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>

1 files changed, 83 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt b/Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt
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index 000000000000..b1cea7a3a071
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+* 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.