linux-kernel - Re: [PATCHv2 1/1] mtd: gpmi: make blockmark swapping optional

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Date:	Thu, 27 Mar 2014 13:21:09 +0100
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Huang Shijie <b32955@...escale.com>
Cc:	Fabio Estevam <fabio.estevam@...escale.com>,
	Mark Rutland <mark.rutland@....com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Pawel Moll <pawel.moll@....com>, Arnd Bergmann <arnd@...db.de>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
	<linux-mtd@...ts.infradead.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Rob Landley <rob@...dley.net>,
	Kumar Gala <galak@...eaurora.org>,
	Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Shawn Guo <shawn.guo@...escale.com>
Subject: Re: [PATCHv2 1/1] mtd: gpmi: make blockmark swapping optional

Hi,

Huang Shijie wrote:
> > > Please see "Figure 12-13" in the 12.12.1.12:
> > >    "In order to preserve the BI (bad block information), flash updater 
> > > or gang programmer
> > > applications need to swap Bad Block Information (BI) data to byte 0 of 
> > > metadata area for
> > > every page before programming NAND Flash. ROM when loading firmware, 
> > > copies back
> > > the value at metadata[0] to BI offset in page data. The following figure 
> > > shows how the
> > > factory bad block marker is preserved."
> > > 
> > The inspection of the BB markers is only a fallback for the case that
> > there is no DBBT. From the same chapter that you quoted above:
> > | ROM uses DBBT to skip any bad block that falls within firmware data
> > | on NAND Flash device.
> > | If the address of DBBT Search Area in FCB is 0, ROM will rely on
> > | factory marked bad block markers to find out if a block is good or bad.
> > 
> > Thus, even the boot ROM of i.MX28 can well live without blockmark
> > swapping.
> 
> Assume that there is a NAND block "A",  and the A consist of 256 pages.
> the uboot is burned to the "A", can occupy 6 pages:
> 
>   -----------------------------------------------------------------------------
>  | page 0 |  page 1 | page 2 | page 3 | page 4 | page 5 | ... | ... | page 255 |
>   -----------------------------------------------------------------------------
>  
>   \-------------------------------------- ------------------------------------/
>                                          V  
>                                         "A"					 
> 
> The DBBT is used to track if "A" is bad or not.
> Assume we know that "A" is a good block, ROM then need to read out the uboot.
> When the ROM needs to read out the 6 pages one by one. And each time the ROM read
> the page, it should do the swapping for this page.
> 
> In this case, the ROM will do the swapping six times.
> 
> Please read the sector again, you will see the "every page" in it:
> --------------------------------------------------------------------
>    "In order to preserve the BI (bad block information), flash updater 
> or gang programmer applications need to swap Bad Block Information (BI) data to byte 0 of 
> metadata area for every page before programming NAND Flash. ROM when loading firmware, 
> copies back
> --------------------------------------------------------------------
>
I can assure you that the >100.000 i.MX28 based modules, that we sold
up to now boot from NAND just fine without any block mark swapping in
the U-Boot pages.


Lothar Waßmann
-- 
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