Compile NVidia Jetson TX1 kernel on device

There are lots of threads about problems compiling new kernels for their Jetson TX1 boards.  A lot of the issues seem to be related to the cross compilation environment.

The TX1 is pretty beefy, so I figure it can compile its own kernel.  I installed an SSD to give me enough disk space, then copied the source_sync.sh script from the Jetpack installation to the device.  I had it download the 'tegra-l4t-r24.2.1' tag which is currently the latest version.

I copied over the .config file from /usr/src/linux-headers-3.10.96-tegra/ to my kernel/ directory to start with the stock kernel config.  Then I ran make menuconfig to set the additional modules I wanted.

Alas, when I tried to compile with make -j6 zImage, I got errors like this:

  VDSO32C arch/arm64/kernel/vdso32/vgettimeofday.o
/bin/sh: 1: -Wp,-MD,arch/arm64/kernel/vdso32/.vgettimeofday.o.d: not found
/mnt/ocz_ssd/leopard/kernel/arch/arm64/kernel/vdso32/Makefile:40: recipe for target 'arch/arm64/kernel/vdso32/vgettimeofday.o' failed
make[2]: *** [arch/arm64/kernel/vdso32/vgettimeofday.o] Error 127
scripts/Makefile.build:455: recipe for target 'arch/arm64/kernel/vdso32' failed

Apparently it has something to do with backward compatibility to 32-bit ARM, which I don't even care about.   To get around that, I installed the 32-bit toolchain with 'sudo apt-get install gcc-arm-linux-gnueabihf', then export CROSS32CC=arm-linux-gnueabihf-gcc

The next issue was this:

drivers/platform/tegra/tegra21_clocks.c: In function ‘tegra21_cpu_clk_init’:
drivers/platform/tegra/tegra21_clocks.c:1064:31: error: logical not is only applied to the left hand side of comparison [-Werror=logical-not-parentheses]
  c->state = (!is_lp_cluster() == (c->u.cpu.mode == MODE_G)) ? ON : OFF;

That was fixed with an extra set of parentheses:

  c->state = ((!is_lp_cluster()) == (c->u.cpu.mode == MODE_G)) ? ON : OFF;

That seems to do it.  I could then make -j6 zImage as well as Image, modules and (sudo) modules_install, then copy the zImage and Image to /boot.