On 02/06/2012 04:59 PM, Albert ARIBAUD wrote:
Hi Scott,
Le 06/02/2012 23:55, Scott Wood a écrit :
On 02/06/2012 04:23 PM, Albert ARIBAUD wrote:
Hi Vaibhav,
Le 06/02/2012 05:57, vaibhav kothari a écrit :
hi albert
Yes,actually there is already support of flash test in POST of latest uboot.They are testing flash on every power on so am I for my board.But i don't want to disturb sectors in which uboot code relies. Can you help me here?
I am no NAND specialist, but I do hope NAND POST tests are pure read tests and thus are not affected by poweroffs (and can actually test any part of NAND).
NAND has a property called "read disturb", where excessively reading a sector without writing to it can eventually cause data loss. U-Boot is already read once per boot, but reading it a second time could halve the expected lifetime. Data managed by something like ubi is be scrubbed in a way that avoids this, but U-Boot itself is not usually managed in this way (boot hardware/rom does not understand ubi).
I *did* say I am not a NAND expert. :)
Thanks Scott. But then, isn't NAND testing a kind of catch-22, where by actually tesing if NAND works it one ends up weakening it either through read disturb, or simply through writes?
It's fine for occasional manual testing, or routine testing of an area that gets properly scrubbed.
-Scott