Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 348 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
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+Specifying GPIO information for devices
+=======================================
+
+1) gpios property
+-----------------
+
+GPIO properties should be named "[<name>-]gpios", with <name> being the purpose
+of this GPIO for the device. While a non-existent <name> is considered valid
+for compatibility reasons (resolving to the "gpios" property), it is not allowed
+for new bindings. Also, GPIO properties named "[<name>-]gpio" are valid and old
+bindings use it, but are only supported for compatibility reasons and should not
+be used for newer bindings since it has been deprecated.
+
+GPIO properties can contain one or more GPIO phandles, but only in exceptional
+cases should they contain more than one. If your device uses several GPIOs with
+distinct functions, reference each of them under its own property, giving it a
+meaningful name. The only case where an array of GPIOs is accepted is when
+several GPIOs serve the same function (e.g. a parallel data line).
+
+The exact purpose of each gpios property must be documented in the device tree
+binding of the device.
+
+The following example could be used to describe GPIO pins used as device enable
+and bit-banged data signals:
+
+	gpio1: gpio1 {
+		gpio-controller;
+		#gpio-cells = <2>;
+	};
+	[...]
+
+	data-gpios = <&gpio1 12 0>,
+		     <&gpio1 13 0>,
+		     <&gpio1 14 0>,
+		     <&gpio1 15 0>;
+
+In the above example, &gpio1 uses 2 cells to specify a gpio. The first cell is
+a local offset to the GPIO line and the second cell represent consumer flags,
+such as if the consumer desire the line to be active low (inverted) or open
+drain. This is the recommended practice.
+
+The exact meaning of each specifier cell is controller specific, and must be
+documented in the device tree binding for the device, but it is strongly
+recommended to use the two-cell approach.
+
+Most controllers are 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:
+
+	node {
+		enable-gpios = <&qe_pio_e 18 GPIO_ACTIVE_HIGH>;
+	};
+
+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: 0 mean push-pull wiring, see:
+           https://en.wikipedia.org/wiki/Push-pull_output
+         1 means single-ended wiring, see:
+           https://en.wikipedia.org/wiki/Single-ended_triode
+- Bit 2: 0 means open-source, 1 means open drain, see:
+           https://en.wikipedia.org/wiki/Open_collector
+- Bit 3: 0 means the output should be maintained during sleep/low-power mode
+         1 means the output state can be lost during sleep/low-power mode
+- Bit 4: 0 means no pull-up resistor should be enabled
+         1 means a pull-up resistor should be enabled
+         This setting only applies to hardware with a simple on/off
+         control for pull-up configuration. If the hardware has more
+         elaborate pull-up configuration, it should be represented
+         using a pin control binding.
+- Bit 5: 0 means no pull-down resistor should be enabled
+         1 means a pull-down resistor should be enabled
+         This setting only applies to hardware with a simple on/off
+         control for pull-down configuration. If the hardware has more
+         elaborate pull-down configuration, it should be represented
+         using a pin control binding.
+
+1.1) GPIO specifier best practices
+----------------------------------
+
+A gpio-specifier should contain a flag indicating the GPIO polarity; active-
+high or active-low. If it does, the following best practices should be
+followed:
+
+The gpio-specifier's polarity flag should represent the physical level at the
+GPIO controller that achieves (or represents, for inputs) a logically asserted
+value at the device. The exact definition of logically asserted should be
+defined by the binding for the device. If the board inverts the signal between
+the GPIO controller and the device, then the gpio-specifier will represent the
+opposite physical level than the signal at the device's pin.
+
+When the device's signal polarity is configurable, the binding for the
+device must either:
+
+a) Define a single static polarity for the signal, with the expectation that
+any software using that binding would statically program the device to use
+that signal polarity.
+
+The static choice of polarity may be either:
+
+a1) (Preferred) Dictated by a binding-specific DT property.
+
+or:
+
+a2) Defined statically by the DT binding itself.
+
+In particular, the polarity cannot be derived from the gpio-specifier, since
+that would prevent the DT from separately representing the two orthogonal
+concepts of configurable signal polarity in the device, and possible board-
+level signal inversion.
