I am struggling to enable the 1.8 V power supply on the camera expansion connector of the TX1 with no camera attached.
In the developer kit carrier board specification the pin is referred to as Pin Nr. 102 with the signal name “DVDD_CAM_IO_1V8” on the camera expansion connector.
The GPIO expander controls this very supply voltage on its pin P11 with the signal name “CAM_VDD_1V8_EN”. A mapping for this pin can be found at /sys/kernel/debug/gpio:
GPIOs 992.1007, i2c/1-0077, tca9539, can sleep: ... gpio-1001 (en-vdd-cam ) out lo ...
Since the pin is already mapped it is blocked by a driver and I am unable to control the GPIO pin by myself. When I try to “echo 1001 > /sys/class/gpio/export” I receive: “write error: Device or resource busy”. Now my idea is to identify the driver which is blocking the GPIO P11 / 1001. Has anybody an idea which driver this might be?
Another approach would be to modify the device tree in order to enable the power supply on boot. The boot log in /var/log/dmesg contains the line “en-vdd-cam: 1800 mV ; Rail OFF”, indicating that the power supply is disabled.
In https://devtalk.nvidia.com/default/topic/975428/jetson-tx1/create-and-include-own-dtsi-files-for-l4t-24-2-fails-at-endpoint-definition/post/5014723/#5014723 the user Atrer posted a code snippet on how to set the power regulators to always on via the dtsi-file. I’m not familiar with the linux device tree and I would like to know where and how I can modify the device tree and add these lines of code to it. Any ideas/references?
Thanks in advance!