STM32F746-DISCO運行Linux4.19

STM32F746-DISCO運行Linux4.19

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Linux Kernel

主線linux已經提供對無MMU的處理器的支持，configs中已經存在stm32_defconfig，DTS中包含：stm32f746-disco；所以只須要編譯便可。
下載主線源碼:http://cdn.kernel.org/pub/linux/kernel/v4.x
安裝交叉編譯鏈，可使用以前編譯uboot的arm-none-eabi-gcc，可是這個是編譯鏈線程模式是single，而不是posix，也就是說雖然這個編譯鏈能夠編譯內核和根文件系統，可是不能編譯linux應用程序。若是須要支持編譯linux應用程序（通常要支持，否則移植linux幹嗎--！），則須要本身去構建交叉編譯鏈，網上講解的比較詳細，不過我推薦使用Buildroot來構建支持stm32的交叉編譯鏈，簡單快捷，固然也能夠用Buildroot來構建內核和根文件系統。

根文件系統

根文件系統可使用busybox構建，也可使用buildroot構建。
elinux.org提供了一個使用busybox編譯好的Ramdisk最小系統，File:Stm32 mini rootfs.cpio.bz2, 但須要作以下改動：
使用initramfs，將下載的Stm32_mini_rootfs.cpio.bz2解壓，先解壓成cpio文件：
bzip2 -d Stm32_mini_rootfs.cpio.bz2
建立文件夾rootfs：
mkdir rootfs
將文件解壓到rootfs文件夾中：
cpio -idmv <../Stm32_mini_rootfs.cpio
看看dev中是否有null，tty0，console節點，沒有的話須要在dev文件夾中建立這三個節點。

sudo mknod console c 5 1 
sudo mknod null c 1 3 
sudo mknod tty0 c 204 64

再rootfs文件夾下新建init文件，內容以下

#!/bin/sh # devtmpfs does not get automounted for initramfs /bin/mount -t devtmpfs devtmpfs /dev exec 0/dev/console exec 2>/dev/console exec /sbin/init $

配置內核使用initramfs
make ARCH=arm CROSS_COMPILE=arm-none-eabi- menuconfig

[*] Initial RAM filesystem and RAM disk (initramfs/initrd) support  
    (/work/system/my-linux/rootfs) Initramfs source file(s)

上述步驟主要參考了這位老哥的實現，https://blog.csdn.net/u011371090/article/details/81587170
若是須要使用其餘類型的根文件系統，好比ext4等，須要修改bootcmd，具體再研究。

編譯過程

make ARCH=arm CROSS_COMPILE=arm-none-eabi- stm32_defconfig 
make mkimage -n 'linux' -A arm -O linux -T kernel -C none -a 0xc0300000 -e 0xc0300000 -d ./arch/arm/boot/zImage uImage

UBOOT命令行手動下載，引導

setenv ipaddr 192.168.66.69 
setenv serverip 192.168.66.66 
tftp c0300000 uImage 
tftp c0500000 stm32f746-disco.dtb 
setenv bootargs "root=/dev/ram console=ttySTM0,115200"  
bootm c0300000 - c0500000

UBOOT手動下載kernel至spi flash中

sf probe 
sf erase 0 1000000 
sf write c0300000 0 200000 
sf write c0500000 200000 4000

UBOOT設置自動從spi flash中引導

能夠更改源碼將bootcmd寫入源碼中，否則每次都要手動改。

setenv bootcmd "setenv bootargs "root=/dev/ram console=ttySTM0,115200"; sf probe; sf read c0300000 0 200000;sf read c0500000 200000 4000;bootm c0300000 - c0500000;"

啓動日誌

U-Boot > env set bootargs "root=/dev/ram console=ttySTM0,115200"
U-Boot > bootm c0300000 - c0500000
## Booting kernel from Legacy Image at c0300000 ...
   Image Name:   linux
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1519384 Bytes = 1.4 MiB
   Load Address: c0300000
   Entry Point:  c0300000
   Verifying Checksum ... OK
## Flattened Device Tree blob at c0500000
   Booting using the fdt blob at 0xc0500000
   Loading Kernel Image ... OK
   Using Device Tree in place at c0500000, end c0506a09

Starting kernel ...

