Official sunxi OpenEmbedded layer for Allwinner-based boards.
This layer depends on the additional layers:
Tested with core-image-base.
Maintainers:
- Nicolas Aguirre aguirre.nicolas@gmail.com
- Enrico Butera ebutera@users.sourceforge.net
- Sergey Lapin slapin@ossfans.org
- Marek Belisko marek.belisko@gmail.com
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" KERNEL_DEVICETREE = ""
If you already have built the mainline versions it might be necessary to reset the build directories with:
bitbake -c clean virtual/kernel virtual/bootloader
For mainline kernel we have now support for latest LTS, stable and bleeding edge (latest possible rc).
By default we use latest LTS. If you would like to change version please update PREFERRED_VERSION_linux-mainline in:
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:
Allwinner A20
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 linux-sunxi#25