嵌入式学习笔记201-Linux kernel动起来

1. 在前篇博文《嵌入式学习笔记200-Linux kernel初体验》在已经确保环境编译是ok的，接下来让kernel能够最基本的动起来，起码可以看到基本的启动打印！
2. 修改外部输入时钟频率， 修改 linux-2.6.30.4\arch\arm\mach-s3c2440\mach-smdk2440.c 在大概163行将16934400改成12000000。

static void __init smdk2440_map_io(void)
{
    s3c24xx_init_io(smdk2440_iodesc, ARRAY_SIZE(smdk2440_iodesc));
    s3c24xx_init_clocks(16934400);
    s3c24xx_init_uarts(smdk2440_uartcfgs, ARRAY_SIZE(smdk2440_uartcfgs));
}

3.修改menuconfig配置，由于我的交叉编译是4.3.3version的，需要选择如下红色两行，如果是3.4.5的就不用，其他version的就不清楚了。

4.修改机器码，由于之前我们在设置uboot时，u-boot-1.1.6\board\tq2440\tq2440.c –> board_init –>gd->bd->bi_arch_number = MACH_TYPE_TQ2440; , 其中MACH_TYPE_TQ2440在include\asm-arm\mach-types.h 下#define MACH_TYPE_TQ2440 1003， 所以在linux-2.6.30.4\arch\arm\tools\mach-types 的379行改成s3c2440 ARCH_S3C2440 S3C2440 1003即可，至于是什么魔数不重要 ，只要跟uboot的一致即可，当然不能跟原有的冲突。

1. 接着执行 make，会在 arch/arm/boot下生成 zImage，此时的镜像文件还不能给uboot识别，因为前篇博文提到uboot在调用boot_linux时会解析linux，所以要加个头部信息，在zImage目录下执行： mkimage -n ‘linux-2.6.30.4’ -A arm -O linux -T kernel -C none -a 0x30008000 -e 0x30008000 -d zImage zImage.bin，会有如下打印：
   Image Name: linux-2.6.30.4
   Created: Sat May 23 16:43:06 2015
   Image Type: ARM Linux Kernel Image (uncompressed)
   Data Size: 1904596 Bytes = 1859.96 kB = 1.82 MB
   Load Address: 0x30008000
   Entry Point: 0x30008000
   各项意思是：
   -A ==> set architecture to ‘arch’
   -O ==> set operating system to ‘os’
   -T ==> set image type to ‘type’
   -C ==> set compression type ‘comp’
   -a ==> set load address to ‘addr’ (hex)
   -e ==> set entry point to ‘ep’ (hex)
   -n ==> set image name to ‘name’
   -d ==> use image data from ‘datafile’
   -x ==> set XIP (execute in place)
   我们的镜像是非加密的所以-C none，至于运行地址0x30008000 随便 只是推荐这个地方而已由于入口函数在kernel的最前面，而最前面在0x30008000 ，所以入口地址也就在0x30008000

6.烧入到nand flash，可以借助烧录器烧入或者uboot的ftp功能，这里我借助天嵌具有烧入功能的bootloader，它已经烧入在nor flash，只要将拨码开关拨到nor选项启动即可，通过选择3即可烧 zImage.bin：

首先bootloader会将code download SDRAM内存再调用nand接口写入，不过写入的地址kernel是在0x200000 size=0x300000是固定的（天嵌的bootloader code写固定的），所以到时在修改kernelnand分区时要注意到这点，如果你是用烧录器的话那地址你可以自己定。最后将拨码卡开关拨到nand flash启动即可，当然前提是你有烧入好uboot并且支持启动linux。
前面的博文都是借由这一方式的，相信读者并不陌生。
如果事先有uboot的会有如下打印：

U-Boot 1.1.6 (May 23 2015 - 16:37:20)

DRAM:  64 MB
Flash:  2 MB
NAND:  256 MiB
*** Warning - bad CRC or NAND, using default environment

In:    serial
Out:   serial
Err:   serial
Hit any key to stop autoboot:  0 

NAND read: device 0 offset 0x200000, size 0x300000
 3145728 bytes read: OK
## Booting image at 32000000 ...
   Image Name:   linux-2.6.30.4
   Created:      2015-05-23   8:43:06 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1904596 Bytes =  1.8 MB
   Load Address: 30008000
   Entry Point:  30008000
   Verifying Checksum ... OK
OK

Starting kernel ...

Uncompressing Linux........................................................................................................................ done, booting the kernel.
Linux version 2.6.30.4 (vedic@vedic-VirtualBox) (gcc version 4.3.3 (Sourcery G++ Lite 2009q1-176) ) #1 Sat May 23 16:09:48 HKT 2015
CPU: ARM920T [41129200] revision 0 (ARMv4T), cr=c0007177
CPU: VIVT data cache, VIVT instruction cache
Machine: SMDK2440
Memory policy: ECC disabled, Data cache writeback
CPU S3C2440A (id 0x32440001)
S3C24XX Clocks, (c) 2004 Simtec Electronics
S3C244X: core 400.000 MHz, memory 100.000 MHz, peripheral 50.000 MHz
CLOCK: Slow mode (1.500 MHz), fast, MPLL on, UPLL on
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 16256
Kernel command line: noinitrd root=/dev/mtdblock2 init=/linuxrc console=ttySAC0
NR_IRQS:85
irq: clearing subpending status 00000002
PID hash table entries: 256 (order: 8, 1024 bytes)
Console: colour dummy device 80x30
console [ttySAC0] enabled
Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
Memory: 64MB = 64MB total
Memory: 60944KB available (3384K code, 311K data, 120K init, 0K highmem)
Calibrating delay loop... 199.47 BogoMIPS (lpj=498688)
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
net_namespace: 936 bytes
NET: Registered protocol family 16
S3C Power Management, Copyright 2004 Simtec Electronics
S3C2440: Initialising architecture
S3C2440: IRQ Support
S3C24XX DMA Driver, (c) 2003-2004,2006 Simtec Electronics
DMA channel 0 at c4808000, irq 33
DMA channel 1 at c4808040, irq 34
DMA channel 2 at c4808080, irq 35
DMA channel 3 at c48080c0, irq 36
S3C244X: Clock Support, DVS off
bio: create slab <bio-0> at 0
SCSI subsystem initialized
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
s3c2440-i2c s3c2440-i2c: slave address 0x10
s3c2440-i2c s3c2440-i2c: bus frequency set to 97 KHz
s3c2440-i2c s3c2440-i2c: i2c-0: S3C I2C adapter
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 2048 (order: 2, 16384 bytes)
TCP bind hash table entries: 2048 (order: 1, 8192 bytes)
TCP: Hash tables configured (established 2048 bind 2048)
TCP reno registered
NET: Registered protocol family 1
NetWinder Floating Point Emulator V0.97 (extended precision)
JFFS2 version 2.2. (NAND) (SUMMARY)  ?? 2001-2006 Red Hat, Inc.
ROMFS MTD (C) 2007 Red Hat, Inc.
msgmni has been set to 119
io scheduler noop registered
io scheduler anticipatory registered (default)
io scheduler deadline registered
io scheduler cfq registered
Console: switching to colour frame buffer device 30x40
fb0: s3c2410fb frame buffer device
lp: driver loaded but no devices found
ppdev: user-space parallel port driver
Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
s3c2440-uart.0: s3c2410_serial0 at MMIO 0x50000000 (irq = 70) is a S3C2440
s3c2440-uart.1: s3c2410_serial1 at MMIO 0x50004000 (irq = 73) is a S3C2440
s3c2440-uart.2: s3c2410_serial2 at MMIO 0x50008000 (irq = 76) is a S3C2440
brd: module loaded
loop: module loaded
Uniform Multi-Platform E-IDE driver
ide-gd driver 1.18
ide-cd driver 5.00
Driver ‘sd‘ needs updating - please use bus_type methods
dm9000 Ethernet Driver, V1.31
S3C24XX NAND Driver, (c) 2004 Simtec Electronics
s3c2440-nand s3c2440-nand: Tacls=3, 30ns Twrph0=7 70ns, Twrph1=3 30ns
