ARM: tegra: Add DT binding for Tegra186 GPIO controllers

Tegra186 contains two separate but mostly similar GPIO controllers.
Register layout differs significantly from previous Tegra generations,
and so a new binding is required to describe them in device tree. This
patch adds that binding.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/gpio/nvidia,tegra186-gpio.txt

+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 <dt-bindings/gpio/tegra186-gpio.h>
+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.
+
+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.
+    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 <dt-bindings/gpio/tegra186-gpio.h>.
+    - 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 <dt-bindings/gpio/tegra186-gpio.h>.
+    - 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.
+
+Example:
+
+#include <dt-bindings/interrupt-controller/irq.h>
+
+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>;
+};

include/dt-bindings/gpio/tegra186-gpio.h

+/*
+ * This header provides constants for binding nvidia,tegra186-gpio*.
+ *
+ * The first cell in Tegra's GPIO specifier is the GPIO ID. The macros below
+ * provide names for this.
+ *
+ * The second cell contains standard flag values specified in gpio.h.
+ */
+
+#ifndef _DT_BINDINGS_GPIO_TEGRA_GPIO_H
+#define _DT_BINDINGS_GPIO_TEGRA_GPIO_H
+
+#include <dt-bindings/gpio/gpio.h>
+
+/* GPIOs implemented by main GPIO controller */
+#define TEGRA_MAIN_GPIO_PORT_A 0
+#define TEGRA_MAIN_GPIO_PORT_B 1
+#define TEGRA_MAIN_GPIO_PORT_C 2
+#define TEGRA_MAIN_GPIO_PORT_D 3
+#define TEGRA_MAIN_GPIO_PORT_E 4
+#define TEGRA_MAIN_GPIO_PORT_F 5
+#define TEGRA_MAIN_GPIO_PORT_G 6
+#define TEGRA_MAIN_GPIO_PORT_H 7
+#define TEGRA_MAIN_GPIO_PORT_I 8
+#define TEGRA_MAIN_GPIO_PORT_J 9
+#define TEGRA_MAIN_GPIO_PORT_K 10
+#define TEGRA_MAIN_GPIO_PORT_L 11
+#define TEGRA_MAIN_GPIO_PORT_M 12
+#define TEGRA_MAIN_GPIO_PORT_N 13
+#define TEGRA_MAIN_GPIO_PORT_O 14
+#define TEGRA_MAIN_GPIO_PORT_P 15
+#define TEGRA_MAIN_GPIO_PORT_Q 16
+#define TEGRA_MAIN_GPIO_PORT_R 17
+#define TEGRA_MAIN_GPIO_PORT_T 18
+#define TEGRA_MAIN_GPIO_PORT_X 19
+#define TEGRA_MAIN_GPIO_PORT_Y 20
+#define TEGRA_MAIN_GPIO_PORT_BB 21
+#define TEGRA_MAIN_GPIO_PORT_CC 22
+
+#define TEGRA_MAIN_GPIO(port, offset) \
+	((TEGRA_MAIN_GPIO_PORT_##port * 8) + offset)
+
+/* GPIOs implemented by AON GPIO controller */
+#define TEGRA_AON_GPIO_PORT_S 0
+#define TEGRA_AON_GPIO_PORT_U 1
+#define TEGRA_AON_GPIO_PORT_V 2
+#define TEGRA_AON_GPIO_PORT_W 3
+#define TEGRA_AON_GPIO_PORT_Z 4
+#define TEGRA_AON_GPIO_PORT_AA 5
+#define TEGRA_AON_GPIO_PORT_EE 6
+#define TEGRA_AON_GPIO_PORT_FF 7
+
+#define TEGRA_AON_GPIO(port, offset) \
+	((TEGRA_AON_GPIO_PORT_##port * 8) + offset)
+
+#endif