CODEWITHSUNDEEP
embedded-linuxdevice-tree
Joe Vince
Joe Vince

Reputation: 355

i2c pin declaration in device tree file?

Any one can help to figure out what the below code mean

especially 0x80000000 important of this value in below device tree node 

i2c-gpio-1 {
        pinctrl_smx6_i2c_gpio_1: i2c-gpio-1grp-smx6 {
            fsl,pins = <
                /* SCL GPIO */
                MX6QDL_PAD_GPIO_6__GPIO1_IO06   0x80000000
                /* SDA GPIO */
                MX6QDL_PAD_KEY_COL2__GPIO4_IO10 0x80000000
            >;
        };
    };

Upvotes: 1

Views: 909

Answers (1)

Longfield
Longfield

Reputation: 1555

This device tree node defines the pinmux configuration for two signals of the imx6q processor on the board to be used as GPIOs (for a bitbanged i2c controller).

The relevant documentation file is: fsl,imx-pinctrl.txt

Especially, this part is relevant here:

Required properties for pin configuration node:

  • fsl,pins: each entry consists of 6 integers and represents the mux and config setting for one pin. The first 5 integers are specified using a PIN_FUNC_ID macro, which can be found in imx*-pinfunc.h under device tree source folder. The last integer CONFIG is the pad setting value like pull-up on this pin. And that's why fsl,pins entry looks like in the example below.

Bits used for CONFIG: NO_PAD_CTL(1 << 31): indicate this pin does not need config.

The two PIN_FUNC_ID macros

MX6QDL_PAD_GPIO_6__GPIO1_IO06, MX6QDL_PAD_KEY_COL2__GPIO4_IO10

are directly taken from this file: imx6q-pinfunc.h

The 0x80000000 value next to these macros is the NO_PAD_CTL(1 << 31) macro from above. This means that that the pins are not configured with the pinmux possibilities detailed there: fsl,imx6q-pinctrl.txt

Upvotes: 3

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