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Date: Thu, 06 Oct 2011 14:29:08 +0200
From: angelo <angelo70@gmail.com>
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Subject: cfi_cmdset_0002.c SST39VF3201B issue
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Dear all,

like me some other users had issues with this chip and jffs2.

 From time to time users asks why they get errors trying to use jffs2 
with this chip.

This chip, from the datasheet, allows to erase 4KB "sectors" or 64KB 
"blocks", replying to cfi queries with a "setcor" erase size and a 
"block" erase size.

I can be wrong of course, but this is what i figured out:


1) fixup decision

Someone of you decided to fix up this SST39VF3201 in this way:

static void fixup_old_sst_eraseregion(struct mtd_info *mtd)
{
     struct map_info *map = mtd->priv;
     struct cfi_private *cfi = map->fldrv_priv;

     /*
      * These flashes report two seperate eraseblock regions based on the
      * sector_erase-size and block_erase-size, although they both 
operate on the
      * same memory. This is not allowed according to CFI, so we just 
pick the
      * sector_erase-size.
      */
     cfi->cfiq->NumEraseRegions = 1;
}

Of course, in this way, deciding 0x1000 (sector-size) is the one to use, 
jffs2 cannot be used safely, since
minimal data block is 4Kb + some hdr bytes. Wasn't better fixup to 
"block" size (64K) ?


2) after fixup decision, when jffs2 asks to erase a block to 
cfi_cmdset_0002.c, cfi driver seems to erase wrongly a 64K block.
This is what happen in detail:
    jffs erase.c, to erase a block does:  mtd->erase(), with a len  
mtd->erasesize (4KB).
    mtd->erase() is calls cfi_amdstd_erase_varsize ...
      finally, do_erase_oneblock is called, where:

cfi_send_gen_cmd(0xAA, cfi->addr_unlock1, chip->start, map, cfi, 
cfi->device_type, NULL);
cfi_send_gen_cmd(0x55, cfi->addr_unlock2, chip->start, map, cfi, 
cfi->device_type, NULL);
cfi_send_gen_cmd(0x80, cfi->addr_unlock1, chip->start, map, cfi, 
cfi->device_type, NULL);
cfi_send_gen_cmd(0xAA, cfi->addr_unlock1, chip->start, map, cfi, 
cfi->device_type, NULL);
cfi_send_gen_cmd(0x55, cfi->addr_unlock2, chip->start, map, cfi, 
cfi->device_type, NULL);
map_write(map, CMD(0x30), adr);

but this chip uses 0x30 cmd to erase a 64 KB block, and 0x50 to erase a 
sector.

Please let me know if i am in the right direction, so i can think about 
a patch that allows
jffs2 to be used with native hw 64KB block erasesize.

Regards
Angelo Dureghello