[E3-hacking] PBL and flash access on the E3

[Cliff Lawson]

> -----Original Message-----
> From: David Given [mailto:dg at cowlark.com]
> 
> Thanks to Cliff for the detailed explanation of how the flash metadata
> works. From that, it seems to me that the view of the flash that PBL
> sees (after bad-block remapping) is *not* the same as the view that
> Linux sees (talking directly to the chip). Which means that while I'm
> safe and won't be able to trash the metadata using PBL, I 
> *will* be able
> to trash the metadata using Linux --- and if I trash the metadata, I
> won't be able to use PBL to boot from the flash.
> 
> Could the strange issues at the end of the flash be this metadata?

Indeed,

Remember:

		{
			FSH_ALGORITHM_SMART_MEDIA,
			PBL_FLASH_DATA_BUS_WIDTH_8BIT,
			PBL_VPP_CALLBACK_NULL,
			0x00400000UL,
			0x01000000UL - (0x00400000UL +
MFS_RESERVED_BAD_BLOCKS),
			0x00000000UL,
			0x00000000UL
		}

well the 00400000 in there is the "base" address of the Nand and the
0x01000000UL - (0x00400000UL + MFS_RESERVED_BAD_BLOCKS) in there is the
length the PBL considers it has to play with as a "data" area. This is
because the end of the device is reserved for re-map sectors. That is:

	/*
	** Reserve 192KB * 4 for bad blocks (assumes 32MB part).
	*/
	#define MFS_RESERVED_BAD_BLOCKS 	((192 * 1024UL) * 4U)

Oh I forgot to mention (cos I'd forgotten!) that unlike Gamma, Delta
actually has TWO file systems in it and two MD/bad block systems. The bottom
4MB of the device has our old BSI/Gamma type FFS (Flash File System) while
the rest of the device is controlled by MFS (Mini File System) and this
includes the area where the code lives from 4MB onwards. FFS has it's MDs in
the very first sectors of the device while MFS has it's MDs in the very last
sectors of the device.

Cliff




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