+
+or:
+
+b) Pick a single option for device signal polarity, and document this choice
+in the binding. The gpio-specifier should represent the polarity of the signal
+(at the GPIO controller) assuming that the device is configured for this
+particular signal polarity choice. If software chooses to program the device
+to generate or receive a signal of the opposite polarity, software will be
+responsible for correctly interpreting (inverting) the GPIO signal at the GPIO
+controller.
+
+2) gpio-controller nodes
+------------------------
+
+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.
+
+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 set of tuples is needed to specify which GPIOs are unusable, with
+the gpio-reserved-ranges binding. This property indicates the start and size
+of the GPIOs that can't be used.
+
+Optionally, a GPIO controller may have a "gpio-line-names" property. This is
+an array of strings defining the names of the GPIO lines going out of the
+GPIO controller.
+
+For lines which are routed to on-board devices, this name should be
+the most meaningful producer name for the system, such as a rail name
+indicating the usage. Package names, such as a pin name, are discouraged:
+such lines have opaque names (since they are by definition general-purpose)
+and such names are usually not very helpful. For example "MMC-CD", "Red LED
+Vdd" and "ethernet reset" are reasonable line names as they describe what
+the line is used for. "GPIO0" is not a good name to give to a GPIO line
+that is hard-wired to a specific device.
+
+However, in the case of lines that are routed to a general purpose header
+(e.g. the Raspberry Pi 40-pin header), and therefore are not hard-wired to
+specific devices, using a pin number or the names on the header is fine
+provided these are real (preferably unique) names. Using an SoC's pad name
+or package name, or names made up from kernel-internal software constructs,
+are strongly discouraged. For example "pin8 [gpio14/uart0_txd]" is fine
+if the board's documentation labels pin 8 as such. However "PortB_24" (an
+example of a name from an SoC's reference manual) would not be desirable.
+
+In either case placeholders are discouraged: rather use the "" (blank
+string) if the use of the GPIO line is undefined in your design. Ideally,
+try to add comments to the dts file describing the naming the convention
+you have chosen, and specifying from where the names are derived.
+
+The names are assigned starting from line offset 0, from left to right,
+from the passed array. An incomplete array (where the number of passed
+names is less than ngpios) will be used up until the last provided valid
+line index.
+
+Example:
+
+gpio-controller@00000000 {
+	compatible = "foo";
+	reg = <0x00000000 0x1000>;
+	gpio-controller;
+	#gpio-cells = <2>;
+	ngpios = <18>;
+	gpio-reserved-ranges = <0 4>, <12 2>;
+	gpio-line-names = "MMC-CD", "MMC-WP", "VDD eth", "RST eth", "LED R",
+		"LED G", "LED B", "Col A", "Col B", "Col C", "Col D",
+		"Row A", "Row B", "Row C", "Row D", "NMI button",
+		"poweroff", "reset";
+}
+
+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.
+
+Each GPIO hog definition is represented as a child node of the GPIO controller.
+Required properties:
+- gpio-hog:   A property specifying that this child node represents a GPIO hog.
+- gpios:      Store the GPIO information (id, flags, ...) for each GPIO to
+	      affect. Shall contain an integer multiple of the number of cells
+	      specified in its parent node (GPIO controller node).
+Only one of the following properties scanned in the order shown below.
+This means that when multiple properties are present they will be searched
+in the order presented below and the first match is taken as the intended
+configuration.
+- input:      A property specifying to set the GPIO direction as input.
+- output-low  A property specifying to set the GPIO direction as output with
+	      the value low.
+- output-high A property specifying to set the GPIO direction as output with
+	      the value high.
+
+Optional properties:
+- line-name:  The GPIO label name. If not present the node name is used.
