1.插入環境變數：

cd  /etc

vim  profile

在末尾加入：export  PATH=<sdk path>/linux-devkit/sysroots/x86_64-arago-linux/usr/bin:$PATH

Rebuild source  using the top-level makefile in the SDK rootdirectory.

·        make allrebuilds all components in the SDK

·        makelinux configures and builds the kernel

·        makeu-boot-spl builds u-boot and u-boot-spl

2.清除Kernel原始碼

make ARCH=armCROSS_COMPILE=arm-linux-gnueabihf- distclean

3.配置核心

在編譯核心之前，需要配置哪些元件成核心映象，哪些模組作為動態模組，

3.1預設配置

                    make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- defconfig

After the configuration step has run the full configuration file is saved to the root of the kernel tree as .config. 

e.g:  make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-am335x_evm_defconfig

3.2定製化配置

                    make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- menuconfig 

3.3編譯核心

                    make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- zImage

This will result in a kernel image filebeing created in the arch/arm/boot/directory called zImage.

3.4編譯裝置樹

在arch/arm/boot/dts/目錄下：

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- am335x-evmsk .dtb

3.5編譯核心模組

   很多驅動沒有整合到zImage裡面，而是在動態模組中。

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- modules

這會生成kernel object（.ko）檔案。

4.安裝kernel

 4.1 將zImage 、 dtb 拷貝在資料夾（從這裡開始讀）Installing the Kernel Image and Device TreeBinaries。

cd <kernelsources dir>
sudo cparch/arm/boot/zImage <rootfs path>/boot
sudo cparch/arm/boot/dts/<dt file>.dtb <rootfs path>/boot

例如：if you wanted to copy the kernel image and BeagleBone Black devicetree file to the rootfs partition of a SD card you would enter the below commands

cd <kernelsources dir>
sudo cparch/arm/boot/zImage arch/arm/boot/dts/am335x-boneblack.dtb /media/rootfs/boot

4.2安裝模組

sudomake ARCH=arm  INSTALL_MOD_PATH=<pathto root of file system> modules_install

For example if you are installing the moduleson the rootfs partition of the SD card you would do:

sudo make ARCH=arm INSTALL_MOD_PATH=/media/rootfsmodules_install

5.GPIO

http://processors.wiki.ti.com/index.php?title=Linux_PSP_GPIO_Driver_Guide&keyMatch=gpio&tisearch=Search-EN

http://processors.wiki.ti.com/index.php/Processor_SDK_Linux_GPIO_Driver_Overview

IRQ handling:

irq_num = gpio_to_irq(30)

• Request IRQ, make sure that irq_num should be non-error value

request_irq(irq_num, handler, 0,"gpio_test", NULL);

• Set IRQ type Raising/Falling/Level triggered

set_irq_type(irq_num, IRQ_TYPE_EDGE_RISING);

• During the clean-up path free the IRQ and gpio

free_irq(irq_num, NULL);

gpio_free(30);

Kernel Level

err = gpio_request(30,"sample_name");

gpio_direction_input(30);

Make pin 30 as output and set the value ashigh.

gpio_direction_output(30, 1);

Exporting that particular pin (30) to sysfsentry then use this API

gpio_export(30, true);

gpio_get_value(30);

User Space - Sysfs control

Enable GPIO sysfs support in kernelconfiguration and build the kernel

Device Drivers  ---> GPIOSupport  ---> /sys/class/gpio/...(sysfs interface)

Sysfs entries

Export the particular GPIO pin for usercontrol. GPIO30 is taken as example.

$ echo 30 >/sys/class/gpio/export

Change the GPIO pin direction to in/out

$ echo "out"> /sys/class/gpio/gpio30/direction

or

$ echo "in"> /sys/class/gpio/gpio30/direction

Change the value

$ echo 1 >/sys/class/gpio/gpio30/value

or

$ echo 0 >/sys/class/gpio/gpio30/value

Unexport the GPIO pin

$ echo 30 >/sys/class/gpio/unexport

檢視GPIO被請求的情況

Run these commands for knowing what are theGPIO's already requested in the drivers.

$ mount -t debugfs debugfs /sys/kernel/debug

$ cat /sys/kernel/debug/gpio

檢視裝置號

$ cat /proc/devices

$ mknod /dev/裝置名  c 主裝置號 0

6. 核心原始碼分析網址

http://www.cnblogs.com/zengjfgit/p/4788923.html