移植Linux-5.4+内核到4412开发板

原文链接：https://blog.csdn.net/Jason_416/article/details/106772698
作者：Jason416
CSDN博客: Jason416就是我

前言

ITOP-4412开发板被Linux官方支持，所以我们在4412上学习新的内核是非常方便的，本文作者是4412精英群8群一位技术高手，接下来，我们一起来欣赏下他的表演。

环境说明

OS版本

Ubuntu 20 LTS
移植Linux-5.4+内核到4412开发板
交叉编译环境配置

~$ sudo apt install gcc-arm-linux-gnueabihf
~$ sudo apt install flex
~$ sudo apt install bison
~$ sudo apt install u-boot-tools

目标开发板
CPU (Exynos4412，四核Cortex-A9，主频为1.4GHz-1.6GHz)
RAM (1GB 双通道 DDR3)
ROM (8GB EMMC)
其他请见官网链接

开始移植

下载源码

~$ git clone https://github.com/jason416/linux.gi
Note:移植好的源码见博主github仓库的iTop4412分支。

配置内核

2.1 进入内核源码目录

~/linux-5.4$ ls
arch COPYING Documentation include Kbuild lib Makefile README security usr
block CREDITS drivers init Kconfig LICENSES mm samples sound virt
certs crypto fs ipc kernel MAINTAINERS net scripts toolsbr/>jason@jason-vm2:~/arm-develop/linux$
2.2 修改内核配置

说明：
Note: 官方提供了所有三星系列的默认配置，需要先生成一个exynos的配置为基础，再上面再修改成跟板子一致的配置选项即可。
为了避免每次都需要指定ARCH和CROSS_COMPILE变量，可以直接在顶层Makefile直接指定好，如下所示：

选择系统类型
System Type --->
[] Samsung EXYNOS --->
--- Samsung EXYNOS
[] SAMSUNG EXYNOS3
[

] SAMSUNG EXYNOS4
[] SAMSUNG EXYNOS5
EXYNOS SoCs
-- SAMSUNG EXYNOS4210
[
] SAMSUNG EXYNOS4412

配置调试串口 - 设置为UART2
Kernel hacking --->
[] Kernel low-level debugging functions (read help!)
Kernel low-level debugging port (Use Samsung S3C UART 2 for low-level debug) --->
开启串口调试驱动
Device Drivers --->
Character devices --->
Serial drivers --->
<

> Samsung SoC serial support
[] Samsung SoC serial debug
[
] Support for console on Samsung SoC serial port
开启DM96XX网卡驱动
Device Drivers --->
[] Network device support --->
<
> USB Network Adapters --->
<*> Davicom DM96xx based USB 10/100 ethernet devices
设置内核压缩模式为LZMA(非必须，可减小文件大小)
General setup --->
() Build ID Salt
Kernel compression mode (LZMA) --->
编译内核
~/linux-5.4$ make uImage LOADADDR=0x40008000 -j$(nproc)
...
OBJCOPY arch/arm/boot/zImage
Kernel: arch/arm/boot/zImage is ready
UIMAGE arch/arm/boot/uImage
Image Name: Linux-5.4.47
Created: Sun Jun 21 22:41:40 2020
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 5337464 Bytes = 5212.37 KiB = 5.09 MiB
Load Address: 40008000
Entry Point: 40008000
Kernel: arch/arm/boot/uImage is ready
这里需要指定LOADADDR变量，才能生成正确的uImage文件。因为在uboot启动内核时，会先解析uImage中的前64B头信息，定义如下：

修改设备树（以适配开发板）

3.1 说明

在前面的步骤完成后，已经能够编译出可以运行的内核了，但是最后还需要根据板子的差异性，对设备树文件进行调整，以适配目标板。
3.2 修改

屏蔽掉firmware节点(安全相关，不启用，也不知道怎么用…)
修改bus_dmc 节点devfreq-events为devfreq-event
修改regulators 节点参数(参考原理图中的参数)
修改如下：
--- a/arch/arm/boot/dts/exynos4412-itop-scp-core.dtsi
+++ b/arch/arm/boot/dts/exynos4412-itop-scp-core.dtsi
@@ -23,10 +23,12 @@
reg = <0x40000000 0x40000000>;
};

+#if 0
firmware@203f000 {
compatible = "samsung,secure-firmware";
reg = <0x0203F000 0x1000>;
};
+#endif

fixed-rate-clocks {
xxti {
@@ -70,7 +72,7 @@
};

&bus_dmc {

devfreq-events = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>;
devfreq-event = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>;
vdd-supply = <&buck1_reg>;
status = "okay";
};
@@ -167,8 +169,8 @@
regulators {
ldo1_reg: LDO1 {
regulator-name = "VDD_ALIVE";
regulator-min-microvolt = <1100000>;
regulator-max-microvolt = <1100000>;
regulator-min-microvolt = <1000000>;
regulator-max-microvolt = <1000000>;
regulator-always-on;
regulator-boot-on;
op_mode = <1>; / Normal Mode /
@@ -230,8 +232,8 @@

ldo9_reg: LDO9 {
regulator-name = "VDD33_LCD";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-min-microvolt = <3000000>;
regulator-max-microvolt = <3000000>;
op_mode = <1>; / Normal Mode /
};

@@ -252,8 +254,8 @@

   ldo12_reg: LDO12 {
     regulator-name = "VDD33_UOTG";

regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-min-microvolt = <3000000>;
regulator-max-microvolt = <3000000>;
regulator-always-on;
op_mode = <1>; / Normal Mode /
};
@@ -300,8 +302,8 @@
/ Used by HSIC /
ldo18_reg: LDO18 {
regulator-name = "VDDIOPERI_28";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-min-microvolt = <2800000>;
regulator-max-microvolt = <2800000>;
regulator-always-on;
op_mode = <1>; / Normal Mode /
};
@@ -313,15 +315,15 @@

ldo20_reg: LDO20 {
regulator-name = "VDD28_CAM";
regulator-min-microvolt = <1800000>;
regulator-max-microvolt = <2800000>;
regulator-min-microvolt = <3000000>;
regulator-max-microvolt = <3000000>;
op_mode = <1>; / Normal Mode /
};

ldo21_reg: LDO21 {
regulator-name = "VDD28_AF";
regulator-min-microvolt = <1800000>;
regulator-max-microvolt = <2800000>;
regulator-min-microvolt = <3000000>;
regulator-max-microvolt = <3000000>;
op_mode = <1>; / Normal Mode /
};

@@ -341,8 +343,8 @@

   ldo24_reg: LDO24 {
     regulator-name = "VDD33_A31";

regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-min-microvolt = <3000000>;
regulator-max-microvolt = <3000000>;
op_mode = <1>; / Normal Mode /
};

@@ -430,8 +432,8 @@

   buck7_reg: BUCK7 {
     regulator-name = "pvdd_buck7";

regulator-min-microvolt = <750000>;
regulator-max-microvolt = <2000000>;
regulator-min-microvolt = <2050000>;
regulator-max-microvolt = <2050000>;
regulator-boot-on;
regulator-always-on;
op_mode = <1>; / Normal Mode /
3.3 编译dts

~/linux-5.4$ make dtbs