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Compile custom chromeos kernel to get cuda working again

June 01, 2015

Custom chromeos kernel steps

Latest (20 May 2015) update of chromeos for Acer Chromebook 13 changed the nvidia built in driver and cuda is no longer supported. This post will show how to compile a working kernel from chrubuntu

Steps

  1. Download couple of packages:

     sudo apt-get install u-boot-tools device-tree-compiler vboot-kernel-utils

  2. From chrubuntu clone git repo for kernel. This version looks like it's working ok: release-R41-6680.B-chromeos-3.10 [3]

     git clone https://chromium.googlesource.com/chromiumos/third_party/kernel -b release-R41-6680.B-chromeos-3.10

  3. Get firmware package for xhci

     wget http://commondatastorage.googleapis.com/chromeos-localmirror/distfiles/xhci-firmware-2014.11.06.00.00.tbz2
 tar xf xhci-firmware-2014.11.06.00.00.tbz2
 cd kernel
 cp -r ../lib/firmware .

  4. Set build environment. We are using chrubuntu directly, hence there is no need for cross compilation, but good instructions are in [1] and [2]

     export WIFIVERSION="-3.8"
 export ARCH=arm

  5. Set up initial config

     ./chromeos/scripts/prepareconfig chromeos-tegra

  6. Run menuconfig to set firmware location Device Driver / General Options / External firmware location: nvidia/tegra124/xusb.bin

     make menuconfig

  7. Finaly compile the kernel and modules. Get a cup of coffee or a tea

     make -j 4 zImage modules
 make tegra124-nyan-big.dtb

  8. Build kernel image

     wget https://raw.githubusercontent.com/lgeek/gnu-linux-on-acer-chromebook-13/master/nyan-big-fit.cfg
 mkimage -f nyan-big-fit.cfg nyan-big-kernel
 echo "noinitrd console=tty1 debug verbose root=/dev/mmcblk1p7 rootwait rw lsm.module_locking=0 net.ifnames=0 rootfstype=ext4" > ./cmdline
 vbutil_kernel --arch arm --pack kernel.bin --keyblock /usr/share/vboot/devkeys/kernel.keyblock --signprivate /usr/share/vboot/devkeys/kernel_data_key.vbprivk --version 1 --config cmdline --vmlinuz nyan-big-kernel

  9. Install modules and kernel. In my case boot partition is mmcblk1p6:

     sudo WIFIVERSION=-3.8 ARCH=arm make modules_install
 dd if=./kernel.bin of=/dev/mmcblk1p6
 sudo dd if=./kernel.bin of=/dev/mmcblk1p6
 sudo reboot

  10. Enjoy your cup of coffe (or tea) while running cuda computations.

[1] https://github.com/lgeek/gnu-linux-on-acer-chromebook-13
[2] http://www.vctlabs.com/posts/2015/Jan/22/tegra_chromebook_hack/
[3] https://groups.google.com/a/chromium.org/forum/#!topic/chromium-os-dev/u9DmbSYWduo)

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