[TDA4VM] Configuring and manipulating GPIO

Hi,

You can identify based on the gpiochip. I agree it is tedious, but there is no other way.

Run following to find out which is the DT node for main_gpio1

root@j7-evm:~# find /proc/device-tree/__symbols__/ | grep gpio
/proc/device-tree/__symbols__/main_gpio_intr
/proc/device-tree/__symbols__/main_gpio7
/proc/device-tree/__symbols__/main_gpio5
/proc/device-tree/__symbols__/wkup_gpio0
/proc/device-tree/__symbols__/main_gpio3
/proc/device-tree/__symbols__/main_gpio1
/proc/device-tree/__symbols__/gpio_keys
/proc/device-tree/__symbols__/wkup_gpio_intr
/proc/device-tree/__symbols__/main_gpio6
/proc/device-tree/__symbols__/wkup_gpio1
/proc/device-tree/__symbols__/main_gpio4
/proc/device-tree/__symbols__/main_gpio2
/proc/device-tree/__symbols__/main_gpio0

Read the content to find the path inside DT

root@j7-evm:~# cat /proc/device-tree/__symbols__/main_gpio1
/interconnect@100000/gpio@601000

root@j7-evm:~#

Now that you know that the gpiochip you are looking for is for the device gpio@601000

You can check which gpiochip is registered with that platform device.

root@j7-evm:~# ls -ls /sys/class/gpio/
total 0
0 --w------- 1 root root 65536 Oct 16 21:30 export
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip0 -> ../../devices/platform/interconnect@100000/interconnect@100000:interconnect@28380000/42110000.gpio/gpio/
gpiochip0
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip212 -> ../../devices/platform/interconnect@100000/601000.gpio/gpio/gpiochip212
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip448 -> ../../devices/platform/interconnect@100000/2010000.i2c/i2c-4/4-0020/gpio/gpiochip448
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip456 -> ../../devices/platform/interconnect@100000/2060000.i2c/i2c-9/9-0020/gpio/gpiochip456
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip464 -> ../../devices/platform/interconnect@100000/2030000.i2c/i2c-6/6-0020/gpio/gpiochip464
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip472 -> ../../devices/platform/interconnect@100000/2000000.i2c/i2c-3/3-0022/gpio/gpiochip472
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip496 -> ../../devices/platform/interconnect@100000/2000000.i2c/i2c-3/3-0020/gpio/gpiochip496
0 lrwxrwxrwx 1 root root 0 Oct 16 21:30 gpiochip84 -> ../../devices/platform/interconnect@100000/600000.gpio/gpio/gpiochip84
0 --w------- 1 root root 65536 Oct 16 21:30 unexport

Once you that the gpiochip212 is representing the main_gpio0, You can simply add 6 in the 212 and the find the pin number.

echo 218 > /sys/class/gpio/export

Above should export the GPIO and you can do read/writes.

However, please make sure that the corresponding pinmux is configured in the DTS.

Use pinmux tool to find out the exact register for programming. Recommendation is to add a devicetree entry for pinmux.

Regards,

Nikhil D

Also, to add more information.

TI EVM has some GPIO expander devices (i2c peripherals), so the entries you see in /sys/class/gpio/ pointing to i2c instance represents those. Ignore them.

By default, only wkup_gpio0, main_gpio0, and main_gpio1 are enabled in Kernel dts. Other gpio banks are disabled.
If the pin you are planning to use falls under disabled gpio banks, you will have to update kernel dts to enable them.

Hi,

You have to add the register offset of the pinmux in the J721E_IOPAD macro.

Check with the marketing contact about enabling you with right pinmux tool.

Following is returned by pinmux tool for GPIO1_6

&main_pmx0 {
mygpio1_pins_default: mygpio1_pins_default {
pinctrl-single,pins = <
J721E_IOPAD(0x21c, PIN_INPUT, 7) /* (W1) I3C0_SDA.GPIO1_6 */
>;
};

};

Regards,

NIkhil D

The bison not found message message is something which is seen if some of the packages are not installed. It may be a proxy setup was wrong and some initial packages did not install.  For a kernel build, you can do a manual setup or you let the installer try and set things up.

You can manually making sure you have bits needed for a kernel build by doing "sudo apt install build-essential libncurses5-dev gcc libssl-dev bc flex bison".  Maybe that helps build the dtbs, but you may have other gaps also.  There are other packages (like u-boot utils) which will be needed for a full kernel build.