Re: [PATCH] mtd: gpmi: Remove "We support only one NAND chip" from bindings doc

[Stefan Roese <sr@denx.de>]

On 30.11.2014 16:42, Huang Shijie wrote:
> On Sat, Nov 29, 2014 at 10:53:26PM -0800, Brian Norris wrote:
>> On Sat, Nov 29, 2014 at 10:40:50AM +0800, Huang Shijie wrote:
>>> On Fri, Nov 28, 2014 at 08:01:41AM +0100, Stefan Roese wrote:
>>>> On 28.11.2014 02:48, Huang Shijie wrote:
>>>>> On Thu, Nov 27, 2014 at 03:18:49PM +0100, Stefan Roese wrote:
>>>>>> This sentence "We support only one NAND chip now" is not true any more.
>>>>>> Multiple chips are supported. So lets remove this sentence to not
>>>>>
>>>>> The gpmi can only supports one chip. Of course, there are maybe two dies
>>>>> in this single chip.
>>>>
>>>> Now I'm a bit confused. The i.MX6 supports 4 chips select signals. And isn't
>>>> "two dies in this single chip" not practically the same as connecting 2 (or
>>>> more) chips (same device) to multiple chip selects of the SoC? Where is the
>>>> difference here?
>>> The "one chip" here is means the "one package" (TSOP or BGA ....).
>>
>> Then why is this even in the DT binding doc? Isn't that a board-level
>> constraint (and not a chip property) which should be obvious to the
>> user? If so, then should we just drop the language? Or at a minimum,
>> make it more specific so it doesn't confuse readers.
> 
> yes. It is okay to send a patch to make it more clear.
> 
>>
>>> (In logic, "two dies in this single chip" is same as connecting 2 chips
>>> to the gpmi.)
>>
>> ...which means that logically, you can connect more than one chip to the
>> GPMI, right?
> The gpmi can only connect with one physical chip now, but there maybe
> two DIEs in this chip.

I really fail to see why you make this distinction between two chips on a die
and two external chips. For the SoC this should really look identical, right?

Please explain again, why exactly only two chips on one die are supported.

BTW: We have a custom i.MX6DL based board with 2 NAND chips connected. And
Linux seems to support both chips just fine. Here the boot log:

[    1.085812] nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xdc
[    1.092218] nand: Micron MT29F4G08ABADAH4
[    1.096245] nand: 512MiB, SLC, page size: 2048, OOB size: 64
[    1.102171] nand: 2 chips detected
[    1.106156] gpmi-nand 112000.gpmi-nand: enable the asynchronous EDO mode 5
[    1.113094] Scanning device for bad blocks

Comments welcome...

Thanks,
Stefan