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