ubuntu 18.04 LTS 

查看 swap 分区情况：
$ cat /proc/swaps
飞凌提供的虚拟机默认已经配置好 swap 分区，如果您使用其它虚拟机，可通过创建 swap 文件的
方式来增加 swap 分区大小：
$ sudo fallocate -l 4G /swapfile
$ sudo chmod 600 /swapfile
$ sudo mkswap /swapfile
$ sudo swapon /swapfile
$ sudo vim /etc/fstab
在/etc/fstab 文件最后添加如下内容：/swapfile none swap sw 0 0

预先安装
$ sudo add-apt-repository ppa:openjdk-r/ppa
$ sudo apt-get update
$ sudo apt-get install uuid \
uuid-dev \
zlib1g-dev \
liblz-dev \
liblzo2-2 \
liblzo2-dev \
lzop \
git-core curl \
u-boot-tools \
mtd-utils \
android-tools-fsutils \
openjdk-8-jdk \
device-tree-compiler \
gdisk \
m4 \
libz-dev
$ sudo apt install gcc
$ sudo apt install gcc-multilib
$ sudo apt instal libxml2 libxml2-utils
查看openjdk安装版本：
$ update-java-alternatives -l
修改openjdk版本java-1.8.0-openjdk-amd64 
$ sudo update-alternatives --config java

------------------------------------------------------------------------------------
export LC_ALL=C.UTF-8

FAILED: /bin/bash -c "prebuilts/misc/linux-x86/flex/flex-2.5.39 -oout/host/linux-x86/obj/STATIC_LIBRARIES/libaidl-common_intermediates/aidl_language_l.cpp system/tools/aidl/aidl_language_l.ll"
flex-2.5.39: loadlocale.c:130:_nl_intern_locale_data: ?? 'cnt < (sizeof (_nl_value_type_LC_TIME) / sizeof (_nl_value_type_LC_TIME[0]))' ???
Aborted (core dumped)

-------------------------------------------------------------------------------------
arch/arm64/Makefile:167: recipe for target 'kernel.img' failed
make: *** [kernel.img] Error 127

sudo apt install gcc-multilib

----------------------------------------------------------------------------------------
build/core/ninja.mk:148: recipe for target 'ninja_wrapper' failed
make: *** [ninja_wrapper] Error 1

build-rk3399-all.sh 文件头添加 export LC_ALL=c
sudo apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386
sudo apt-get install m4

------------------------------------------------------------------------------------------
Out of memory error (version 1.2-rc4 'Carnac' (298900 f95d7bdecfceb327f9d201a1348397ed8a843843 by android-jack-team@google.com)).
GC overhead limit exceeded.
Try increasing heap size with java option '-Xmx<size>'.
Warning: This may have produced partial or corrupted output.

1、修改Jack的配置文件prebuilts/sdk/tools/jack-admin

　　这是一个管理Jack的shell脚本，找到start-server函数，直接修改其启动参数，由原来的

JACK_SERVER_COMMAND="java -XX:MaxJavaStackTraceDepth=-1 -Djava.io.tmpdir=$TMPDIR $JACK_SERVER_VM_ARGUMENTS -cp $LAUNCHER_JAR $LAUNCHER_NAME"
更改为

JACK_SERVER_COMMAND="java -XX:MaxJavaStackTraceDepth=-1 -Djava.io.tmpdir=$TMPDIR $JACK_SERVER_VM_ARGUMENTS -Xmx4096m -cp $LAUNCHER_JAR $LAUNCHER_NAME"
　　此时Jack服务器仍然在后台执行，所以我们需要将其停止，然后重启启动(make会自动启动Jack服务器)才能使得修改后的参数生效。

　　我们执行下面的命令此时Jack服务器仍然在后台执行，所以我们需要将其停止，然后重启启动(make会自动启动Jack服务器)才能使得修改后的参数生效。

　　我们执行下面的命令：

#先停止服务
./prebuilts/sdk/tools/jack-admin stop-server

#重新开始服务
./prebuilts/sdk/tools/jack-admin start-server

2. 或者 export JACK_SERVER_VM_ARGUMENTS="-Dfile.encoding=UTF-8 -XX:+TieredCompilation -Xmx4096m"


1920 <- 1280
720


rk3399 kernel通用GPIO驱动控制
内核已经自带了通用GPIO驱动,可以直接在用户空间操作.
路径: /sys/class/gpio
rk3399_mid:/ $ ls /sys/class/gpio                               
export     gpiochip1032 gpiochip1096 unexport 
gpiochip1000 gpiochip1064 gpiochip1128 

操作GPIO0_A6作为高电平输出有效, 操作步骤:
1. 计算对应的gpio number的值
通过/sys/kernel/debug/gpio查询信息:
rk3399_mid:/ $ cat /sys/kernel/debug/gpio                          
GPIOs 1000-1031, platform/pinctrl, gpio0:
gpio-1002 (               |3G_power         ) out lo   
gpio-1004 (               |bt_default_wake_host) in  lo   
gpio-1005 (               |power           ) in  hi   
gpio-1009 (               |bt_default_reset   ) out lo   
gpio-1010 (               |reset           ) out hi   
gpio-1011 (               |pwd_en_3G        ) out hi   

GPIOs 1032-1063, platform/pinctrl, gpio1:
gpio-1033 (               |led_Test         ) in  lo   
gpio-1034 (               |int-n           ) in  hi   
gpio-1035 (               |vbus-5v          ) out hi   
gpio-1045 (               |enable          ) out lo   
gpio-1046 (               |vsel            ) out hi   
gpio-1049 (               |vsel            ) out lo   

GPIOs 1064-1095, platform/pinctrl, gpio2:
gpio-1076 (               |camsys_gpio       ) out lo   
gpio-1083 (               |bt_default_rts     ) in  hi   
gpio-1090 (               |bt_default_wake    ) in  lo   
gpio-1091 (               |camsys_gpio       ) out lo   

可以看到gpio0是以nubmer为1000开始, 那么GPIO0_A6就是 1000+　6 = 1006


2. 设置该gpio为输出
rk3399_mid:/ $ cd /sys/class/gpio/                              
rk3399_mid:/sys/class/gpio $ echo 1006 > export                       
/system/bin/sh: can't create export: Permission denied
1|rk3399_mid:/sys/class/gpio $ su 
rk3399_mid:/sys/class/gpio # echo 1006 > export                       
rk3399_mid:/sys/class/gpio # ls
export  gpiochip1000 gpiochip1064 gpiochip1128 
gpio1006 gpiochip1032 gpiochip1096 unexport    



rk3399_mid:/sys/class/gpio # cd gpio1006/     
rk3399_mid:/sys/class/gpio/gpio1006 # echo out > direction             


3. 设置该gpio输出高电平
rk3399_mid:/sys/class/gpio/gpio1006 # echo 1 > value                   
rk3399_mid:/sys/class/gpio/gpio1006 # cat value                       
1