Re: [PATCH] mtd: nand: gpio: make nCE GPIO optional

From: Christophe LEROY
Date: Tue May 02 2017 - 01:47:47 EST

Le 01/05/2017 à 23:46, Brian Norris a écrit :
On Fri, Feb 10, 2017 at 03:01:10PM +0100, Christophe Leroy wrote:
On some hardware, the nCE signal is wired to the ChipSelect associated
to bus address of the NAND, so it is automatically driven during the
memory access and it is not managed by a GPIO.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>

Not really a problem with this patch exactly, but FYI you're only making
this optional for the non-DT case. For device tree, this is kinda hard
to do, since the current binding suggests we retrieve the GPIOs based on
index position, not by name. So if you leave one off...I guess we well
just be off-by-1 on the indeces until we hit a non-optional one...which
I guess is "CLE".

If we wanted this to work for DT, we'd need to extend this driver (and
binding doc) to support requesting GPIOs by name.

It works for me with devicetree.

I have the following definition in my DT:

nand@1,0 {
compatible = "gpio-control-nand";
reg = <1 0x0 0x01>;
#address-cells = <1>;
#size-cells = <1>;
gpios = <&qe_pio_c 24 1 // RDY
0 // nCE
&qe_pio_c 26 1 // ALE
&qe_pio_c 25 1 // CLE
0>; // nwp