Re: UBI - exclude bootloader blocks from wear levelling

[Lauren Del Giudice <lauren@wyplay.com>]

Yes, this is my use case. So I would be in trouble if bootloader (a
first stage loader) does no longer reside at 0.
Thanks, anyway.

Lauren.

Darwin Rambo wrote:
> I think Lauren must have been referring to a bootloader that lives outside the kernel and file system context. For example, a small, standalone bootloader downloaded from a serial port to it's own partition, would not be known to the kernel, as it is used to launch the kernel or later stage bootloaders. In this case it runs standalone and can't sit on UBI or be launched by a linux app. If this small bootloader was only a block or two in size, and since it is typically burned once for production and then becomes read-only for each bootup after that, wear levelling is not required or possible.
> 
> Flash data retention periods are usually specified in years, and flash write/erases are in cycles. MLC and SLC flashes typically mention 10 year lifetimes in their data sheets, and the program/erase cycles are typically 100K-1M for SLC, and 10K-100K for MLC. As such I don't see an issue wrt boot loader integrity on factory burning or years of subsequent bootups. 
> 
> Hope this helps a bit. 
> 
> Darwin
> 
> -----Original Message-----
> From: linux-mtd-bounces@lists.infradead.org [mailto:linux-mtd-bounces@lists.infradead.org] On Behalf Of Wolfgang Denk
> Sent: Tuesday, December 22, 2009 10:33 PM
> To: Lauren Del Giudice
> Cc: linux-mtd@lists.infradead.org
> Subject: Re: UBI - exclude bootloader blocks from wear levelling
> 
> Dear Lauren Del Giudice,
> 
> In message <4B2FA658.6010407@wyplay.com> you wrote:
>> I'm new to UBI... I understood that static wear levelling is applied
>> accross the whole device (a NAND device in my case); If so, how can
>> I exclude blocks reserved for the bootloader from wear levelling?
> 
> Why would you want to do that? You should be happy that UBI also
> applies wear levelling to the bootloader storage, as this prevents
> your device from bricking when read errors develop there. Keep in mind
> that NAND blocks will develop read errors even if you only read them
> (i. e. there is not only a limit on the number of erase cycles of such
> a device, but also on the number of read cycles).
> 
> It is a great benefit if your boot loader gets loaded from a UBI
> partition instead of raw NAND.
> 
> Best regards,
> 
> Wolfgang Denk
>