Erase Block size

Erase Block size

[Sugathan, Rupesh]

Hi,

I have a scenario where I need to deploy the same jffs2 image on two
flash memory parts, one with a 128KB sector size and the other with
256KB sector size.

I read from http://www.linux-mtd.infradead.org/doc/jffs2.html that
building the jffs2 image with smaller 'erase block size' should be
harmless even in the flash with 256KB sector size, although there might
be some warning messages at mount time. However, the warning messages
are not desired since this is a production image. 

Can anyone tell me if there is any utility that can be used to alter the
erase block size on-the-fly? Or I would greatly appreciate if anyone has
some other solution to this problem.

Thanks
--
Rupesh

Re: Erase Block size

[Ricard Wanderlof]

On Wed, 10 Sep 2008, Sugathan, Rupesh wrote:

> I have a scenario where I need to deploy the same jffs2 image on two
> flash memory parts, one with a 128KB sector size and the other with
> 256KB sector size.
>
> I read from http://www.linux-mtd.infradead.org/doc/jffs2.html that
> building the jffs2 image with smaller 'erase block size' should be
> harmless even in the flash with 256KB sector size, although there might
> be some warning messages at mount time. However, the warning messages
> are not desired since this is a production image.
>
> Can anyone tell me if there is any utility that can be used to alter the
> erase block size on-the-fly? Or I would greatly appreciate if anyone has
> some other solution to this problem.

I'm not aware of any such utility.

You could always patch the kernel in your production image to avoid the 
warnings.

We had a similar situation where we wanted to run the same image on 
several NAND flash types with different block sizes. In the end we gave 
up, because the issues with managing multiple block sizes, especially 
regarding live firmware upgrades, made it not worth while. Instead, we 
simply said that changing the flash so that the block/sector size changes 
is considered a hardware change and must be handled accordingly (separate 
firmware, etc).

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30
    "With Free Software you are employing the best programmers on the planet"

Re: Erase Block size

[michael]

Hi,

Ricard Wanderlof wrote:
> On Wed, 10 Sep 2008, Sugathan, Rupesh wrote:
>
>   
>> I have a scenario where I need to deploy the same jffs2 image on two
>> flash memory parts, one with a 128KB sector size and the other with
>> 256KB sector size.
>>
>> I read from http://www.linux-mtd.infradead.org/doc/jffs2.html that
>> building the jffs2 image with smaller 'erase block size' should be
>> harmless even in the flash with 256KB sector size, although there might
>> be some warning messages at mount time. However, the warning messages
>> are not desired since this is a production image.
>>
>> Can anyone tell me if there is any utility that can be used to alter the
>> erase block size on-the-fly? Or I would greatly appreciate if anyone has
>> some other solution to this problem.
>>     
You can use linux to flash image :). Erase the flash, mount it and 
install file.

Regards Michael

RE: Erase Block size

[Ricard Wanderlof]

On Thu, 11 Sep 2008, Sugathan, Rupesh wrote:

> Thanks for sharing your solution. Can you please comment if the below
> understanding correct.
> Cause of the warning messages are 'empty space' within the erase block.
> One of the problems of these empty spaces is a small waste of space in
> Flash. Is there any other problem in having these empty space on a
> write-able partition?

No, I don't think so.

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30
    "With Free Software you are employing the best programmers on the planet"