0000 { compatible = "nvidia,tegra186-gpio-aon"; reg-names = "security", "gpio", "gte"; reg = <0x0 0xc2f0000 0x0 0x1000>, <0x0 0xc2f1000 0x0 0x1000>, <0x0 0xc1e0000 0x0 0x10000>; interrupts = <0 60 IRQ_TYPE_LEVEL_HIGH>; gpio-controller; #gpio-cells = <2>; interrupt-controller; #interrupt-cells = <2>; use-timestamp; };