From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Date: Mon, 6 Feb 2012 17:02:22 -0600 Subject: [U-Boot] flash post test In-Reply-To: <4F305B45.10104@aribaud.net> References: <4F2C5287.5060800@aribaud.net> <4F3052FC.4050200@aribaud.net> <4F305A5A.80607@freescale.com> <4F305B45.10104@aribaud.net> Message-ID: <4F305BFE.2020705@freescale.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 02/06/2012 04:59 PM, Albert ARIBAUD wrote: > Hi Scott, > > Le 06/02/2012 23:55, Scott Wood a ?crit : >> On 02/06/2012 04:23 PM, Albert ARIBAUD wrote: >>> Hi Vaibhav, >>> >>> Le 06/02/2012 05:57, vaibhav kothari a ?crit : >>>> 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