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

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Message-ID: <20140326125502.0e8d0657@ipc1.ka-ro>
Date:	Wed, 26 Mar 2014 12:55:02 +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:
> 于 2014年03月26日 16:51, Lothar Waßmann 写道:
> > I don't see why this should not be supported on i.MX28 (i.MX23 doesn't
> > do byteswapping anyway, so this wouldn't change anything for i.MX23).
> > The partitions used by Linux need not necessarily be accessible for the
> > Boot ROM code (and vice versa).
> But the first partition used to store the u-boot is accessible for the ROM.
> 
Whether this partition is available to Linux depends on the partition table
passed in the DT.

> 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.


Lothar Waßmann
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