[FAQ] CCS/TDA4VM: TDA4: How do I determine the GPIO number within linux for a pin within the schematic?

Data Sheet Link: 

www.ti.com/.../tda4vm.pdf

For the sake of demonstration let us take pins: GPMC0_AD10 GPMC0_AD11 GPMC0_AD12  &GPMC0_AD13.

The GPIO numbers in Linux for a pin in schematic can be determined by following the below steps.

1. Get the SoC GPIO Numbers by referring the above TDA4 Data Sheet. Search for GPMC0_AD10 in the data sheet.
   
   
2. Page: 34
   We can observe that GPMC0_AD10 is multiplexed with GPIO0_71. So we have the SoC GPIO Number for GPMC0_AD10.
   
   Similarly we can check:
   

   GPMC0_AD11 It is muxed with GPIO0_72
   GPMC0_AD12 It is muxed with GPIO0_73
   GPMC0_AD13 It is muxed with GPIO0_80
   
   

3. In Linux the GPIO bank numbers are not mapped. The SoC GPIO number is GPIO0_71 i.e 71st GPIO of Main GPIO Bank 0. In the SDK linux directory open the file arch/arm64/boot/dts/ti/k3-j721e-main.dtsi look for main_gpio0.
   The node name for main_gpio0 which is of our interest is gpio@600000. With this we have the MAIN_GPIO0 node string which is used for labeling the
   GPIO Banks while registering in Linux GPIO framework.
   
   
   
4. Boot to Linux prompt & enter the command:
   /sys/class/gpio/gpiochip*/label
   
   Above command will give output like below:
   
   Note: The output may vary based on the GPIO nodes enabled in the device tree but this is to ascertain that we need to figure out which gpiochip corresponds to main_gpio0 with node name gpio@600000 --> 600000.gpio --> gpiochip336.
   
   
   
5. Now we know that 336 maps to 0th GPIO of main_gpio0. 
   So gpio0_71 will map to 336 + 71 = 407 & hence i can form the table: