Hi, we've been using a new SD card for 6+ months without issues, but recently noticed issues with newer releases. I'm not sure if it's the SD cards, our burner stations or our build process. Were using U-Boot 2014.07

The problem is that we can't read/write to the SD card during boot. This happens intermittently on freshly burned cards. 75% of the time it works.

Our bootcmd starts with ext2load mmc ... but obviously it fails due to "can't read partition table".

Manually debugging in U-Boot if I run mmc rescan then it can read the partition table, but if I reboot the system then the issue comes back upon next power-up.

If I run rescan AND then saveenv then everything works after that.

My questions are:

1. Is it good practice to run mmc rescan as one of the first things in bootcmd?

2. I'm a little confised as to why saveenv would cause the SD card to work again *persistently*.

3. Any recommendations on getting root cause as to what it could be (SD card, our burner stations or our build process)?

Troubleshooting steps below...

MX51 U-Boot > mmc info Device: FSL_SDHC Manufacturer ID: 87 OEM: 494f Name: 004GB Tran Speed: 50000000 Rd Block Len: 512 SD version 3.0 High Capacity: Yes Capacity: 3.8 GiB Bus Width: 1-bit MX51 U-Boot > mmc part

Partition Map for MMC device 0 -- Partition Type: DOS

Part Start Sector Num Sectors UUID Type ** Can't read partition table on 0:0 ** MX51 U-Boot > mmc rescan MX51 U-Boot > mmc part

Partition Map for MMC device 0 -- Partition Type: DOS

Part Start Sector Num Sectors UUID Type 1 31000 3844000 00000000-01 83 2 3882750 4037750 00000000-02 83 MX51 U-Boot > saveenv Saving Environment to MMC...

reboot and everything works.

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