linux-kernel - Re: [RFC PATCH v2 0/4] mtd: nand: add per partition ECC config

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Message-ID: <CAGVrzcZei92K9Jeue-Yvcev7n08YEEqfRbN2xgqLpW7epMzFVA@mail.gmail.com>
Date:	Wed, 12 Feb 2014 11:49:55 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Boris BREZILLON <b.brezillon.dev@...il.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Gupta Pekon <pekon@...com>
Subject: Re: [RFC PATCH v2 0/4] mtd: nand: add per partition ECC config

Hi Boris,

2014-02-11 13:46 GMT-08:00 Boris BREZILLON <b.brezillon.dev@...il.com>:
> Hello,
>
> This patch series is a proposal to add per partition ECC config.
>
> It defines a new partition type called nand_part which stores a pointer to
> a nand_ecc_ctrl struct.
> This specific nand_ecc_ctrl struct is used in place of the base NAND chip
> nand_ecc_ctrl struct when accessing NAND chip from nand_part MTD device.
>
> If the partition does not define any ECC config, the NAND chip ECC config
> is used instead.

Although the idea does look nice on the paper, I wonder if it is
really useful to have that much complexity in the kernel. Most likely
what is happening is that your bootloader partition has a specific ECC
scheme due to the CPU bootrom or whatever early bootagent is running
on the system. When that is the case, this can be solved in user-space
by preparing full pages (main+spare) along with their specific ECC
requirements and use the MTD_FILE_MODE_RAW option on your specific MTD
partition.

You do not describe what is the end goal of this patchset, which might
help figuring out the potential other platforms requirements etc...

>
> This patch series also provides an helper function to parse DT defined NAND
> partitions (ofnandpart_parse).
>
> If you want to test it you'll have to replace calls to
> mtd_device_parse_register with ofnandpart_parse within your NAND controller
> driver and implement a driver specific parser function that will provide
> the ECC config (see ofnandpart_data struct).
>
> The 4th patch of this series is here as an example on how to move from MTD
> partitions to NAND partitions.
>
> Best Regards,
>
> Boris
>
> Changes since v1:
> - almost everything :-)
>
> Boris BREZILLON (4):
>   mtd: nand: take nand_ecc_ctrl initialization out of nand_scan_tail
>   mtd: nand: add support for NAND partitions
>   mtd: nand: add DT NAND partition parser
>   mtd: nand: add NAND partition support to the sunxi driver
>
>  drivers/mtd/nand/Kconfig      |    4 +
>  drivers/mtd/nand/Makefile     |    2 +
>  drivers/mtd/nand/nand_base.c  |  763 ++++++++++++++++++++++++++++++++---------
>  drivers/mtd/nand/ofnandpart.c |  104 ++++++
>  drivers/mtd/nand/sunxi_nand.c |   69 +++-
>  include/linux/mtd/nand.h      |   54 +++
>  6 files changed, 835 insertions(+), 161 deletions(-)
>  create mode 100644 drivers/mtd/nand/ofnandpart.c
>
> --
> 1.7.9.5
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

-- 
Florian
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