I have good news. > If you can figure out why the LS-WTGL doesn't work and that can be > fixed (i.e. it turns out to be something other than the size) then I > see no problem with adding support for the LS-WTGL platform.
I finished "git bisect" and good commit is 1553282b11e and bad one is c544d987d9572 (in debian kernel repo). So 3.19.3-1~exp2 is bootable, but 4.0-1~exp1 is non-bootable. I compared the configs, and find former has DEBUG_ICEDCC and latter has DEBUG_LL_UART_NONE. I also find it's not possible to set DEBUG_LL_UART_NONE for 4.0 kernel. After some searches, I tried to set DEBUG_LL_UART_8250 for 4.0 kernel, then the kernel became bootable on my orion5x device! I also find evidences this change is necessary starting for new 4.x kernel: 1. kirkwood changed from 3.16's DEBUG_LL_UART_NONE to 4.x's DEBUG_MVEBU_UART0_ALTERNATE: commit bf56620e4 and 58669ce1 (in debian kernel repo) 2. mainline kernel changed to DEBUG_LL_UART_8250 for orion5x arch: commit 34c64a5d8 (in upstream repo) So I think it's now safe to turn on DEBUG_LL_UART_8250 and merge my patch. Thank you! Cheers, Roger