JFFS2 impact when don't have sub page access

[Gupta, Pekon]

Hi,
> 
> On Friday 02 August 2013 10:27 AM, Gupta, Pekon wrote:
> > Hello,
> >
> >> Hi,
> >>
> >> I' am using an OMAP L138 with a NAND SLC (MT29F4G08)
> >>
> >> I was making some tests with Ubifs but found some errors due to OMAP
> >> don't support sub pages access:
> >>
> > TI OMAP2-NAND supports sub-pages for SLC NAND.
> >  http://lists.infradead.org/pipermail/linux-
> mtd/attachments/20130405/a146567f/attachment.obj
> >
> > This patch was accepted in mainline linux-3.10,
> > And tested on AM335x with 2K/64 NAND.
> >
> > You can follow this patch details here..
> > http://lists.infradead.org/pipermail/linux-mtd/2013-March/046285.html
> 
> Yes, but Aníbal is talking about OMAP-L138 which is actually a DaVinci
> part and uses drivers/mtd/nand/davinci_nand.c
> 
The patch adds support for subpage-write in generic NAND driver,
So it should work directly for davinci_nand.c

> May be you can clarify whether absence of subpage support will lead to
> the kind of errors Aníbal reported?
> 
I suspect there is some mis-match in options passed while creating
UBI image for sub-pages. With subpages the LEB size (-e) passed to
 mkfs.ubifs has different calculation. It should be '(n-1) * page size'
where 'n' is number of pages in the erase-block.
This is because when using sub-pages both EraseHeader and
VolumeHeader are packed in same page.
I use some personal script to keep that handy, refer [1]
You can also refer to 
http://processors.wiki.ti.com/index.php/UBIFS_Support


> Also, the subject talks about JFFS2. There is no known affect of absence
> of subpage support on JFFS2, right?
> 
There should not be any problem in using either UBIFS or JFFS2.



[1] create_ubi_image.sh 
(this script used fixed folder name 'rootfs' as -r option)

#!/bin/sh
#---------------------------------------------------------------------- 
# Description: generic script to create UBI image for NAND devices
#		with different page sizes.
#
# Author: 	Pekon Gupta (pekon at ti.com)
# Usage:	create_ubi_image.sh <PAGE_SIZE> <SUBPAGE_SIZE> \
#						<PARTITION_SIZE>
# History:
# version 1.1	pekon
#		added calculation of LEB_SIZE while using subpages
#
#---------------------------------------------------------------------- 
#-- remove old files --
rm -v ubi.ubifs  ubi.img ubinize.cfg

#-- user inputs --
PAGE_SIZE=$1
SUBPAGE_SIZE=$2
PARTITION_SIZE=$3

if test -z $1 || test -z $2  || test -z $3
then
echo "Error: incomplete inputs"
echo "Usage: create_ubi_image.sh <PAGE_SIZE> <SUBPAGE_SIZE> <PARTITION_SIZE>"
exit
fi


#-- calculate UBI parameter --
PEB_SIZE=$(( 64 * $PAGE_SIZE ))

# LEB size =	PEB_SIZE - number_of_pages_used_for_UBI_headers * PAGE_SIZE
#		number_of_pages_used_for_UBI_header = 1 if using sub-pages
#		number_of_pages_used_for_UBI_header = 2 if not using sub-pages
if test $PAGE_SIZE -ne $SUBPAGE_SIZE
then
	LEB_SIZE=$(( $PEB_SIZE - ( 1 * $PAGE_SIZE )))
else
	LEB_SIZE=$(( $PEB_SIZE - ( 2 * $PAGE_SIZE )))
fi

LEB_COUNT=$(( $PARTITION_SIZE / $LEB_SIZE ))

echo "LOG: PAGE_SIZE	=	$PAGE_SIZE"
echo "LOG: SUBPAGE_SIZE	=	$SUBPAGE_SIZE"
echo "LOG: PEB_SIZE	=	$PEB_SIZE"
echo "LOG: LEB_SIZE	=	$LEB_SIZE"
echo "LOG: LEB_COUNT	=	$LEB_COUNT"


#-- generate ubinize.cfg --
echo "[ubifs]"                	>> ubinize.cfg 
echo "mode=ubi"               	>> ubinize.cfg 
echo "image=ubi.ubifs"        	>> ubinize.cfg 
echo "vol_id=0"               	>> ubinize.cfg 
echo "vol_size=$PARTITION_SIZE"	>> ubinize.cfg 
echo "vol_type=dynamic"       	>> ubinize.cfg 
echo "vol_name=test"         	>> ubinize.cfg 
echo "vol_flags='autoresize'" 	>> ubinize.cfg 
echo "vol_alignment=1"        	>> ubinize.cfg 

#-- generate UBI image --
mkfs.ubifs  -o ubi.ubifs  -m $PAGE_SIZE  -e $LEB_SIZE  -c $LEB_COUNT  -r rootfs
ubinize     -o ubi.img    -m $PAGE_SIZE  -p $PEB_SIZE  -s $SUBPAGE_SIZE  -O $SUBPAGE_SIZE  -v  ubinize.cfg
# ---------------------------------------------