[RESEND PATCH 1/3] mtd: nand: Pass the CS line to ->setup_data_interface()

On Tue, 21 Feb 2017 13:02:48 +0100
Marc Gonzalez [off-list ref] wrote:

On 21/02/2017 12:06, Boris Brezillon wrote:

quoted

Marc Gonzalez wrote:
  

quoted

On 20/02/2017 22:12, Boris Brezillon wrote:
 

quoted

Some NAND controllers can assign different NAND timings to different
CS lines. Pass the CS line information to ->setup_data_interface() so
that the NAND controller driver knows which CS line is concerned by
the setup_data_interface() request.    

I'm confused, because I thought I was already doing that.
On my platform, I have different timings for each chip.
(thus, for each CS, right?)

In chip->select_chip, I program the appropriate timings
which the controller will be using.

What am I missing?  

Maybe you don't have multi-dies chips, which is the case I'm fixing
here. If you have 2 separate chips, the existing hook should work just
fine.  

Right. You asked me to add an explicit:

	res = of_property_count_u32_elems(np, "reg");
	if (res < 0)
		return res;

	if (res != 1)
		return -ENOTSUPP; /* Multi-CS chips are not supported */

I was under the impression that multi-die chips are seen as a single
larger "composite" chip. And I had assumed that different dies would
not only require identical timings, but would also be identical in
all other aspects. This it incorrect?

This is correct, except some chips (that's true at least for ONFI
compatible ones) allow dynamic configuration of timings, and each die
can be configured in a different timing mode.

That's what's happening when you reset dies. They will automatically
enter timing mode 0 (the slowest mode), and you have to explicitly set
them back to timing mode X (the fastest supported mode). While doing
that, you'll have some of your dies configured in timing 0, while
others have already been switched to timing mode X, and that's the main
reason for having per-die timing configuration.