dt-bindings: pinctrl: Add DT bindings for Spreadtrum SC9860

This patch adds the binding documentation for Spreadtrum SC9860 pin
controller device.
Signed-off-by: Baolin Wang <baolin.wang@spreadtrum.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt

+* Spreadtrum Pin Controller
+
+The Spreadtrum pin controller are organized in 3 blocks (types).
+
+The first block comprises some global control registers, and each
+register contains several bit fields with one bit or several bits
+to configure for some global common configuration, such as domain
+pad driving level, system control select and so on ("domain pad
+driving level": One pin can output 3.0v or 1.8v, depending on the
+related domain pad driving selection, if the related domain pad
+slect 3.0v, then the pin can output 3.0v. "system control" is used
+to choose one function (like: UART0) for which system, since we
+have several systems (AP/CP/CM4) on one SoC.).
+
+There are too much various configuration that we can not list all
+of them, so we can not make every Spreadtrum-special configuration
+as one generic configuration, and maybe it will add more strange
+global configuration in future. Then we add one "sprd,control" to
+set these various global control configuration, and we need use
+magic number for this property.
+
+Moreover we recognise every fields comprising one bit or several
+bits in one global control register as one pin, thus we should
+record every pin's bit offset, bit width and register offset to
+configure this field (pin).
+
+The second block comprises some common registers which have unified
+register definition, and each register described one pin is used
+to configure the pin sleep mode, function select and sleep related
+configuration.
+
+Now we have 4 systems for sleep mode on SC9860 SoC: AP system,
+PUBCP system, TGLDSP system and AGDSP system. And the pin sleep
+related configuration are:
+- input-enable
+- input-disable
+- output-high
+- output-low
+- bias-pull-up
+- bias-pull-down
+
+In some situation we need set the pin sleep mode and pin sleep related
+configuration, to set the pin sleep related configuration automatically
+by hardware when the system specified by sleep mode goes into deep
+sleep mode. For example, if we set the pin sleep mode as PUBCP_SLEEP
+and set the pin sleep related configuration as "input-enable", which
+means when PUBCP system goes into deep sleep mode, this pin will be set
+input enable automatically.
+
+Moreover we can not use the "sleep" state, since some systems (like:
+PUBCP system) do not run linux kernel OS (only AP system run linux
+kernel on SC9860 platform), then we can not select "sleep" state
+when the PUBCP system goes into deep sleep mode. Thus we introduce
+"sprd,sleep-mode" property to set pin sleep mode.
+
+The last block comprises some misc registers which also have unified
+register definition, and each register described one pin is used to
+configure drive strength, pull up/down and so on. Especially for pull
+up, we have two kind pull up resistor: 20K and 4.7K.
+
+Required properties for Spreadtrum pin controller:
+- compatible: "sprd,<soc>-pinctrl"
+  Please refer to each sprd,<soc>-pinctrl.txt binding doc for supported SoCs.
+- reg: The register address of pin controller device.
+- pins : An array of pin names.
+
+Optional properties:
+- function: Specified the function name.
+- drive-strength: Drive strength in mA.
+- input-schmitt-disable: Enable schmitt-trigger mode.
+- input-schmitt-enable: Disable schmitt-trigger mode.
+- bias-disable: Disable pin bias.
+- bias-pull-down: Pull down on pin.
+- bias-pull-up: Pull up on pin.
+- input-enable: Enable pin input.
+- input-disable: Enable pin output.
+- output-high: Set the pin as an output level high.
+- output-low: Set the pin as an output level low.
+- sleep-hardware-state: Indicate these configs in this state are sleep related.
+- sprd,control: Control values referring to databook for global control pins.
+- sprd,sleep-mode: Sleep mode selection.
+
+Please refer to each sprd,<soc>-pinctrl.txt binding doc for supported values.

Documentation/devicetree/bindings/pinctrl/sprd,sc9860-pinctrl.txt

+* Spreadtrum SC9860 Pin Controller
+
+Please refer to sprd,pinctrl.txt in this directory for common binding part
+and usage.
+
+Required properties:
+- compatible: Must be "sprd,sc9860-pinctrl".
+- reg: The register address of pin controller device.
+- pins : An array of strings, each string containing the name of a pin.
+
+Optional properties:
+- function: A string containing the name of the function, values must be
+  one of: "func1", "func2", "func3" and "func4".
+- drive-strength: Drive strength in mA. Supported values: 2, 4, 6, 8, 10,
+  12, 14, 16, 20, 21, 24, 25, 27, 29, 31 and 33.
+- input-schmitt-disable: Enable schmitt-trigger mode.
+- input-schmitt-enable: Disable schmitt-trigger mode.
+- bias-disable: Disable pin bias.
+- bias-pull-down: Pull down on pin.
+- bias-pull-up: Pull up on pin. Supported values: 20000 for pull-up resistor
+  is 20K and 4700 for pull-up resistor is 4.7K.
+- input-enable: Enable pin input.
+- input-disable: Enable pin output.
+- output-high: Set the pin as an output level high.
+- output-low: Set the pin as an output level low.
+- sleep-hardware-state: Indicate these configs in this state are sleep related.
+- sprd,control: Control values referring to databook for global control pins.
+- sprd,sleep-mode: Choose the pin sleep mode, and supported values are:
+  AP_SLEEP, PUBCP_SLEEP, TGLDSP_SLEEP and AGDSP_SLEEP.
+
+Pin sleep mode definition:
+enum pin_sleep_mode {
+	AP_SLEEP = BIT(0),
+	PUBCP_SLEEP = BIT(1),
+	TGLDSP_SLEEP = BIT(2),
+	AGDSP_SLEEP = BIT(3),
+};
+
+Example:
+pin_controller: pinctrl@402a0000 {
+	compatible = "sprd,sc9860-pinctrl";
+	reg = <0x402a0000 0x10000>;
+
+	grp1: sd0 {
+		pins = "SC9860_VIO_SD2_IRTE", "SC9860_VIO_SD0_IRTE";
+		sprd,control = <0x1>;
+	};
+
+	grp2: rfctl_33 {
+		pins = "SC9860_RFCTL33";
+		function = "func2";
+		sprd,sleep-mode = <AP_SLEEP | PUBCP_SLEEP>;
+		grp2_sleep_mode: rfctl_33_sleep {
+			pins = "SC9860_RFCTL33";
+			sleep-hardware-state;
+			output-low;
+		}
+	};
+
+	grp3: rfctl_misc_20 {
+		pins = "SC9860_RFCTL20_MISC";
+		drive-strength = <10>;
+		bias-pull-up = <4700>;
+		grp3_sleep_mode: rfctl_misc_sleep {
+			pins = "SC9860_RFCTL20_MISC";
+			sleep-hardware-state;
+			bias-pull-up;
+		}
+	};
+};