从emmc启动uboot后，无法识别emmc

huojusan

操作步骤：
1. 制作SD卡启动uboot，从野火提供的git路径clone下来编译的uboot
2. sd启动uboot功能正常，也能保存环境参数，操作mmc命令
3. 通过tftp将ubuntu编译的emmc启动的uboot下载到开发板内存
4. 通过mmc命令将内存中的uboot烧写到emmc
5. 拔掉sd卡，设置从emmc启动，启动打印信息如下
6. 在emmc启动uboot后，无法识别emmc，只能识别sd

问题描述：
从emmc启动uboot后，却无法识别emmc，如果插上SD卡，是可以识别的

1. <p>U-Boot 2016.03 (Feb 06 2020 - 12:46:08 +0800)</p><p>
   
2. </p><p>CPU:   Freescale i.MX6ULL rev1.1 69 MHz (running at 396 MHz)</p><p>CPU:   Industrial temperature grade (-40C to 105C) at 40C</p><p>Reset cause: POR</p><p>Board: MX6ULL 14x14 EVK</p><p>I2C:   ready</p><p>DRAM:  512 MiB</p><p>
   
3. </p><p>MMC:   FSL_SDHC: 0, FSL_SDHC: 1</p><p>
   
4. </p><p>*** Warning - bad CRC, using default environment</p><p>
   
5. </p><p>In:    serial</p><p>Out:   serial</p><p>Err:   serial</p><p>MMC: no card present</p><p>Net:   FEC1</p><p>Error: FEC1 address not set.</p><p>
   
6. </p><p>Normal Boot</p><p>Hit any key to stop autoboot:  3 </p><p>=> mmc list</p><p>FSL_SDHC: 0</p><p>FSL_SDHC: 1</p><p>=> mmc dev 1</p><p>MMC: no card present</p><p>=> mmc dev 0</p><p>[08:35:27.152]收←◆switch to partitions #0, OK</p><p>mmc0 is current device</p><p>=> </p>

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huojusan

1. U-Boot 2016.03 (Feb 06 2020 - 12:46:08 +0800)
   
2. 
   
3. CPU:   Freescale i.MX6ULL rev1.1 69 MHz (running at 396 MHz)
   
4. CPU:   Industrial temperature grade (-40C to 105C) at 40C
   
5. Reset cause: POR
   
6. Board: MX6ULL 14x14 EVK
   
7. I2C:   ready
   
8. DRAM:  512 MiB
   
9. 
   
10. MMC:   FSL_SDHC: 0, FSL_SDHC: 1
    
11. 
    
12. *** Warning - bad CRC, using default environment
    
13. 
    
14. In:    serial
    
15. Out:   serial
    
16. Err:   serial
    
17. MMC: no card present
    
18. Net:   FEC1
    
19. Error: FEC1 address not set.
    
20. 
    
21. Normal Boot
    
22. Hit any key to stop autoboot:  3
    
23. => mmc list
    
24. FSL_SDHC: 0
    
25. FSL_SDHC: 1
    
26. => mmc dev 1
    
27. MMC: no card present
    
28. => mmc dev 0
    
29. [08:35:27.152]收←◆switch to partitions #0, OK
    
30. mmc0 is current device
    
31. =>

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huojusan

1. => mmc info
   
2. 
   
3. [08:48:56.539]收←◆mmc info
   
4. Device: FSL_SDHC
   
5. Manufacturer ID: 0
   
6. OEM: 3432
   
7. Name: SD16G
   
8. Tran Speed: 50000000
   
9. Rd Block Len: 512
   
10. SD version 3.0
    
11. High Capacity: Yes
    
12. Capacity: 29.2 GiB
    
13. Bus Width: 4-bit
    
14. Erase Group Size: 512 Bytes
    
15. =>

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这是查看mmc信息打印结果