[FE training-materials-updates] sysdev-flash-filesystems: Use trimffs to write the JFFS2 image

[Gregory Clement]

Repository : git://git.free-electrons.com/training-materials.git

On branch  : master
Link       : http://git.free-electrons.com/training-materials/commit/?id=683047def58f9446c6f30e4cd9f2d65e356983fe

>---------------------------------------------------------------

commit 683047def58f9446c6f30e4cd9f2d65e356983fe
Author: Gregory CLEMENT <gregory.clement at free-electrons.com>
Date:   Mon Feb 2 16:53:20 2015 +0100

    sysdev-flash-filesystems: Use trimffs to write the JFFS2 image
    
    Signed-off-by: Gregory CLEMENT <gregory.clement at free-electrons.com>


>---------------------------------------------------------------

683047def58f9446c6f30e4cd9f2d65e356983fe
 labs/sysdev-flash-filesystems/sysdev-flash-filesystems.tex | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/labs/sysdev-flash-filesystems/sysdev-flash-filesystems.tex b/labs/sysdev-flash-filesystems/sysdev-flash-filesystems.tex
index bf9e98c..dda9752 100644
--- a/labs/sysdev-flash-filesystems/sysdev-flash-filesystems.tex
+++ b/labs/sysdev-flash-filesystems/sysdev-flash-filesystems.tex
@@ -86,6 +86,13 @@ of the root filesystem the correct location.
 Using the \code{tftp} command, download and flash the JFFS2 image of
 the data filesystem at the correction location.
 
+Use the \code{trimffs} version of the command \code{nand write} for the
+JFFS2 image. The command \code{nand write.trimffs} skips the blank
+sectors instead of writing them. It is needed because the algorithm
+used by the hardware ECC for the SAMA5D3 SoC generates a checksum with
+bytes different of 0xFF if the page is blank, whereas Linux expects to
+have the OOB full of 0xFF if the associated page is blank too.
+
 Don't forget that you can write U-Boot scripts to automate these
 procedures. This is very handy to avoid mistakes when typing commands!