View source for Prepare a bootable NAND/eMMC

The purpose of this tutorial is to show how to flash a complete linux (u-boot + kernel + rootfs) into the internal storage of the system.

This steps has to be followed inside a board running a Linux from a external interface.

{| class="contenttable sortable"
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| style="border-color: #ffb521;"|'''<span class="note"><u>Note</u>:</span> you will need to boot from an SD or NFS in order to use an existing Linux to flash the new one.'''
|}

==Prepare the files==
First, it will be needed to prepare the following elements:

* u-boot or X-loader '''MLO''' and '''.img''' (in the case of i.mx chips both are together in a .imx file)
* '''zImage''' with the corresponfing kernel
* Correct '''.dtb''' used by this kernel
* '''rootfs''' with the corresponding modules installed all compressed in a''' .tar.bz2''' file.


==Flash into NAND (Tesdted with am335x based procesor)==
'''{{Message/Information Message|message=This steps has been followed using a Linux Kernel 4.9 and a IGEP SMARC MODULE AM335x}}'''

First, we will start with the case of using a NAND flash as internal storage.

{| class="contenttable sortable"
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| style="border-color: #ffb521;"|'''<span class="note"><u>Note</u>:</span>''' '''it will be used some special tools collected in the Mtdutils package. More info here: [http://jira.isee.biz:8090/display/LINUX/Mtdutils Mtdutils]'''
|}

It is recommendable to test the NAND flash and its partitions:

 nandtest -m /dev/mtd0<br data-attributes="%20/">nandtest -m /dev/mtd1<br data-attributes="%20/">nandtest -m /dev/mtd2<br data-attributes="%20/">nandtest -m /dev/mtd3
Then we erase the partitions:

 flash_eraseall /dev/mtd0<br data-attributes="%20/">flash_eraseall /dev/mtd1<br data-attributes="%20/">flash_eraseall /dev/mtd2<br data-attributes="%20/">flash_eraseall /dev/mtd3
Now we can flash the MLO in the first partition '''/dev/mtd0'''. It important to know that in this case (because it is a NAND flash and we have to record the MLO) we have to flash it four times in the first 4 blocks of this partition. In order to know the exact addresses we can check the documentation of the chip developer (in this case: [http://jira.isee.biz:8090/pages/viewpage.action?pageId=6619137 AM335x U-Boot User's Guide (Texas Documentation)] <span class="mw-headline">'''NAND Layout'''</span>) and will get the offset addresses '''[0x0 0x20000 0x40000 0x60000]''' . For each one of this addresses we have to write:

<pre>nandwrite -p -s [address] /dev/mtd0 [your_MLO]</pre>

For example:

 nandwrite -p -s 0x0 /dev/mtd0 /home/root/flash_files/MLO<br data-attributes="%20/">nandwrite -p -s 0x20000 /dev/mtd0 /home/root/flash_files/MLO<br data-attributes="%20/">nandwrite -p -s 0x40000 /dev/mtd0 /home/root/flash_files/MLO<br data-attributes="%20/">nandwrite -p -s 0x60000 /dev/mtd0 /home/root/flash_files/MLO

Then we will flash into the second partition '''/dev/mtd1''' the u-boot.img:

<pre>nandwrite -p /dev/mtd1 [your_u-boot.img]</pre>

For example:

 nandwrite -p /dev/mtd1 /home/root/flash_files/u-boot.img

In order to flash the rootfs we use the [https://en.wikipedia.org/wiki/UBIFS UBIFS] (<span class="mw-redirect">filesystem</span> for unmanaged flash memory devices) in the last partition '''/dev/mtd3'''. We are using a UBIFS in order to do it:]]

{| class="contenttable sortable"
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| style="border-color: #ffb521;"| '''<u>Note</u>: In this case we skip the third partiton /dev/mtd2 that is prepared to include if it is needed a environment uEnv.txt'''
|}<div class="confluence-information-macro-body"></div>
 ubiformat /dev/mtd3<br data-attributes="%20/">ubiattach -p /dev/mtd3<br data-attributes="%20/">ubimkvol /dev/ubi0 -N filesystem -m

Then, we can flash the rootfs:

 mkdir /tmp/flashroot<br data-attributes="%20/">mount -t ubifs ubi0:rootfs /tmp/flashroot/<br data-attributes="%20/">cd /tmp/flashroot/<br data-attributes="%20/">tar -xf  -C .<br data-attributes="%20/">cd /<br data-attributes="%20/">umount /tmp/flashroot<br data-attributes="%20/">ubidetach -p /dev/mtd3

For example:

 mkdir /tmp/flashroot<br data-attributes="%20/">mount -t ubifs ubi0:rootfs /tmp/flashroot/<br data-attributes="%20/">cd /tmp/flashroot/<br data-attributes="%20/">tar -xf /home/root/flash_files/my_rootfs.tar -C .<br data-attributes="%20/">cd /<br data-attributes="%20/">umount /tmp/flashroot<br data-attributes="%20/">ubidetach -p /dev/mtd3

==Flash into eMMC (Tested with iMX6-DualLite)==
'''{{Message/Information Message|message=This steps has been followed using a Linux Kernel 4.9 and a IGEP SMARC MODULE iMX6}}'''<br />Flashing into a eMMC is quite similar to flash a SD card. This tutorial is going to be focus in the i.MX chip boards. This chips specifies that the u-boot.imx file (MLO+img) has to be at the beginning without format. Knowing this we have to create the partitions in a different way, leaving 8MB before the beginning of the first partition.

