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(These are notes about the WM8505 kernel port, please see README.linux for the original Linux kernel README.) * This is based on kernel 2.6.29 sources released by VIA (http://lists.gpl-violations.org/pipermail/legal/2010-July/002204.html). * You may also want to see http://gitorious.org/linux-on-via-vt8500 which is a clean kernel implementation for VT8500/WM8505, written largely from scratch. However, at time of writing the clean kernel supports less WM8505 hardware than this kernel does. * These sources currently come with one sourceless binary object file (for SD card support.) * This kernel will not work on VT8500-based machines. WM8505 only. ******** PREREQUISITES ******** - A host running Linux to build from. You may be able to build from BSD/OSX as well, I don't know. - An appropriate ARM cross-compiler toolchain. Make sure it has EABI support. Recommended/tested choices are Emdebian for Debian/Ubuntu hosts, or the Android NDK toolchain for other hosts (see below.) Problems have been reported using CodeSourcery. - The mkimage tool installed on your host. On Debian/Ubuntu, the package to install is 'uboot-mkimage' ******** INSTALLING A TOOLCHAIN ******** **** Emdebian Option To install Emdebian on an Debian or Ubuntu host, follow the steps under "Get the Binaries" on emdebian wiki: http://wiki.debian.org/EmdebianToolchain#Getthebinaries (you don't need all those packages listed there to just compile a kernel, but they don't hurt.) Before building, you will need to set an environment variable for your cross-compiler: export CROSS_COMPILE=arm-linux-gnueabi- (you can alternately supply this on the command-line to make, if you desire.) **** Android NDK Option To install the Android NDK, first download from http://developer.android.com/sdk/ndk/index.html Then untar it to your chosen install point and add the prebuilt binary toolchain to your path. The steps will be something like: cd /usr/local sudo tar jxvf ~/Downloads/android-ndk-r5b-linux-x86.tar.bz2 sudo chmod -R +rX android-ndk-r5b/ export PATH="$PATH:`pwd`/android-ndk-r5b/toolchains/arm-eabi-4.4.0/prebuilt/linux-x86/bin" You will probably want to add the last line above to your .bashrc or similar, so the toolchain is always in your PATH You will also need to set the cross-compiler environment variable: export CROSS_COMPILE=arm-eabi- (you can alternately supply this on the command-line to make, if you desire.) ******** CONFIGURE YOUR FIRST KERNEL ******** After you have a toolchain, you can configure a WM8505 kernel with a default config (defconfig) as follows: For Eken M001 kernel suitable for Android: make eken_m001_android_defconfig ARCH=arm For Eken M001 kernel more suitable for Debian: make eken_m001_debian_defconfig ARCH=arm (Other WM8505 tablets/netbooks can probably use the M001 config as well.) ******** BUILD YOUR FIRST KERNEL ******** After you have a config, you can build a kernel: make via_obj uImage modules ARCH=arm If compilation succeeds, the kernel image will be at arch/arm/uImage (this file is equivalent to the uzImage.bin file used in common WM8505 boot environments, you can copy it over the top to change the kernel which is installed/booted from SD.) To install the built kernel modules somewhere, run: make modules_install ARCH=arm INSTALL_MOD_PATH=/some/staging/path ******** FURTHER CONFIGURATION ********** You can edit the current config with make menuconfig ARCH=arm As well as the two recommended defconfigs, there are some older configurations available under arch/arm/configs. These are not known to work, and are mostly for comparison/information purposes only: * arch/arm/configs/android_wm8505_config * arch/arm/configs/wmt_defconfig These two came as-is with the source tarball. * arch/arm/configs/wm8505_initial_config This file was the .config that came as-is the source tarball (different to the above two configs.) * arch/arm/configs/eken_m001_factory_configuration This is a dump of /proc/config.gz on a factory Eken M001 kernel (different again.) ******** OTHER BUILDING NOTES ******** * The via_obj target is a custom VIA target to copy the mmc_atsmb.o file into the source tree before building. VIA/Wondermedia have not released this one source file. * If you are building for Android, and you want to use some of the binary-only kernel modules that came with WM8505 Android by default (or vice-versa if you want to use a new module with an old kernel), then you need to force the kernel revision so they will load. This is a horrible hack, but even WM seem to do it in their Android releases. Do this by overriding the KERNELRELEASE make variable on the command line as KERNELRELEASE=2.6.29-00236-g4f8dbbb-dirty - ie: make uImage modules ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- KERNELRELEASE=2.6.29-00236-g4f8dbbb-dirty **** u-boot scripts U-boot boot scripts for SD card booting/installing are saved at the path 'script/scriptcmd' on SD card. To read a scriptcmd: tail -c +72 scriptcmd To write a scriptcmd: mkimage -A arm -O linux -T script -C none -a 1 -e 0 -n "script image" -d cmd scriptcmd (Where 'cmd' is your source scriptcmd script.) ******* kernel arguments ****** Scriptcmd has a line for kernel args: setenv bootargs mem=112M root=/dev/mmcblk0p2 lcdid=1 console=ttyS0,115200n Relevant args: * mem=112M is also mem=109M on non-Android boots. Suspect extra 3M is video memory?!? * console=ttyS0,115200n gives you kernel console on serial. If you're building for Debian or any other non-Android userland then you may want to remove this, and enable framebuffer console in configuration (this is enabled already in Debian defconfig.) * lcdid=1 enables VOUT to LCD on tablets. Some other machines (netbooks?) use VT1632 which is the default if lcdid is not set (in this case, you won't see any video on a tablet.) ****** WiFi Driver ****** This tree contains the rt2870sta kernel module, backported from kernel 2.6.35. I have had mixed success with this driver, you may also want to try Ralink's OEM source release driver (especially on Android.) The WiFi driver that ships with WM8505 Android is a custom one with vendor-specific patches to enable the GPIO and load the firmware. If you go with a standard driver, you will need to perform these functions yourself: - Run these commands to turn on the Signal GPIO that powers the USB stick inside the Eken. We'll probably come up with something better eventually, but for now: echo out > /sys/class/gpio/gpio2/direction echo 1 > /sys/class/gpio/gpio2/value modprobe rt2870sta - Install a firmware file. To get a firmware file in debian, you can install firmware-ralink from non-free. Alternatively, download the USB firmwares from http://www.ralink.com.tw/support.php?s=2 The rt2870.bin firmware will do as long as it's recent. You can choose to load the firmware at runtime, or to compile it directly into the kernel. Choosing to compile it in is currently the path of least resistance for most userlands (look in menuconfig under (under Device Drivers -> Generic Driver Options -> Include in-kernel firmware blobs...)