[U-Boot] [PATCH v5] Corrupted NAND Flash access on KARO TX25 modules.

[Benoît Thébaudeau]

Dear Daniel, Scott,

On Thu, Aug 2, 2012 at 01:28:08 PM, Benoît Thébaudeau wrote:
> On Thu, Aug 2, 2012 at 01:17:07 PM, Daniel Gachet wrote:
> > The mxc_nand driver uses the symmetric mode to access the NAND
> > Flash,
> > but the
> > devices populated on the KARO TX25 only support ann asymmetic mode
> > (MX25: bit 8 within NAND_FLAHS_CONFIG1 register cleared).
> > 
> > This patch enables to selected the NAND Flash access mode with the
> > configuration flag CONFIG_SYS_NAND_MXC_NFC_TWO_CYCLES.
[snip]
> Why don't you simply add a factor of two to the CCM NFC divider in
> lowlevel_init.S?

To be more specific, I also have hardware based on the i.MX25 that does not use
the NAND Flash from the reference design. It works fine with the symmetric mode
as long as the NFC prescaler is set up appropriately in the MMC. I don't think
that it is possible that a NAND Flash device does not support symmetric mode. So
there should not be any need for a CONFIG_SYS_NAND_MXC_NFC_TWO_CYCLES config
option.

All you have to do is to set the appropriate value in PER8 DIV in PCDR2 (address
0x53f80020). This can easily be added as a single line to the init_clocks macro
in board/karo/tx25/lowlevel_init.S. Since the TX25 board does not set this
register, it is left at its reset value, which is 0x01010101, so the line to add
would be (dividing the NFC clock twice more):
	write32 0x53f80020, 0x01010103

This patch is interfering with a patch series that I'd like to post today or
tomorrow, so please make a quick decision about this, so that I can know if I
should take this patch into account for my series or if I should ignore it.

Best regards,
Benoît