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Message-ID: <20160418094444.152042ee@bbrezillon>
Date: Mon, 18 Apr 2016 09:44:44 +0200
From: Boris Brezillon <boris.brezillon@...e-electrons.com>
To: Peter Pan <peterpansjtu@...il.com>
Cc: Brian Norris <computersforpeace@...il.com>,
David Woodhouse <dwmw2@...radead.org>,
linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
karlzhang@...ron.com, beanhuo@...ron.com,
Jiancheng Xue <xuejiancheng@...wei.com>,
Peter Pan <peterpandong@...ron.com>
Subject: Re: [PATCH 02/11] mtd: nand_bbt: introduce BBT related data
structure
Hi Peter,
On Mon, 18 Apr 2016 14:22:09 +0800
Peter Pan <peterpansjtu@...il.com> wrote:
> Hi Boris,
>
> On Fri, Mar 25, 2016 at 4:35 PM, Boris Brezillon
> <boris.brezillon@...e-electrons.com> wrote:
> > Hi Peter,
> >
> > On Mon, 14 Mar 2016 02:47:55 +0000
> > Peter Pan <peterpansjtu@...il.com> wrote:
> >
> >> From: Brian Norris <computersforpeace@...il.com>
> >>
> >> 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@...il.com>
> >> [Peter: 1. correct comment style
> >> 2. introduce struct nand_bbt_ops and nand_chip_layout_info]
> >> Signed-off-by: Peter Pan <peterpandong@...ron.com>
> >> ---
> >> 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.
> 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.
Best Regards,
Boris
[1]https://github.com/bbrezillon/linux-sunxi/commits/nand/generic
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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