OneNAND: read-while-load (known problem)

[Kyungmin Park]

Hi Adrian, 

> Do you think there could be a problem with onenand_check_bufferram also?

No, onenand_check_bufferram & onenand_update_bufferram is right.

In DDP, actually there's 4 bufferrams

Chip 0: 0, 1
Chip 1: 0, 1

In case read from chip 0 to chip 1, first send command at chip 0: 0 or 1, next we also send command at chip 1: 1 or 0, repectively,
in that case. second command will be failed. 
To fix this problem, we add some code to check chip boundary condition in DDP. but it's overhead since there's no usage in current MTD

I think it is best way we send the read buffer with block aligned.

Thank you,
Kyungmin Park


------- Original Message -------
Sender : Adrian Hunter<hunter.programmer at gmail.com> 
Date   : Jan 08, 2007 16:47
Title  : Re: OneNAND: read-while-load (known problem)

On 1/8/07, Kyungmin Park <kyungmin.park at samsung.com> wrote:
> Hi,
>
> FYI: read-while-load known problem in DDP.
>
> Of course it's rare case in MTD. and please don't program like this in upper layer.
>
> If you are using OneNAND DDP (Dual Densidy Package) and you want to read data between chip boundary. you maybe failed to read.
>
> For example, 2Gbit OneNAND DDP has following address
>
> Chip 0: 0x0000 0000 ~ 0x0800 0000 - 1
> Chip 1: 0x0800 0000 ~ 0x1000 0000 - 1
>
> If you want to read from 0x07ff f800 to 0x8000 0800 (4KB). it will be failed since each chip has its own bufferram
> So it don't support read-while-loading between each chip.
>
> [Chip 0] onenand_update_bufferram: 1 addr 0x7ffe000, valid = 1
> [Chip 0] onenand_update_bufferram: 0 addr 0x7ffe800, valid = 1
> [Chip 0] onenand_update_bufferram: 1 addr 0x7fff000, valid = 1
> [Chip 0] onenand_update_bufferram: 0 addr 0x7fff800, valid = 1
>   -> Send next page read, but next page is in chip 1
> [Chip 1] onenand_update_bufferram: 1 addr 0x8000000, valid = 1 => Actually it's invalid
> [Chip 1] onenand_update_bufferram: 0 addr 0x8000800, valid = 1
> [Chip 1] onenand_update_bufferram: 1 addr 0x8001000, valid = 1
>
> Thank you,
> Kyungmin Park

I think I see what you mean.  It occurs to me that maybe
onenand_check_bufferram has the same problem i.e. a different chip is
selected to the one that we want to read from.  Do you think there
could be a problem with onenand_check_bufferram also?