<br />We begin by unmounting and clearing the partition on the eMMC (mmcblk2 in this case)

 umount /run/media/mmcblk2*<br data-attributes="%20/">parted -s /dev/mmcblk2 mklabel msdos

Now we use '''sfdisk''' to create the partitions. We are creating two partitions:

'''Partition 1''': boot

* FAT32 partition.
* Begin at the 16065 sector (leaving 8MB free before).
* Has to have the boot flag.
* It has to be <span class="guilabel">Cylinder</span> alignment. (Use <span class="guilabel">Cylinder </span>alignment to maintain compatibility with operating systems released before the year 2000, such as DOS). This setting aligns partitions to start and end on disk cylinder boundaries).
* Size of 64MB (approx).

<br />'''Partition 2:''' rootfs

* Starts after partition 1.
* Default settings
* Size of the rest of the space

<br />We transform this specifications into a sfdisk command:

 sfdisk -D -H 255 -S 63 /dev/mmcblk2 << THEEND<br data-attributes="%20/">1,8,0x0C,*<br data-attributes="%20/">9,,,-<br data-attributes="%20/">THEEND

We can check the partitions are correctly set using:

 fdisk -l /dev/mmcblk2

The result should be similar to the following:

[[File:Flash_into_eMMC.png]]



Then we finish the partitions:

 mkfs.vfat -F 32 /dev/mmcblk2p1 -n boot<br data-attributes="%20/">RFS_UUID=`cat /proc/sys/kernel/random/uuid`<br data-attributes="%20/">mkfs.ext3 -U "$RFS_UUID" "/dev/mmcblk2p2" -L rootfs
<br />Now we can create temporaly folders to work with and mount the partitions there.

 mkdir -p /tmp/mmcblk2p1<br data-attributes="%20/">mkdir -p /tmp/mmcblk2p2<br data-attributes="%20/">mount -t vfat /dev/mmcblk2p1 /tmp/mmcblk2p1<br data-attributes="%20/">mount -t ext3 /dev/mmcblk2p2 /tmp/mmcblk2p2
{| class="contenttable sortable"
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| style="border-color: #ffb521;"|
'''<u>Note</u>: If your system has automatically mounted the partitions you have to umount them again by using:'''

 umount /run/media/mmcblk2*
|}

Now we can flash the rest of the elements (by default the zImage and the dtb are place inside the rootfs boot folder).<br />First we extract the rootfs we want to flash in the temporary folder of the second partition ()

 tar -xf  -C /tmp/mmcblk2p2/<br data-attributes="%20/">For example:<br data-attributes="%20/">tar -xf<br data-attributes="%20/">/opt/firmware/isee-fsl-image-dev-imx6dl-igep0046d10-20170712121141.rootfs.<br data-attributes="%20/">tar.bz2 -C /tmp/mmcblk2p2/

At this point you can flash the u-boot.imx image using dd command and dissebling the read only protection:

 RO_PROTECTION=`cat /sys/block/mmcblk2/force_ro`<br data-attributes="%20/">echo 0 > /sys/block/mmcblk2/force_ro<br data-attributes="%20/">dd if= of=/dev/mmcblk2 bs=512 seek=2 2> /dev/null<br data-attributes="%20/">echo $RO_PROTECTION > /sys/block/mmcblk2/force_ro<br data-attributes="%20/">sync

For example:

 RO_PROTECTION=`cat /sys/block/mmcblk2/force_ro`<br data-attributes="%20/">echo 0 > /sys/block/mmcblk2/force_ro<br data-attributes="%20/">dd if=/tmp/mmcblk2p2/boot/u-boot.imx of=/dev/mmcblk2 bs=512 seek=2 2><br data-attributes="%20/">/dev/null<br data-attributes="%20/">echo $RO_PROTECTION > /sys/block/mmcblk2/force_ro<br data-attributes="%20/">sync

Finally we copy the zImage and the dtb into the first partition (boot partition)

 cp  /tmp/mmcblk2p1<br data-attributes="%20/">cp -f  /tmp/mmcblk2p1

For example:

 cp /tmp/mmcblk2p2/boot/zImage /tmp/mmcblk2p1<br data-attributes="%20/">cp -f /tmp/mmcblk2p2/boot/imx6*.dtb /tmp/mmcblk2p1

[[Category:Boot_loaders]]
[[Category:Software]]
[[Category:Software_distributions]]