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How can I configure GPIOs on the TDA4 EVM using the following methods:
-1-
Using sysfs: (https://www.kernel.org/doc/Documentation/gpio/sysfs.txt)
Steps:
Let us assume we want to toggle GPIO0_127
Step1
Run the following:
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_gpio0 /interconnect@100000/gpio@600000
Now that you know that the gpiochip you are looking for is for the device gpio@600000
You can check which gpiochip is registered with that platform device.
root@j7-evm:~# ls -la /sys/class/gpio/ drwxr-xr-x 2 root root 0 Feb 17 08:38 . drwxr-xr-x 60 root root 0 Feb 17 08:38 .. --w------- 1 root root 65536 Feb 17 08:38 export lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip0 -> ../../devices/platform/interconnect@100000/interconnect@100000:interconnect@28380000/42110000.gpio/gpio/gpiochip0 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip212 -> ../../devices/platform/interconnect@100000/601000.gpio/gpio/gpiochip212 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip448 -> ../../devices/platform/interconnect@100000/2010000.i2c/i2c-4/4-0020/gpio/gpiochip448 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip456 -> ../../devices/platform/interconnect@100000/2060000.i2c/i2c-9/9-0020/gpio/gpiochip456 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip464 -> ../../devices/platform/interconnect@100000/2030000.i2c/i2c-6/6-0020/gpio/gpiochip464 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip472 -> ../../devices/platform/interconnect@100000/2000000.i2c/i2c-3/3-0022/gpio/gpiochip472 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip496 -> ../../devices/platform/interconnect@100000/2000000.i2c/i2c-3/3-0020/gpio/gpiochip496 lrwxrwxrwx 1 root root 0 Feb 17 08:38 gpiochip84 -> ../../devices/platform/interconnect@100000/600000.gpio/gpio/gpiochip84 --w------- 1 root root 65536 Feb 17 08:38 unexport
Now you know that gpiochip84 represents main_gpio0 or GPIO0
Step2 and Step3
Add 127 to this, i.e. 84 + 127 = 211
root@j7-evm:~# cd /sys/class/gpio/ root@j7-evm:/sys/class/gpio# echo 211 > export root@j7-evm:/sys/class/gpio# cd gpio211 root@j7-evm:/sys/class/gpio/gpio211# echo out > direction root@j7-evm:/sys/class/gpio/gpio100# echo 1 > value
Above should export the GPIO and you can do read/writes.
NOTE:
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.
-2-
Using Device tree
Let us assume we want to toggle GPIO0_127
Step1: In the board specific DTS - k3-j721e-common-proc-board.dts add the following
&main_pmx0 {
+
+ mygpio1_pins_default: mygpio1_pins_default {
+ pinctrl-single,pins = <
+ J721E_IOPAD(0x200, PIN_INPUT, 7) /* (AC4) UART1_CTSn.GPIO0_127 */
+ >;
+ };
}
Step2: In the same board specific DTS, hog the GPIO (https://www.kernel.org/doc/Documentation/devicetree/bindings/gpio/gpio.txt)
+&m_can2 {
+ status = "okay";
+ pinctrl-names = "default";
+ pinctrl-0 = <&mcan2_gpio_pins_default &mygpio1_pins_default>; /* mygpio1_pins_default for PINMUXing the GPIO0_127 */
+ can-transceiver {
+ max-bitrate = <5000000>;
+ };
+};
+ mygpio1_pins_default: mygpio1_pins_default {
+ pinctrl-single,pins = <
+ J721E_IOPAD(0x200, PIN_INPUT, 7) /* (AC4) UART1_CTSn.GPIO0_127 */
+ >;
+ };
The above will do a one time configuration of the GPIO from the kernel. Note that GPIOs already being used can not be exported using the sysfs. So in case you do the above, you will not be able to export this GPIO (as mentioned in 1) and change it back again.
The sysfs interface can be used for quick testing and then the changes can be made to the device tree. Please also note that any of the changes will take in effect only when you have the correct Pinmux.
Regards,
Karan
Along with SoC GPIOs we can also configure GPIOs coming from I2C expanders.
One way to do that is to hog the GPIO (https://www.kernel.org/doc/Documentation/devicetree/bindings/gpio/gpio.txt) in the same way as we did before. There are examples existing in the k3-j721e-common-proc-board.dts
The other way is to do I2C transactions from the user-space to do some tests before actually moving that code to the Device Tree.
We can use i2c-get and i2c-set commands.
For that we need to do the following steps:
Example:
Let us take an example where we want to set i2c0 chip 0x22.
k3-j721e-main.dtsi:
1413 main_i2c0: i2c@2000000 {
1414 compatible = "ti,j721e-i2c", "ti,omap4-i2c";
1415 reg = <0x0 0x2000000 0x0 0x100>;
1416 interrupts = <GIC_SPI 200 IRQ_TYPE_LEVEL_HIGH>;
1417 #address-cells = <1>;
1418 #size-cells = <0>;
1419 clock-names = "fck";
1420 clocks = <&k3_clks 187 0>;
1421 power-domains = <&k3_pds 187 TI_SCI_PD_SHARED>;
1422 };
from the user-space run the following:
root@j7-evm:~# dmesg | grep i2c [ 0.685447] i2c /dev entries driver [ 0.823948] omap_i2c 40b00000.i2c: bus 0 rev0.12 at 100 kHz [ 0.829869] omap_i2c 40b10000.i2c: bus 1 rev0.12 at 100 kHz [ 0.835846] omap_i2c 42120000.i2c: bus 2 rev0.12 at 100 kHz [ 0.928222] omap_i2c 2000000.i2c: bus 3 rev0.12 at 400 kHz [ 0.934237] omap_i2c 2010000.i2c: bus 4 rev0.12 at 400 kHz [ 0.940117] omap_i2c 2020000.i2c: bus 5 rev0.12 at 100 kHz [ 0.986345] omap_i2c 2030000.i2c: bus 6 rev0.12 at 400 kHz [ 0.992200] omap_i2c 2040000.i2c: bus 7 rev0.12 at 100 kHz [ 0.998053] omap_i2c 2050000.i2c: bus 8 rev0.12 at 100 kHz [ 1.040217] omap_i2c 2060000.i2c: bus 9 rev0.12 at 400 kHz
We see i2c@2000000 -> main_i2c0 -> i2c bus 3 here.
So in the i2c-set command we need to use this number "3" to access the chip connected at 0x22 to main_i2c0.
Regards,
Karan