How can i use gpio bank 3 only for the m4 core

Technical Support
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1

I use the M4 core of imx7 for realtime task. How can I disable the full bank gpio 3 for the A7 core? Do you use any pins of gpio 3 internaly on the imx7 module?

2

Almost all GPIOs on GPIO3 are used by the LCD interface as indicated in the Colibri iMX7 datasheet Table 4.4.1. You can disable the RGB LCD interface in the device tree ( status = "disabled"; ) which will prevent Linux from configuring these pins. Then you can set them up as GPIOs in FreeRTOS on the M4.

More information is available here: FreeRTOS on the Cortex-M4 of a Colibri iMX7

3

Note that you should also disable the GPIO bank on the Linux side by using status = "disabled"; for the gpio3 node.

&gpio3 {
    status = "disabled";
};
4

Also note that using GPIO and using pins are orthogonal issues. E.g. you can use a pin as GPIO on the M4 side, and use other pins as non-GPIO from Linux. Just make sure to not use the same pin on both sides or GPIO’s in the same bank from both sides…