+
+Example of two SOC GPIO banks defined as gpio-controller nodes:
+
+	qe_pio_a: gpio-controller@1400 {
+		compatible = "fsl,qe-pario-bank-a", "fsl,qe-pario-bank";
+		reg = <0x1400 0x18>;
+		gpio-controller;
+		#gpio-cells = <2>;
+
+		line_b-hog {
+			gpio-hog;
+			gpios = <6 0>;
+			output-low;
+			line-name = "foo-bar-gpio";
+		};
+	};
+
+	qe_pio_e: gpio-controller@1460 {
+		compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
+		reg = <0x1460 0x18>;
+		gpio-controller;
+		#gpio-cells = <2>;
+	};
+
+2.1) gpio- and pin-controller interaction
+-----------------------------------------
+
+Some or all of the GPIOs provided by a GPIO controller may be routed to pins
+on the package via a pin controller. This allows muxing those pins between
+GPIO and other functions. It is a fairly common practice among silicon
+engineers.
+
+2.2) Ordinary (numerical) GPIO ranges
+-------------------------------------
+
+It is useful to represent which GPIOs correspond to which pins on which pin
+controllers. The gpio-ranges property described below represents this with
+a discrete set of ranges mapping pins from the pin controller local number space
+to pins in the GPIO controller local number space.
+
+The format is: <[pin controller phandle], [GPIO controller offset],
+                [pin controller offset], [number of pins]>;
+
+The GPIO controller offset pertains to the GPIO controller node containing the
+range definition.
+
+The pin controller node referenced by the phandle must conform to the bindings
+described in pinctrl/pinctrl-bindings.txt.
+
+Each offset runs from 0 to N. It is perfectly fine to pile any number of
+ranges with just one pin-to-GPIO line mapping if the ranges are concocted, but
+in practice these ranges are often lumped in discrete sets.
+
+Example:
+
+    gpio-ranges = <&foo 0 20 10>, <&bar 10 50 20>;
+
+This means:
+- pins 20..29 on pin controller "foo" is mapped to GPIO line 0..9 and
+- pins 50..69 on pin controller "bar" is mapped to GPIO line 10..29
+
+
+Verbose example:
+
+	qe_pio_e: gpio-controller@1460 {
+		#gpio-cells = <2>;
+		compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
+		reg = <0x1460 0x18>;
+		gpio-controller;
+		gpio-ranges = <&pinctrl1 0 20 10>, <&pinctrl2 10 50 20>;
+	};
+
+Here, a single GPIO controller has GPIOs 0..9 routed to pin controller
+pinctrl1's pins 20..29, and GPIOs 10..29 routed to pin controller pinctrl2's
+pins 50..69.
+
+
+2.3) GPIO ranges from named pin groups
+--------------------------------------
+
+It is also possible to use pin groups for gpio ranges when pin groups are the
+easiest and most convenient mapping.
+
+Both both <pinctrl-base> and <count> must set to 0 when using named pin groups
+names.
+
+The property gpio-ranges-group-names must contain exactly one string for each
+range.
+
+Elements of gpio-ranges-group-names must contain the name of a pin group
+defined in the respective pin controller. The number of pins/GPIO lines in the
+range is the number of pins in that pin group. The number of pins of that
+group is defined int the implementation and not in the device tree.
+
+If numerical and named pin groups are mixed, the string corresponding to a
+numerical pin range in gpio-ranges-group-names must be empty.
+
+Example:
+
+	gpio_pio_i: gpio-controller@14b0 {
+		#gpio-cells = <2>;
+		compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
+		reg = <0x1480 0x18>;
+		gpio-controller;
+		gpio-ranges =			<&pinctrl1 0 20 10>,
+						<&pinctrl2 10 0 0>,
+						<&pinctrl1 15 0 10>,
+						<&pinctrl2 25 0 0>;
+		gpio-ranges-group-names =	"",
+						"foo",
+						"",
+						"bar";
+	};
+
+Here, three GPIO ranges are defined referring to two pin controllers.
+
+pinctrl1 GPIO ranges are defined using pin numbers whereas the GPIO ranges
+in pinctrl2 are defined using the pin groups named "foo" and "bar".
+
+Previous versions of this binding required all pin controller nodes that
+were referenced by any gpio-ranges property to contain a property named
+#gpio-range-cells with value <3>. This requirement is now deprecated.
+However, that property may still exist in older device trees for
+compatibility reasons, and would still be required even in new device
+trees that need to be compatible with older software.