The hardware controls the multiplexing of General-Purpose Input/Output (GPIO) and alternate functions through the top-level mode multiplexer (TLMM). You can configure the GPIOs during the boot process using the DT properties for TLMM.You can edit the following file paths to update the properties on the Linux host computer:
The default value is GPIO_INPUT. GPIO_INPUT: Allows the state of an input pin to be read. GPIO_OUTPUT: Controls the state of an output pin.
The default value is GPIO_PULL_DOWN. GPIO_PULL_DOWN: Logic 0 connected to Ground. GPIO_PULL_UP: Logic 1 connected to Vdd supply. GPIO_NO_PULL: Floating/High Impedance state. GPIO_KEEPER: Maintains the previous state of the GPIO. When a SoC enters the deepest power-saving mode, this configuration is applied.
The default value is GPIO_OUT_LOW. GPIO_OUT_HIGH: Logic high connected to Vdd.
The default value is GPIO_PRG_NO. GPIO_PRG_YES: Ensures that any unused GPIOs remain in a low-power state after bootup.
For example, (GPIO_INPUT GPIO_PULL_DOWN GPIO_OUT_LOW GPIO_PRG_NO) /* PIN 10 */
ngpios
Number of read only GPIO pins in chipset.
UINT32
–
For example, ngpios = <175>;.
width
Each GPIO pin has its own set of read only control registers. Width indicates pin to pin register offset.
–
–
For example, width = <0x1000>;.
id
Hardware instance of read only GPIO pad ID.
UINT32
–
For example, id = <0x0>;.
version
GPIO read only driver version. Driver 1.0 refers as 0x1.
UINT32
–
For example, version = <0x1>;.
gpio-controller
Identifier to represent the read only connected device as a GPIO device.
String
–
–
phandles for pin configurations
Mux configuration that is used to configure the alternative functionality of GPIOs. For more information, see Pin descriptions.
–
sdc4_data_1: sdc4_data_1 { mux = <13 3>; };
On bootup, the GPIO configures to alternate functionality of GPIO. For example, sdc4_data_1: sdc4_data_1 { mux = <13 3> };. In this example, 13 refers to the GPIO number and 3 indicates the alternate function selection.
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