[U-Boot] [PATCHv3] mtd: sf: Add CONFIG_SPI_N25Q256A_RESET for software-reset

[Marek Vasut <marex@denx.de>]

On Sunday, May 10, 2015 at 02:24:01 PM, Jagan Teki wrote:
> On 10 May 2015 at 16:19, Pavel Machek <pavel@denx.de> wrote:
> > On Sun 2015-05-10 11:15:41, Pavel Machek wrote:
> > Add reset for N25Q256A SPI NOR, as U-Boot SPL 2013-socfpga (only
> > version working on that board) sets 4-byte addressing mode.
> > 
> > Signed-off-by: Pavel Machek <pavel@denx.de>

So, I took one more look into the datasheet [1]. With this chip, which
is 128Mbit (16MByte), you don't even use 4-byte addressing so you don't
care about it at all.

But you actually do care about it if your hardware is broken and you use
the N25Q256A [2] part. If the problem really is just between the U-Boot
SPL and U-Boot (which I doubt btw), you can probably augment U-Boot such
that it reads FSR (Flag Status Register, see page 27, table 17, bit 0).
This bit tells you whether the part is in 3-byte or 4-byte mode and you
can read this register in either mode.

Same applies to N25Q512A [3], FSR bit 0 indicates the mode.

[1] https://www.micron.com/~/media/documents/products/data-sheet/nor-
flash/serial-nor/n25q/n25q_128mb_1_8v_65nm.pdf
[2] https://www.micron.com/~/media/documents/products/data-sheet/nor-
flash/serial-nor/n25q/n25q_256mb_3v_65nm.pdf
[3] https://www.micron.com/~/media/documents/products/data-sheet/nor-
flash/serial-nor/n25q/n25q_512mb_1ce_3v_65nm.pdf

Best regards,
Marek Vasut