We are trying to use this GPIO to enable an output buffer.
I’ve removed the camera from the DTB, so it shows up unused
in /sys/kernel/debug/gpio. If my math is correct, the GPIO
number is 456.
The problem is that immediately on applying power, we get a roughly
1.3 mhz signal out of the pin which doesn’t seem to stop, ever.
This makes it impossible to control the output buffer.
Any idea why this pin would act this way? This happens within a
fraction of a second after power-up, so it’s not like the kernel
or any drivers are doing this.
The Tegra X2 IC ball name is QSPI_SCK. The frequency of 1.3 MHz is right in line with what frequency some QSPI chips might communicate at. My guess is that that the Tegra X2 Boot ROM, or other early MB code, is doing a QSPI read/check operation and the pin has not been configured properly. Are you sure you have a properly programmed BCT on your device to put G8/PR.00 in GPIO mode configuration with a GPIO output setting?
If you do have it configured properly, then it might be something out of your control. Someone else should be able to check their board and see the same thing you are if it is completely out of your control and the Boot ROM is doing it before it has ever configured the pinmuxing.
This could have been it. We just used a different GPIO for now as a work around, and now it
works properly. Clocking data in using the files in /sys/class/gpio is kind of slow though.