Re: [PATCH 01/10] mtd: set the cell information for ONFI nand

[Huang Shijie <b32955@freescale.com>]

于 2013年08月13日 08:49, Brian Norris 写道:
> On Mon, Aug 12, 2013 at 07:22:38AM +0000, Gupta, Pekon wrote:
>>> The current code does not set the SLC/MLC information for onfi nand.
>>> (This makes that the kernel treats all the onfi nand as SLC nand.)
>>>
>>> This patch fills the chip->cellinfo when the onfi nand is a MLC(or TLC) nand
>>> (p->bits_per_cell>  1).
>>>
>>> The macro NAND_CI_CELLTYPE_SHIFT is added to avoid the hardcode.
>>>
>>> Signed-off-by: Huang Shijie<b32955@freescale.com>
>>> ---
>>>   drivers/mtd/nand/nand_base.c |    3 +++
>>>   include/linux/mtd/nand.h     |    1 +
>>>   2 files changed, 4 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
>>> index ff605c8..ee1aa52 100644
>>> --- a/drivers/mtd/nand/nand_base.c
>>> +++ b/drivers/mtd/nand/nand_base.c
>>> @@ -2988,6 +2988,9 @@ static int nand_flash_detect_onfi(struct mtd_info
>>> *mtd, struct nand_chip *chip,
>>>   	chip->chipsize = le32_to_cpu(p->blocks_per_lun);
>>>   	chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
>>>
>>> +	/* @bits_per_cell equals 1 means this is a SLC nand. */
>>> +	chip->cellinfo = (p->bits_per_cell - 1)<<  NAND_CI_CELLTYPE_SHIFT;
>>> +
>> [Pekon]: For future scalability, good to update only MLC related bit-fields
>> So ORing instead of assigning..
>> chip->cellinfo |= (p->bits_per_cell - 1)<<  NAND_CI_CELLTYPE_SHIFT;
> I was thinking of an alternate approach: since nand_chip.cellinfo is
> only used for checking SLC vs. MLC (and it is admittedly bad at that,
> currently), we should modify it so that is a reliable source of *only* 1
> piece of information -- the number of bits per cell. Currently, it
> contains unused (and potentially unmaintainable) information for some
> chips about number of simultaneously-programmed pages, write caching,
> internal chip numbering, etc.
I do not object to rename the cellinfo to bits_per_cell. :)
It's okay to me.

Do Artem & David (or some other people) have any opinion about this?



> byte has the correct info (you can refer to [1]) and set it with
> something like this:
>
>    chip->bits_per_cell = id_data[2]&  NAND_CI_CELLTYPE_MSK
>    chip->bits_per_cell>>= NAND_CI_CELLTYPE_SHIFT;
>    chip->bits_per_cell += 1;
>
> for chips listed by full-ID, add an appropriate flag/field; and for ONFI
> chips, just use p->bits_per_cell.
we do not need to worry about the full-id case, we can get the correct 
cell info from the id[2] for all the 4 toshiba nand.

> If you really need the other cellinfo fields in the future, we can add
> more fields to nand_chip.
>
I only need the SLC/MLC info now.

thanks
Huang Shijie
>