Re: [PATCH 02/11] mtd: nand_bbt: introduce BBT related data structure

[Peter Pan]

Hi Boris,

On Mon, Apr 18, 2016 at 3:44 PM, Boris Brezillon
<boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
> Hi Peter,
>
> On Mon, 18 Apr 2016 14:22:09 +0800
> Peter Pan <peterpansjtu@xxxxxxxxx> wrote:
>
>> Hi  Boris,
>>
>> On Fri, Mar 25, 2016 at 4:35 PM, Boris Brezillon
>> <boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
>> > Hi Peter,
>> >
>> > On Mon, 14 Mar 2016 02:47:55 +0000
>> > Peter Pan <peterpansjtu@xxxxxxxxx> wrote:
>> >
>> >> From: Brian Norris <computersforpeace@xxxxxxxxx>
>> >>
>> >> Currently nand_bbt.c is tied with struct nand_chip, and it makes other
>> >> NAND family chips hard to use nand_bbt.c. Maybe it's the reason why
>> >> onenand has own bbt(onenand_bbt.c).
>> >>
>> >> Separate struct nand_chip from BBT code can make current BBT shareable.
>> >> We create struct nand_bbt to take place of nand_chip in nand_bbt.c
>> >>
>> >> Below is mtd folder structure we want:
>> >>       drivers/mtd/nand/<all-nand-core-code>
>> >>       drivers/mtd/nand/raw/<raw-nand-controller-drivers>
>> >>       drivers/mtd/nand/spi/<spi-nand-code>
>> >>       drivers/mtd/nand/onenand/<onenand-code>
>> >>       drivers/mtd/nand/chips/<manufacturer-spcific-code>
>> >>
>> >> Of course, nand_bbt.c should be part of <all-nand-core-code>.
>> >>
>> >> We put every chip layout related information BBT needed into struct
>> >> nand_chip_layout_info.
>> >>       @numchips:      number of physical chips, required for NAND_BBT_PERCHIP
>> >>       @chipsize:      the size of one chip for multichip arrays
>> >>       @chip_shift:    number of address bits in one chip
>> >>       @bbt_erase_shift:       number of address bits in a bbt entry
>> >>       @page_shift:    number of address bits in a page
>> >>
>> >> We defined a struct nand_bbt_ops for BBT ops. Struct
>> >>       @is_bad_bbm:    check if a block is factory bad block
>> >>       @erase: erase block bypassing resvered checks
>> >>
>> >> Struct nand_bbt includes all BBT information:
>> >>       @mtd:   pointer to MTD device structure
>> >>       @bbt_options:   bad block specific options. All options used
>> >>                       here must come from nand_bbt.h.
>> >>       @bbt_ops:       struct nand_bbt_ops pointer.
>> >>       @info:          struct nand_chip_layout_info pointer.
>> >>       @bbt_td:        bad block table descriptor for flash lookup.
>> >>       @bbt_md:        bad block table mirror descriptor
>> >>       @bbt:           bad block table pointer
>> >>
>> >> Signed-off-by: Brian Norris <computersforpeace@xxxxxxxxx>
>> >> [Peter: 1. correct comment style
>> >>       2. introduce struct nand_bbt_ops and nand_chip_layout_info]
>> >> Signed-off-by: Peter Pan <peterpandong@xxxxxxxxxx>
>> >> ---
>> >>  include/linux/mtd/nand_bbt.h | 67 ++++++++++++++++++++++++++++++++++++++++++++
>> >>  1 file changed, 67 insertions(+)
>> >>
>> >> diff --git a/include/linux/mtd/nand_bbt.h b/include/linux/mtd/nand_bbt.h
>> >> index 5a65230..cfb22c8 100644
>> >> --- a/include/linux/mtd/nand_bbt.h
>> >> +++ b/include/linux/mtd/nand_bbt.h
>> >> @@ -18,6 +18,8 @@
>> >>  #ifndef __LINUX_MTD_NAND_BBT_H
>> >>  #define __LINUX_MTD_NAND_BBT_H
>> >>
>> >> +struct mtd_info;
>> >> +
>> >>  /* The maximum number of NAND chips in an array */
>> >>  #define NAND_MAX_CHIPS               8
>> >>
>> >> @@ -115,4 +117,69 @@ struct nand_bbt_descr {
>> >>  /* The maximum number of blocks to scan for a bbt */
>> >>  #define NAND_BBT_SCAN_MAXBLOCKS      4
>> >>
>> >> +struct nand_bbt;
>> >> +
>> >> +/**
>> >> + * struct nand_bbt_ops - bad block table operations
>> >> + * @is_bad_bbm:      check if a block is factory bad block
>> >> + * @erase:   erase block bypassing resvered checks
>> >> + */
>> >> +struct nand_bbt_ops {
>> >> +     /*
>> >> +      * This is important to abstract out of nand_bbt.c and provide
>> >> +      * separately in nand_base.c and spi-nand-base.c -- it's sort of
>> >> +      * duplicated in nand_block_bad() (nand_base) and
>> >> +      * scan_block_fast() (nand_bbt) right now
>> >> +      *
>> >> +      * Note that this also means nand_chip.badblock_pattern should
>> >> +      * be removed from nand_bbt.c
>> >> +      */
>> >> +     int (*is_bad_bbm)(struct mtd_info *mtd, loff_t ofs);
>> >> +
>> >> +     /* Erase a block, bypassing reserved checks */
>> >> +     int (*erase)(struct mtd_info *mtd, loff_t ofs);
>> >> +};
>> >> +
>> >> +/**
>> >> + * struct nand_chip_layout_info - strucure contains all chip layout
>> >> + * information that BBT needed.
>> >> + * @numchips:        number of physical chips, required for NAND_BBT_PERCHIP
>> >> + * @chipsize:        the size of one chip for multichip arrays
>> >> + * @chip_shift:      number of address bits in one chip
>> >> + * @bbt_erase_shift: number of address bits in a bbt entry
>> >> + * @page_shift:      number of address bits in a page
>> >> + */
>> >> +struct nand_chip_layout_info {
>> >
>> > I know I'm the one who suggested this name, but NAND datasheet seems to
>> > call it "memory organization", so maybe we should rename this struct
>> > nand_memory_organization.
>> >
>> >> +     int numchips;
>> >
>> > I would rename it numdies, or ndies. numchips implies you're having
>> > several chips, which is not the case.
>>
>> In struct nand_chip and nand_base.c, numchips stands for the number of
>> physical nand chips not number of dies(LUNs), am I right?
>
> I don't know what was the initial meaning for ->numchips, but last time
> we discussed that with Brian, he seemed to agree that this should now
> encode the number of dies in a physical chip, and each physical chip
> should have its own nand_chip instance. That's why I suggested to
> rename this field nand_chip_layout_info.

OK. This is clear. Thanks.

>
>> So it's true, it
>> should still be numchips in nand_bbt.c?  I just came out this question when
>> making v4. :)
>
> BTW, I have something for you [1]. I started to move things around to
> allow spinand and onenand layers to lie under drivers/mtd/nand/, and I
> wonder if we shouldn't do this move before reworking the nand_bbt code
> to make it generic.
> Note that this rework is not finished yet, but it gives a rough idea of
> what I'd like to see.

I saw you also rework BBT in your git tree, which is a bit duplicate
with my BBT patch,
so should I continue my BBT patch by join part of your BBT rework code
or continue
your git tree ?

Thanks,
Peter Pan