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ff04b40152
Remove the list of possible pin configurations from the documentation file and create header files containing those definitions. This eliminates the need for error-prone manual lookup of those values in the documentation and guarantees consistency between the human readable representation of the pad function in the .dts file and the actual binary value used in DT. Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
128 lines
5.0 KiB
Plaintext
128 lines
5.0 KiB
Plaintext
* Freescale MXS Pin Controller
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The pins controlled by mxs pin controller are organized in banks, each bank
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has 32 pins. Each pin has 4 multiplexing functions, and generally, the 4th
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function is GPIO. The configuration on the pins includes drive strength,
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voltage and pull-up.
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Required properties:
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- compatible: "fsl,imx23-pinctrl" or "fsl,imx28-pinctrl"
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- reg: Should contain the register physical address and length for the
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pin controller.
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Please refer to pinctrl-bindings.txt in this directory for details of the
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common pinctrl bindings used by client devices.
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The node of mxs pin controller acts as a container for an arbitrary number of
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subnodes. Each of these subnodes represents some desired configuration for
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a group of pins, and only affects those parameters that are explicitly listed.
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In other words, a subnode that describes a drive strength parameter implies no
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information about pull-up. For this reason, even seemingly boolean values are
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actually tristates in this binding: unspecified, off, or on. Unspecified is
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represented as an absent property, and off/on are represented as integer
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values 0 and 1.
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Those subnodes under mxs pin controller node will fall into two categories.
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One is to set up a group of pins for a function, both mux selection and pin
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configurations, and it's called group node in the binding document. The other
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one is to adjust the pin configuration for some particular pins that need a
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different configuration than what is defined in group node. The binding
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document calls this type of node config node.
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On mxs, there is no hardware pin group. The pin group in this binding only
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means a group of pins put together for particular peripheral to work in
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particular function, like SSP0 functioning as mmc0-8bit. That said, the
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group node should include all the pins needed for one function rather than
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having these pins defined in several group nodes. It also means each of
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"pinctrl-*" phandle in client device node should only have one group node
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pointed in there, while the phandle can have multiple config node referenced
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there to adjust configurations for some pins in the group.
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Required subnode-properties:
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- fsl,pinmux-ids: An integer array. Each integer in the array specify a pin
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with given mux function, with bank, pin and mux packed as below.
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[15..12] : bank number
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[11..4] : pin number
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[3..0] : mux selection
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This integer with mux selection packed is used as an entity by both group
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and config nodes to identify a pin. The mux selection in the integer takes
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effects only on group node, and will get ignored by driver with config node,
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since config node is only meant to set up pin configurations.
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Valid values for these integers are listed below.
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- reg: Should be the index of the group nodes for same function. This property
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is required only for group nodes, and should not be present in any config
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nodes.
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Optional subnode-properties:
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- fsl,drive-strength: Integer.
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0: MXS_DRIVE_4mA
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1: MXS_DRIVE_8mA
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2: MXS_DRIVE_12mA
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3: MXS_DRIVE_16mA
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- fsl,voltage: Integer.
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0: MXS_VOLTAGE_LOW - 1.8 V
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1: MXS_VOLTAGE_HIGH - 3.3 V
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- fsl,pull-up: Integer.
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0: MXS_PULL_DISABLE - Disable the internal pull-up
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1: MXS_PULL_ENABLE - Enable the internal pull-up
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Note that when enabling the pull-up, the internal pad keeper gets disabled.
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Also, some pins doesn't have a pull up, in that case, setting the fsl,pull-up
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will only disable the internal pad keeper.
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Examples:
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pinctrl@80018000 {
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#address-cells = <1>;
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#size-cells = <0>;
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compatible = "fsl,imx28-pinctrl";
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reg = <0x80018000 2000>;
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mmc0_8bit_pins_a: mmc0-8bit@0 {
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reg = <0>;
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fsl,pinmux-ids = <
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MX28_PAD_SSP0_DATA0__SSP0_D0
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MX28_PAD_SSP0_DATA1__SSP0_D1
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MX28_PAD_SSP0_DATA2__SSP0_D2
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MX28_PAD_SSP0_DATA3__SSP0_D3
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MX28_PAD_SSP0_DATA4__SSP0_D4
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MX28_PAD_SSP0_DATA5__SSP0_D5
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MX28_PAD_SSP0_DATA6__SSP0_D6
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MX28_PAD_SSP0_DATA7__SSP0_D7
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MX28_PAD_SSP0_CMD__SSP0_CMD
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MX28_PAD_SSP0_DETECT__SSP0_CARD_DETECT
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MX28_PAD_SSP0_SCK__SSP0_SCK
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>;
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fsl,drive-strength = <MXS_DRIVE_4mA>;
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fsl,voltage = <MXS_VOLTAGE_HIGH>;
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fsl,pull-up = <MXS_PULL_ENABLE>;
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};
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mmc_cd_cfg: mmc-cd-cfg {
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fsl,pinmux-ids = <MX28_PAD_SSP0_DETECT__SSP0_CARD_DETECT>;
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fsl,pull-up = <MXS_PULL_DISABLE>;
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};
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mmc_sck_cfg: mmc-sck-cfg {
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fsl,pinmux-ids = <MX28_PAD_SSP0_SCK__SSP0_SCK>;
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fsl,drive-strength = <MXS_DRIVE_12mA>;
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fsl,pull-up = <MXS_PULL_DISABLE>;
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};
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};
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In this example, group node mmc0-8bit defines a group of pins for mxs SSP0
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to function as a 8-bit mmc device, with 8mA, 3.3V and pull-up configurations
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applied on all these pins. And config nodes mmc-cd-cfg and mmc-sck-cfg are
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adjusting the configuration for pins card-detection and clock from what group
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node mmc0-8bit defines. Only the configuration properties to be adjusted need
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to be listed in the config nodes.
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Valid values for i.MX28/i.MX23 pinmux-id are defined in
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arch/arm/boot/dts/imx28-pinfunc.h and arch/arm/boot/dts/imx23-pinfunc.h.
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The definitions for the padconfig properties can be found in
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arch/arm/boot/dts/mxs-pinfunc.h.
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