From mboxrd@z Thu Jan 1 00:00:00 1970 From: Albert ARIBAUD Date: Mon, 06 Feb 2012 23:59:17 +0100 Subject: [U-Boot] flash post test In-Reply-To: <4F305A5A.80607@freescale.com> References: <4F2C5287.5060800@aribaud.net> <4F3052FC.4050200@aribaud.net> <4F305A5A.80607@freescale.com> Message-ID: <4F305B45.10104@aribaud.net> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de 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? > -Scott Amicalement, -- Albert.