https://becomwiki.live.md-websolutions.com/index.php?action=history&feed=atom&title=SD_controller_%28CM-i.MX27%29SD controller (CM-i.MX27) - Versionsgeschichte2026-05-13T12:46:04ZVersionsgeschichte dieser Seite in BECOM Systems SupportMediaWiki 1.43.5https://becomwiki.live.md-websolutions.com/index.php?title=SD_controller_(CM-i.MX27)&diff=352&oldid=prevPeter: 1 Version importiert2023-10-31T08:03:09Z<p>1 Version importiert</p>
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</td></tr></table>Peterhttps://becomwiki.live.md-websolutions.com/index.php?title=SD_controller_(CM-i.MX27)&diff=351&oldid=preven>Peter: 1 Version importiert2023-08-22T19:35:52Z<p>1 Version importiert</p>
<p><b>Neue Seite</b></p><div>The i.MX27 contains an SD host controller that supports MMC, SD and SD I/O standards.<br />
SDHC1 of the processor is connected to the SD cards lot on the DEV board.<br />
<br />
== Linux kernel configuration ==<br />
<br />
Device Drivers ---><br />
<*> MMC/SD card support ---><br />
<*> MMC block device driver<br />
[*] Use bounce buffer for simple hosts<br />
<*> Freescale MXC Multimedia Card Interface support<br />
<br />
== Test in Linux ==<br />
<br />
*Insert an SD card into the slot on the DEV board. You will see similar messages on the terminal:<br />
root@btmxc27:~# mmc0: host does not support reading read-only switch. assuming write-enable.<br />
mmc0: new SD card at address fcd9<br />
mmcblk0: mmc0:fcd9 SD02G 1985024KiB <br />
mmcblk0:<br />
FAT: bogus number of reserved sectors<br />
VFS: Can't find a valid FAT filesystem on dev mmcblk0.<br />
<br />
*We will now start ''fdisk'' and create 1 partition on the card that uses up the full available space:<br />
root@btmxc27:~# fdisk /dev/mmcblk0 <br />
<br />
The number of cylinders for this disk is set to 62032.<br />
There is nothing wrong with that, but this is larger than 1024,<br />
and could in certain setups cause problems with:<br />
1) software that runs at boot time (e.g., old versions of LILO)<br />
2) booting and partitioning software from other OSs<br />
(e.g., DOS FDISK, OS/2 FDISK)<br />
<br />
Command (m for help): p<br />
<br />
Disk /dev/mmcblk0: 2032 MB, 2032664576 bytes<br />
4 heads, 16 sectors/track, 62032 cylinders<br />
Units = cylinders of 64 * 512 = 32768 bytes<br />
<br />
Device Boot Start End Blocks Id System<br />
<br />
Command (m for help): n<br />
Command action<br />
e extended<br />
p primary partition (1-4)<br />
p<br />
Partition number (1-4): 1<br />
First cylinder (1-62032, default 1): Using default value 1<br />
Last cylinder or +size or +sizeM or +sizeK (1-62032, default 62032): Using default value 62032<br />
<br />
Command (m for help): p<br />
<br />
Disk /dev/mmcblk0: 2032 MB, 2032664576 bytes<br />
4 heads, 16 sectors/track, 62032 cylinders<br />
Units = cylinders of 64 * 512 = 32768 bytes<br />
<br />
Device Boot Start End Blocks Id System<br />
/dev/mmcblk0p1 1 62032 1985016 83 Linux<br />
<br />
Command (m for help): w<br />
The partition table has been altered!<br />
<br />
Calling ioctl() to re-read partition table<br />
mmcblk0: p1<br />
root@btmxc27:~# FAT: bogus number of reserved sectors<br />
VFS: Can't find a valid FAT filesystem on dev mmcblk0p1.<br />
<br />
* Now we will create an ''ext3'' file system in this partition:<br />
<br />
root@btmxc27:~# mkfs.ext3 /dev/mmcblk0p1 <br />
mke2fs 1.41.4 (27-Jan-2009)<br />
Filesystem label=<br />
OS type: Linux<br />
Block size=4096 (log=2)<br />
Fragment size=4096 (log=2)<br />
124160 inodes, 496254 blocks<br />
24812 blocks (5.00%) reserved for the super user<br />
First data block=0<br />
Maximum filesystem blocks=511705088<br />
16 block groups<br />
32768 blocks per group, 32768 fragments per group<br />
7760 inodes per group<br />
Superblock backups stored on blocks: <br />
32768, 98304, 163840, 229376, 294912<br />
<br />
Writing inode tables: done <br />
Creating journal (8192 blocks): done<br />
Writing superblocks and filesystem accounting information: done<br />
<br />
This filesystem will be automatically checked every 26 mounts or<br />
180 days, whichever comes first. Use tune2fs -c or -i to override.<br />
<br />
