How to configure SPI2 as a slave?

[ShaneCCC]

You can try use GPIO as CS. Have reference to below relative topic.

TX2 R28.2 SPI CS-GPIO issue

Could you try if remove the cs0 to check if the pin working correct? cs-gpios = <&tegra_main_gpio TEGRA_MAIN_GPIO(X, 6)>, <&tegra_main_gpio TEGRA_MAIN_GPIO(N, 2)>, <&tegra_main_gpio TEGRA_MAIN_GPIO(R, 1)>, <&tegra_main_gpio TEGRA_MAIN_GPIO(T, 3)>, <&tegra_main_gpio TEGRA_MAIN_GPIO(T, 2)>;