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Diffstat (limited to 'Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt')
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diff --git a/Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt b/Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt new file mode 100644 index 000000000..b1cea7a3a --- /dev/null +++ b/Documentation/devicetree/bindings/pinctrl/sprd,pinctrl.txt @@ -0,0 +1,83 @@ +* 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. |