sd card data broken after umount

Question

I wrote an SD host-controller Linux driver for a totally customized board, using IP TE4395.

With the driver I wrote,

I can mount an SD card, read and write.
when mounted, once I umount, the next mount will fail.
command mount -o remount /dev/mmcblk0p1 worked normally....

# ls /mnt/
aaa.txt     lost+found
# mount -o remount /dev/mmcblk0p1
EXT4-fs (mmcblk0p1): re-mounted. Opts: block_validity,delalloc,barrier,user_xattr,acl
# echo adfaf >/mnt/bbb.txt
# ls /mnt/
aaa.txt     bbb.txt     lost+found
# cat /mnt/bbb.txt
adfaf
# sync
# ls /mnt/
aaa.txt     bbb.txt     lost+found
# umount /mnt/
# mount /dev/mmcblk0p1 /mnt
mount: mounting /dev/mmcblk0p1 on /mnt failed: Invalid argument

Is there an entry for /dev/mmcblk0p1 in your `fstab`? What happens if you try and specify the filesystem and options explicitly? — mikemaccana, Aug 30 '16 at 07:51
I tried, the result is same `mount /dev/mmcblk0p1 /mnt -t ext2`. and there is no entry for /dev/mmcblk0p1 in fstab — jianing, Aug 30 '16 at 08:03
no, after unmount, the card's superblock just be broken. I tried to mount in a desktop linux, the filesystem cannot be recognized. — jianing, Aug 31 '16 at 00:12

score 0 · Answer 1 · answered Sep 02 '16 at 06:32

I know the reason. the driver has a problem. I added some code for debug, that read register when driver write registers. And the Data Port register is special, when access the register the buffer pointer inside the controller will be incremented automatically. The debug code read before and after write to the register, so accessed the register 3 times, but expected just 1 time access(write).

sd card data broken after umount

1 Answers1