imx6 NAND chip selects

[Hugo Villeneuve <hugo@hugovil.com>]

Hi,
I am trying to connect a NAND flash device (Micron MT29F8G08) to a 
Wandboard Dual.

Here is the pin mapping:

i.MX6             NAND flash
----------------------------
NANDF_CS0    -->  CE#
NANDF_RB0    -->  R/B#
NANDF_WP_B   -->  WP#
NANDF_CLE    -->  CLE
NANDF_ALE    -->  ALE
NANDF_WE     -->  WE#
NANDF_RE     -->  RE#
NANDF_D[0-7] -->  I/O[0-7]

This NAND flash has a single chip-select.

I'm testing it using Linux kernel 3.15.0-rc3.

In the wandboard device tree file, I have added all the above gpmi pins 
as GPMI pins.

I am still booting from the SD card, so at this point I am only trying 
to detect the NAND device. Unfortunately, when the kernel boots, the 
GPMI driver fails to register (error -19).

If I monitor the NANDF_CS0 line, I can see that it is pulsed low, but I 
am not seing any activity on the NANDF_WE line.

However, If I monitor the NANDF_CS1 line, I can see that it is pulsed 
low, and during the time it is low the NANDF_WE line is also going low.

I then made sure to reconfigure the unused pins NANDF_CS[1-3] as GPIOs 
(ALT5 function) in my device tree file. I have confirmed with kernel 
debug traces that the iomux register for NANDF_CS1 have the value 0x05, 
which means ALT5 function (GPIO). But I am still seeing the same 
behavior as before on the oscilloscope.

So how can I configure the GPMI driver to only use NANDF_CS0 and not 
NANDF_CS1?

And is it normal that NANDF_CS1 is still used by the GPMI driver when 
configured as GPIO?

Hugo.