NAND device: Manufacturer ID: 0xec, Chip ID: 0xda (Samsung NAND 256MiB 3,3V 8-bit)
Scanning device for bad blocks
Bad eraseblock 1153 at 0x000009020000
Creating 8 MTD partitions on "NAND 256MiB 3,3V 8-bit":
0x000000000000-0x000000004000 : "Boot Agent"
mtd: partition "Boot Agent" doesn‘t end on an erase block -- force read-only
0x000000000000-0x000000200000 : "S3C2410 flash partition 1"
0x000000400000-0x000000800000 : "S3C2410 flash partition 2"
0x000000800000-0x000000a00000 : "S3C2410 flash partition 3"
0x000000a00000-0x000000e00000 : "S3C2410 flash partition 4"
0x000000e00000-0x000001800000 : "S3C2410 flash partition 5"
0x000001800000-0x000003000000 : "S3C2410 flash partition 6"
0x000003000000-0x000004000000 : "S3C2410 flash partition 7"
usbmon: debugfs is not available
ohci_hcd: USB 1.1 ‘Open‘ Host Controller (OHCI) Driver
s3c2410-ohci s3c2410-ohci: S3C24XX OHCI
s3c2410-ohci s3c2410-ohci: new USB bus registered, assigned bus number 1
s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000
usb usb1: configuration #1 chosen from 1 choice
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
usbcore: registered new interface driver libusual
usbcore: registered new interface driver usbserial
USB Serial support registered for generic
usbcore: registered new interface driver usbserial_generic
usbserial: USB Serial Driver core
USB Serial support registered for FTDI USB Serial Device
usbcore: registered new interface driver ftdi_sio
ftdi_sio: v1.4.3:USB FTDI Serial Converters Driver
USB Serial support registered for pl2303
usbcore: registered new interface driver pl2303
pl2303: Prolific PL2303 USB to serial adaptor driver
mice: PS/2 mouse device common for all mice
S3C24XX RTC, (c) 2004,2006 Simtec Electronics
S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics
s3c2410-wdt s3c2410-wdt: watchdog inactive, reset disabled, irq enabled
Advanced Linux Sound Architecture Driver Version 1.0.20.
ALSA device list:
  No soundcards found.
TCP cubic registered
NET: Registered protocol family 17
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
drivers/rtc/hctosys.c: unable to open rtc device (rtc0)
List of all partitions:
1f00              16 mtdblock0 (driver?)
1f01            2048 mtdblock1 (driver?)
1f02            4096 mtdblock2 (driver?)
1f03            2048 mtdblock3 (driver?)
1f04            4096 mtdblock4 (driver?)
1f05           10240 mtdblock5 (driver?)
1f06           24576 mtdblock6 (driver?)
1f07           16384 mtdblock7 (driver?)
No filesystem could mount root, tried:  ext3 ext2 cramfs vfat msdos iso9660 romfs
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(31,2)
[<c002c700>] (unwind_backtrace+0x0/0xdc) from [<c02a6d24>] (panic+0x40/0x110)
[<c02a6d24>] (panic+0x40/0x110) from [<c0008fcc>] (mount_block_root+0x1d0/0x210)
[<c0008fcc>] (mount_block_root+0x1d0/0x210) from [<c0009264>] (prepare_namespace+0x164/0x1bc)
[<c0009264>] (prepare_namespace+0x164/0x1bc) from [<c0008598>] (kernel_init+0xb4/0xe0)
[<c0008598>] (kernel_init+0xb4/0xe0) from [<c004814c>] (do_exit+0x0/0x578)
[<c004814c>] (do_exit+0x0/0x578) from [<00000001>] (0x1)

由于还没有烧入文件系统且kernel设置的分区也不正确，所以跑到fs就挂住了，可参考后篇博文关于搭建文件系统 《嵌入式学习笔记300-linux根文件系统搭建》