Hello,
I've tried to use one pin from the EVM to be used as gpio output from userspace (i.e. sysfs or gpio-hammer). I tried to set the pin as PIN_OUTPUT_PULLUP and GPIO in the 'TI Pinmux Tool'. I got the code for the .dtsi out of the pinmux tool and applied it to the k3-j7*-common-proc*.dts file, following the advice in [e2e.ti.com/.../862697]
I managed to boot and run linux, but I didn't observe what I expect from the userspace gpio tools.
When I write and read-back (either through sysfs or gpio-hammer), I see that the value didn't change.
After playing a bit with the gpiocontroller and going throught the TRM, I understood that the macro J721E_IOPAD does not configure the gpio controller in the appropriate way.
I found out that if bit 18 of the controller is not, I was not able to readback from the gpio.
When he macro is updated as follows:
(k3.h):
-#define PIN_OUTPUT (INPUT_DISABLE | PULL_DISABLE)
-#define PIN_OUTPUT_PULLUP (INPUT_DISABLE | PULL_UP)
-#define PIN_OUTPUT_PULLDOWN (INPUT_DISABLE | PULL_DOWN)
+#define PIN_OUTPUT (INPUT_EN | PULL_DISABLE)
+#define PIN_OUTPUT_PULLUP (INPUT_EN | PULL_UP)
+#define PIN_OUTPUT_PULLDOWN (INPUT_EN | PULL_DOWN)
I'm able to write/readback succesfully. However this does not make much sense from electrical point of view.
Could anyone advise, on what is the correct way to set the GPIOs for the J7-EVM?
