sfa18 # help
?       - alias for 'help'
base    - print or set address offset
bdinfo  - print Board Info structure
boot    - boot default, i.e., run 'bootcmd'
bootd   - boot default, i.e., run 'bootcmd'
bootelf - Boot from an ELF image in memory
bootm   - boot application image from memory
bootp   - boot image via network using BOOTP/TFTP protocol
bootvx  - Boot vxWorks from an ELF image
cmp     - memory compare
coninfo - print console devices and information
cp      - memory copy
crc32   - checksum calculation
date    - get/set/reset date & time
dhcp    - boot image via network using DHCP/TFTP protocol
dm      - Driver model low level access
echo    - echo args to console
editenv - edit environment variable
env     - environment handling commands
exit    - exit script
false   - do nothing, unsuccessfully
fdt     - flattened device tree utility commands
go      - start application at address 'addr'
help    - print command description/usage
httpd   - start www server for firmware recovery with [localAddress]

iminfo  - print header information for application image
imxtract- extract a part of a multi-image
itest   - return true/false on integer compare
loop    - infinite loop on address range
lzmadec - lzma uncompress a memory region
md      - memory display
mm      - memory modify (auto-incrementing address)
mmc     - MMC sub system
mmcinfo - display MMC info
mw      - memory write (fill)
nm      - memory modify (constant address)
ping    - send ICMP ECHO_REQUEST to network host
printenv- print environment variables
reset   - Perform RESET of the CPU
run     - run commands in an environment variable
saveenv - save environment variables to persistent storage
setenv  - set environment variables
sf      - SPI flash sub-system
showvar - print local hushshell variables
sleep   - delay execution for some time
source  - run script from memory
spld    - update spl from device
test    - minimal test like /bin/sh
tftpboot- boot image via network using TFTP protocol
true    - do nothing, successfully
version - print monitor, compiler and linker version

sfa18 # env print -a
baudrate=115200
bootcmd=sf probe 0 33000000;sf read 0x81000000 0xa0000 0xa00000;bootm
bootdelay=2
ethact=sf_eth0
fdtcontroladdr=8fe9d57c
stderr=serial@8300000
stdin=serial@8300000
stdout=serial@8300000

Environment size: 219/65532 bytes

sfa18 # setenv efuse_data aabbccdd
sfa18 # printenv efuse_data 
efuse_data=aabbccdd

sfa18 # help sf
sf - SPI flash sub-system
Usage:
sf probe [[bus:]cs] [hz] [mode] - init flash device on given SPI bus
                                  and chip select
sf read addr offset|partition len       - read `len' bytes starting at
                                          `offset' or from start of mtd
                                          `partition'to memory at `addr'
sf write addr offset|partition len      - write `len' bytes from memory
                                          at `addr' to flash at `offset'
                                          or to start of mtd `partition'
sf erase offset|partition [+]len        - erase `len' bytes from `offset'
                                          or from start of mtd `partition'
                                         `+len' round up `len' to block size
sf update addr offset|partition len     - erase and write `len' bytes from memory
                                          at `addr' to flash at `offset'
                                          or to start of mtd `partition'
sf protect lock/unlock sector len       - protect/unprotect 'len' bytes starting
                                          at address 'sector'
sfa18 #

sfa18 # sf probe 0 33000000
do_spi_flash----cmd = probe
SF: Detected W25Q128BV with page size 256 Bytes, erase size 4 KiB, total 16 MiB
sfa18 # sf read 0x81000000 0xa0000 0xa00000
do_spi_flash----cmd = read
device 0 offset 0xa0000, size 0xa00000
SF: 10485760 bytes @ 0xa0000 Read: OK
sfa18 # 

sfa18 # help bootm
bootm - boot application image from memory

Usage:
bootm [addr [arg ...]]
    - boot application image stored in memory
        passing arguments 'arg ...'; when booting a Linux kernel,
        'arg' can be the address of an initrd image
        When booting a Linux kernel which requires a flat device-tree
        a third argument is required which is the address of the
        device-tree blob. To boot that kernel without an initrd image,
        use a '-' for the second argument. If you do not pass a third
        a bd_info struct will be passed instead

Sub-commands to do part of the bootm sequence.  The sub-commands must be
issued in the order below (it's ok to not issue all sub-commands):
        start [addr [arg ...]]
        loados  - load OS image
        ramdisk - relocate initrd, set env initrd_start/initrd_end
        fdt     - relocate flat device tree
        cmdline - OS specific command line processing/setup
        bdt     - OS specific bd_t processing
        prep    - OS specific prep before relocation or go
        go      - start OS
sfa18 # 

sfa18 # bootm
## Booting kernel from Legacy Image at 81000000 ...
   Image Name:   MIPS OpenWrt Linux-3.18.29
   Created:      2017-08-31   6:27:49 UTC
   Image Type:   MIPS Linux Kernel Image (lzma compressed)
   Data Size:    1635008 Bytes = 1.6 MiB
   Load Address: 80100000
   Entry Point:  80105360
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK

./sf_make.sh ver=fullmask

./sf_make.sh cmd=clean  

./make.sh sfa28_evb 

[ -z $ddr3 ] && ddr3=ddr3_1gcommon

[ -z $ddr3 ] &&; ddr3=ddr3_2gcommon

[ -z $ddr2 ] && ddr2=ddr2_512mcommon

[ -z $ddr2 ] &&; ddr2=ddr2_1gcommon

#define msleep(a)      udelay(a * 1000)
#define ssleep(a)      msleep(a * 1000)
/* We come here after U-Boot is initialised and ready to process commands */
#include <asm/gpio.h>
void main_loop(void)
{
        const char *s; 

        if (gpio_request(12, "sf_gpio")) {  //申请GPIO
                        printf("Failed to request gpio %d\n",12);
        }
        if (gpio_direction_output(12,1)) {  //配置GPIO输入/输出
                                   printf("Failed to set gpio value %d\n",12);
        }
        for (;;) {
                msleep(1000);
                gpio_set_value(12,0);     //设置GPIO高低电平
                msleep(1000);
                gpio_set_value(12,1);
        }
        gpio_free(12);
        bootstage_mark_name(BOOTSTAGE_ID_MAIN_LOOP, "main_loop");

#ifdef CONFIG_VERSION_VARIABLE
        setenv("ver", version_string);  /* set version variable */
#endif /* CONFIG_VERSION_VARIABLE */

        cli_init();

        run_preboot_environment_command();
..
...
....
}