[PATCH] mtd: mxc_nand: Set timing for v2 controllers

Hi Sascha,

On Mon, 29 Aug 2016 10:35:58 +0200
Sascha Hauer [off-list ref] wrote:

Hi Boris,

On Fri, Aug 26, 2016 at 09:46:53AM +0200, Boris Brezillon wrote:

quoted

Hi Sascha,

On Tue, 23 Aug 2016 12:34:05 +0200
Sascha Hauer [off-list ref] wrote:

AFAIR, you should apply the new mode on the NAND side
(ONFI_FEATURE_ADDR_TIMING_MODE) before applying the new config to the
controller.

See what's done here [1].

Note that on all the NANDs I tested, it seems to work even if you don't
set ONFI_FEATURE_ADDR_TIMING_MODE, but the ONFI Spec describes the
procedure as:  

Indeed, works here without notifying the NAND chip aswell. I wasn't even
aware that there is a possibility to notify the NAND chip.

quoted

1/ detect supported modes
2/ select one
3/ apply it to the NAND using set(ONFI_FEATURE_ADDR_TIMING_MODE)
4/ release the CS
5/ adjust the controller setting to match the new config

On a side note, I really think we should handle this timing selection in
the core, and only ask the NAND controller drivers to adapt the
controller settings.  

I agree that the core should do this. Do you already have any thoughts
how the API could could look like?

I already provided a simple implementation a while ago [1]. Not sure it
handles all the corner cases though.

The Nand drivers probably have to
propagate somehow which modes they support, maybe we add a onfi_modes
field to struct nand_chip. Then if onfi_modes is nonzero we call a
nand_chip->set_onfi_mode() function?

The idea was to have some way to ask the controller whether it supports
specific timings or not. I don't remember if this was part of my
initial proposal.

Note that we should pass struct real timings and not ONFI timing
mode.

Regards,

Boris

[1]https://lkml.org/lkml/2015/10/23/179