*Mount the SD card (first partition) to ''/media/card''. Numbering of mmc block devices and partitions is '''mmcblk'''[card_nr]'''p'''[partition_nr], where the first possible ''card_nr'' is 0 and the first possible ''partition_nr'' is 1.<br />
<br />
root@btmxc27:~# mount /dev/mmcblk0p1 /media/card/<br />
kjournald starting. Commit interval 5 seconds<br />
EXT3 FS on mmcblk0p1, internal journal<br />
EXT3-fs: mounted filesystem with ordered data mode.<br />
<br />
*For measuring the performance, we will transfer a file from RAM to the SD card. Therefore, we also create an ''ext3'' file system on the ram disk:<br />
root@btmxc27:~# mkfs.ext3 /dev/ram0 <br />
mke2fs 1.41.4 (27-Jan-2009)<br />
Filesystem label=<br />
OS type: Linux<br />
Block size=1024 (log=0)<br />
Fragment size=1024 (log=0)<br />
16384 inodes, 65536 blocks<br />
3276 blocks (5.00%) reserved for the super user<br />
First data block=1<br />
Maximum filesystem blocks=67108864<br />
8 block groups<br />
8192 blocks per group, 8192 fragments per group<br />
2048 inodes per group<br />
Superblock backups stored on blocks: <br />
8193, 24577, 40961, 57345<br />
<br />
Writing inode tables: done <br />
Creating journal (4096 blocks): done<br />
Writing superblocks and filesystem accounting information: done<br />
<br />
This filesystem will be automatically checked every 23 mounts or<br />
180 days, whichever comes first. Use tune2fs -c or -i to override.<br />
<br />
*...and mount it to ''/media/ram'':<br />
root@btmxc27:~# mount /dev/ram0 /media/ram/<br />
kjournald starting. Commit interval 5 seconds<br />
EXT3 FS on ram0, internal journal<br />
EXT3-fs: mounted filesystem with ordered data mode.<br />
<br />
*Now we change to this directory and download a random file of 32 MiB size:<br />
root@btmxc27:~# cd /media/ram/<br />
root@btmxc27:/media/ram# tftp -r 32MBrandomfile -g 192.168.5.1<br />
root@btmxc27:/media/ram# ls<br />
32MBrandomfile lost+found<br />
<br />
*Let's transfer this file to the SD card and measure the time. The complete time can be calculated by adding both "real" times.<br />
root@btmxc27:/media/ram# cd /media/card/<br />
root@btmxc27:/media/card# ls<br />
lost+found<br />
root@btmxc27:/media/card# cd /<br />
root@btmxc27:/# time cp /media/ram/32MBrandomfile /media/card/ ; time umount /me<br />
dia/card/<br />
real 0m 10.72s<br />
user 0m 0.10s<br />
sys 0m 5.41s<br />
real 0m 5.97s<br />
user 0m 0.00s<br />
sys 0m 0.40s<br />
<br />
*To measure read performance, we mount the SD card again and read the 32 MiB file to ''/dev/null'' (i.e., nowhere).<br />
root@btmxc27:/# mount /dev/mmcblk0p1 /media/card/<br />
kjournald starting. Commit interval 5 seconds<br />
EXT3 FS on mmcblk0p1, internal journal<br />
EXT3-fs: mounted filesystem with ordered data mode.<br />
root@btmxc27:/# time cat /media/card/32MBrandomfile > /dev/null ; time umount /m<br />
edia/card/<br />
real 0m 9.51s<br />
user 0m 0.02s<br />
sys 0m 1.40s<br />
real 0m 0.08s<br />
user 0m 0.01s<br />
sys 0m 0.04s<br />
root@btmxc27:/#<br />
<br />
*To check if the data was written correctly, you may check the ''md5sum''s of both files:<br />
root@btmxc27:/# md5sum /media/ram/32MBrandomfile <br />
f507996f89cd0d6ff3f5e0edcf5aa0a1 /media/ram/32MBrandomfile<br />
root@btmxc27:/# md5sum /media/card/32MBrandomfile <br />
f507996f89cd0d6ff3f5e0edcf5aa0a1 /media/card/32MBrandomfile<br />
<br />
<br />
== Performance ==<br />
<br />
Measured in Linux, using a ''SanDisk Extreme III 2.0GB'' card:<br />
*Write: 1.92 MiB/s<br />
*Read: 3.34 MiB/s<br />
<br />
== Remarks ==<br />
<br />
* If you remove the card very slowly, the removal may not be detected correctly.<br />
<br />
At removal, the CD (card detect) IRQ is triggered. But at this time, the SD card<br />
is yet readable and the MMC driver does not detect the removal. We have increased<br />
the wait time from IRQ to checking for removal to 1 second. If you are<br />
extremely slow at removing the card, the removal may not be detected<br />
correctly, though.<br />
<br />
* Don't enable CONFIG_DEBUG_SHIRQ in your kernel configuration. The SD Card will refuse to work!<br />
<br />
<br />
[[Category:i.MX27]]</div>en>Peter