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 4.19.69 (yhang@localhost.localdomain) (gcc version 7.3.1 20180622 (release) [ARM/embedded-7-branch revision 261907] (GNU Tools for Arm Embedded Processors 7-2018-q2-update)) #1 PREEMPT Thu Sep 5 09:03:24 CST 2019
[    0.000000] CPU: ARMv7-M [410fc271] revision 1 (ARMv7M), cr=00000000
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
[    0.000000] OF: fdt: Machine model: STMicroelectronics STM32F746-DISCO board
[    0.000000] random: get_random_bytes called from start_kernel+0x55/0x2c8 with crng_init=0
[    0.000000] Built 1 zonelists, mobility grouping off.  Total pages: 2032
[    0.000000] Kernel command line: root=/dev/ram console=ttySTM0,115200
[    0.000000] Dentry cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.000000] Inode-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.000000] Memory: 5508K/8192K available (1479K kernel code, 142K rwdata, 472K rodata, 216K init, 115K bss, 2684K reserved, 0K cma-reserved)
[    0.000000] Virtual kernel memory layout:
[    0.000000]     vector  : 0x00000000 - 0x00001000   (   4 kB)
[    0.000000]     fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)
[    0.000000]     vmalloc : 0x00000000 - 0xffffffff   (4095 MB)
[    0.000000]     lowmem  : 0xc0000000 - 0xc0800000   (   8 MB)
[    0.000000]       .text : 0x(ptrval) - 0x(ptrval)   (1480 kB)
[    0.000000]       .init : 0x(ptrval) - 0x(ptrval)   ( 216 kB)
[    0.000000]       .data : 0x(ptrval) - 0x(ptrval)   ( 143 kB)
[    0.000000]        .bss : 0x(ptrval) - 0x(ptrval)   ( 116 kB)
[    0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[    0.000000] rcu: Preemptible hierarchical RCU implementation.
[    0.000000]  Tasks RCU enabled.
[    0.000000] NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
[    0.000000] interrupt-controller@40013c00: bank0, External IRQs available:0xffffff
[    0.000000] clocksource: arm_system_timer: mask: 0xffffff max_cycles: 0xffffff, max_idle_ns: 298634427 ns
[    0.000000] ARM System timer initialized as clocksource
[    0.000067] sched_clock: 32 bits at 100MHz, resolution 10ns, wraps every 21474836475ns
[    0.000154] timer@40000c00: STM32 sched_clock registered
[    0.000250] Switching to timer-based delay loop, resolution 10ns
[    0.000322] timer@40000c00: STM32 delay timer registered
[    0.000434] clocksource: timer@40000c00: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604467 ns
[    0.000592] /soc/timer@40000c00: STM32 clockevent driver initialized (32 bits)
[    0.001473] Calibrating delay loop (skipped), value calculated using timer frequency.. 200.00 BogoMIPS (lpj=1000000)
[    0.001635] pid_max: default: 4096 minimum: 301
[    0.002945] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.003100] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.012600] rcu: Hierarchical SRCU implementation.
[    0.017399] devtmpfs: initialized
[    0.069578] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.069719] pinctrl core: initialized pinctrl subsystem
[    0.108491] stm32f746-pinctrl soc:pin-controller: GPIOA bank added
[    0.110059] stm32f746-pinctrl soc:pin-controller: GPIOB bank added
[    0.111741] stm32f746-pinctrl soc:pin-controller: GPIOC bank added
[    0.113419] stm32f746-pinctrl soc:pin-controller: GPIOD bank added
[    0.114960] stm32f746-pinctrl soc:pin-controller: GPIOE bank added
[    0.116526] stm32f746-pinctrl soc:pin-controller: GPIOF bank added
[    0.118141] stm32f746-pinctrl soc:pin-controller: GPIOG bank added
[    0.119682] stm32f746-pinctrl soc:pin-controller: GPIOH bank added
[    0.121218] stm32f746-pinctrl soc:pin-controller: GPIOI bank added
[    0.123182] stm32f746-pinctrl soc:pin-controller: GPIOJ bank added
[    0.124780] stm32f746-pinctrl soc:pin-controller: GPIOK bank added
[    0.124952] stm32f746-pinctrl soc:pin-controller: Pinctrl STM32 initialized
[    0.167396] clocksource: Switched to clocksource timer@40000c00
[    0.286124] workingset: timestamp_bits=30 max_order=11 bucket_order=0
[    0.355551] io scheduler noop registered (default)
[    0.355664] io scheduler mq-deadline registered
[    0.355753] io scheduler kyber registered
[    0.359175] STM32 USART driver initialized
[    0.360584] 40011000.serial: ttySTM0 at MMIO 0x40011000 (irq = 33, base_baud = 6250000) is a stm32-usart
[    0.757352] console [ttySTM0] enabled
[    0.763214] stm32-usart 40011000.serial: rx dma alloc failed
[    0.769230] stm32-usart 40011000.serial: interrupt mode used for rx (no dma)
[    0.776229] stm32-usart 40011000.serial: tx dma alloc failed
[    0.782067] stm32-usart 40011000.serial: interrupt mode used for tx (no dma)
[    0.792438] i2c /dev entries driver
[    0.843743] stm32f7-i2c 40005400.i2c: can't use DMA
[    0.851160] stm32f7-i2c 40005400.i2c: STM32F7 I2C-0 bus adapter
[    0.862408] mmci-pl18x 40012c00.sdio1: Got CD GPIO
[    0.868031] mmci-pl18x 40012c00.sdio1: Linked as a consumer to regulator.2
[    0.875138] mmci-pl18x 40012c00.sdio1: mmc0: PL180 manf 80 rev8 at 0x40012c00 irq 34,0 (pio)
[    0.883767] mmci-pl18x 40012c00.sdio1: DMA channels RX none, TX none
[    0.928369] hctosys: unable to open rtc device (rtc0)
[    0.935401] mmc_vcard: disabling
[    0.941700] Freeing unused kernel memory: 216K
[    0.946045] This architecture does not have kernel memory protection.
[    0.952691] Run /init as init process