maybe you can refer to the link as below, get the repo from tsinghua
"https://mirrors.tuna.tsinghua.edu.cn/help/git-rep"
I suggest that you can update to the latest version, some packages in the git.freescale.com are removed, if you build the 3.14.28, maybe you will get the connection error even if you can repo sync successfully, I have built 4.14.52 successfully before, but I don't know if you can get 3.14.28 source package or not