I have not been able to build l4t 28.1 for the TX2 from from source archive provided in the download center.
Multiple files are missing, without any changes I get the following error:
/Linux_for_Tegra/sources/kernel/kernel-4.4/include/linux/platform/tegra/mc.h:28:47: fatal error: linux/platform/tegra/mc-regs-t18x.h: No such file or directory
Adding the missing from a 27.1 branch clears this error but then there are several more files missing as well.
I cannot sync with the Git as the tags are not there for 28.1.
I also cannot use Jetpack 3.1 to download it as I always get an error when running it.