Official sunxi OpenEmbedded layer for Allwinner-based boards.
This layer depends on the additional layer:
Tested with core-image-base.
Kernel / U-Boot Version
Most Allwinner devices and hardware are supported in mainline kernel and U-Boot, so this layer builds mainline by default. There is a custom U-Boot and Kernel version for sunxi devices which includes some special drivers not mainlined. These versions are rather old (3.4 for kernel and 2014.04 for U-Boot), but may support more functions and devices than current mainline
If you want to switch back to sunxi versions for some reasons (no device tree available, unsupported hardware), either:
- change the file conf/machine/include/sunxi.inc to include the following block
edit your conf/local.conf to add the following block
PREFERRED_PROVIDER_u-boot="u-boot-sunxi" PREFERRED_PROVIDER_virtual/bootloader="u-boot-sunxi" PREFERRED_PROVIDER_virtual/kernel="linux-sunxi"
If you already have built the mainline versions it might be necessary to reset the build directories with:
bitbake -c clean linux bitbake -c clean u-boot
Also, older kernel versions such as this don't build successfully with any gcc version 5.0 or newer. Since gcc-5.2 is the current default compiler on master, if you wish to build this kernel with master you'll need to add the following to your conf/local.conf:
GCCVERSION = "4.9%"
The default machine settings are meant to be the lowest common denominator, maximizing generality. Significantly better performance (2x-3x) can be achieved with the following settings:
For Allwinner A20 (Cubieboard2/CubieTruck), the following tuning options are recommended:
Enable hardfloat, thumb2 and neon capabilities
DEFAULTTUNE = "cortexa7hf-neon-vfpv4"
This tuning profile takes advantage of the Allwinner A20 hardfloat, neon and vfpv4 capabilities.
Change CPU governor to ondemand, and tune settings
echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor echo 336000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq echo 912000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq #More aggressive #echo 1008000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq echo 40 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold echo 200000 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate
This code changes the default CPU governor from fantasy to ondemand, and tunes its settings, as recommended at http://linux-sunxi.org/Cpufreq
For additional discussion, see https://github.com/linux-sunxi/meta-sunxi/issues/25