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From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: linux-mtd@lists.infradead.org, Enrico Jorns <ejo@pengutronix.de>,
	Artem Bityutskiy <artem.bityutskiy@linux.intel.com>,
	Dinh Nguyen <dinguyen@kernel.org>,
	Marek Vasut <marek.vasut@gmail.com>,
	Graham Moore <grmoore@opensource.altera.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Chuanxiao Dong <chuanxiao.dong@intel.com>,
	Jassi Brar <jaswinder.singh@linaro.org>,
	devicetree@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Brian Norris <computersforpeace@gmail.com>,
	Richard Weinberger <richard@nod.at>,
	Cyrille Pitchen <cyrille.pitchen@atmel.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v3 14/37] mtd: nand: denali: support "nand-ecc-strength" DT property
Date: Fri, 31 Mar 2017 14:06:32 +0900	[thread overview]
Message-ID: <CAK7LNARUKwMHd79ALDx_SDY9XKcHPY96xTAOMQx6XarFgwb-AA@mail.gmail.com> (raw)
In-Reply-To: <20170330160238.59e5a2c1@bbrezillon>

Hi Boris,


2017-03-30 23:02 GMT+09:00 Boris Brezillon <boris.brezillon@free-electrons.com>:
> On Thu, 30 Mar 2017 15:46:00 +0900
> Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
>
>> Historically, this driver tried to choose as big ECC strength as
>> possible, but it would be reasonable to allow DT to set a particular
>> ECC strength with "nand-ecc-strength" property.  This is useful
>> when a particular ECC setting is hard-coded by firmware (or hard-
>> wired by boot ROM).
>>
>> If no ECC strength is specified in DT, "nand-ecc-maximize" is implied
>> since this was the original behavior.
>
> You said there is currently no DT users,

Right.  No DT users ever in upstream.


> so how about changing the
> "fallback to ECC maximization" behavior for DT users, and instead of
> maximizing the ECC strength take the NAND requirements into account
> (chip->ecc_strength_ds).

This is difficult to judge in some cases.

As I said before, 4/512 and 8/1024 are not equivalent.

If chip's requirement  chip->ecc_step_ds matches
to the ecc->size supported by the controller,
this is easy.


If a chip requests 1024B, then the controller can only support 512B chunk
(or vice versa), it is difficult to simply compare
ecc strength.

Is it a bad thing if we use too strong ECC strength?

The disadvantage I see is we will have less OOB-free bytes,
but this will not be fatal, I guess.




-- 
Best Regards
Masahiro Yamada

  reply	other threads:[~2017-03-31  5:06 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-30  6:45 [PATCH v3 00/37] mtd: nand: denali: 2nd round of Denali NAND IP patch bomb Masahiro Yamada
2017-03-30  6:45 ` Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 01/37] mtd: nand: relax ecc.read_page() return value for uncorrectable ECC Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 02/37] mtd: nand: denali: allow to override mtd->name from label DT property Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 03/37] mtd: nand: denali: remove meaningless pipeline read-ahead operation Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 04/37] mtd: nand: denali: fix bitflips calculation in handle_ecc() Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 05/37] mtd: nand: denali: fix erased page checking Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 06/37] mtd: nand: denali: support HW_ECC_FIXUP capability Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 07/37] mtd: nand: denali_dt: enable HW_ECC_FIXUP for Altera SOCFPGA variant Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 08/37] mtd: nand: denali: support 64bit capable DMA engine Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 09/37] mtd: nand: denali_dt: remove dma-mask DT property Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 10/37] mtd: nand: denali_dt: use pdev instead of ofdev for platform_device Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 11/37] mtd: nand: denali: allow to override revision number Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 12/37] mtd: nand: denali: support 1024 byte ECC step size Masahiro Yamada
2017-03-30  6:45   ` Masahiro Yamada
2017-04-01  8:43   ` Masahiro Yamada
2017-04-01  8:43     ` Masahiro Yamada
2017-03-30  6:45 ` [PATCH v3 13/37] mtd: nand: denali: avoid hard-coding ecc.strength and ecc.bytes Masahiro Yamada
2017-03-31  9:09   ` Boris Brezillon
2017-03-30  6:46 ` [PATCH v3 14/37] mtd: nand: denali: support "nand-ecc-strength" DT property Masahiro Yamada
2017-03-30  6:46   ` Masahiro Yamada
2017-03-30 14:02   ` Boris Brezillon
2017-03-30 14:02     ` Boris Brezillon
2017-03-31  5:06     ` Masahiro Yamada [this message]
2017-03-31  9:46       ` Boris Brezillon
2017-04-03  3:16         ` Masahiro Yamada
2017-04-03  3:16           ` Masahiro Yamada
2017-04-09 16:33           ` Boris Brezillon
2017-04-09 16:33             ` Boris Brezillon
2017-04-11  6:19             ` Masahiro Yamada
2017-04-11  6:19               ` Masahiro Yamada
2017-04-11  7:56               ` Boris Brezillon
2017-04-11  7:56                 ` Boris Brezillon
2017-04-14  7:57                 ` Masahiro Yamada
2017-04-14  8:19                   ` Boris Brezillon
2017-04-14  8:19                     ` Boris Brezillon
2017-04-22 15:00                     ` Masahiro Yamada
2017-04-22 15:00                       ` Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 15/37] mtd: nand: denali: remove Toshiba and Hynix specific fixup code Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 16/37] mtd: nand: denali_dt: add compatible strings for UniPhier SoC variants Masahiro Yamada
2017-04-03 15:46   ` Rob Herring
2017-04-03 15:46     ` Rob Herring
2017-03-30  6:46 ` [PATCH v3 17/37] mtd: nand: denali: set NAND_ECC_CUSTOM_PAGE_ACCESS Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 18/37] mtd: nand: denali: do not propagate NAND_STATUS_FAIL to waitfunc() Masahiro Yamada
2017-03-30 15:17   ` Boris Brezillon
2017-03-30  6:46 ` [PATCH v3 19/37] mtd: nand: denali: use BIT() and GENMASK() for register macros Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 20/37] mtd: nand: denali: remove unneeded find_valid_banks() Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 21/37] mtd: nand: denali: handle timing parameters by setup_data_interface() Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 22/37] mtd: nand: denali: rework interrupt handling Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 23/37] mtd: nand: denali: fix NAND_CMD_STATUS handling Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 24/37] mtd: nand: denali: fix NAND_CMD_PARAM handling Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 25/37] mtd: nand: denali: switch over to cmd_ctrl instead of cmdfunc Masahiro Yamada
2017-03-30 15:55   ` Boris Brezillon
2017-03-30  6:46 ` [PATCH v3 26/37] mtd: nand: denali: fix bank reset function Masahiro Yamada
2017-03-30 16:16   ` Boris Brezillon
2017-04-03  7:05     ` Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 27/37] mtd: nand: denali: use interrupt instead of polling for bank reset Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 28/37] mtd: nand: denali: propagate page to helpers via function argument Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 29/37] mtd: nand: denali: merge struct nand_buf into struct denali_nand_info Masahiro Yamada
2017-03-30  6:46 ` [PATCH v3 30/37] mtd: nand: denali: use flag instead of register macro for direction Masahiro Yamada
2017-03-30 16:38 ` [PATCH v3 00/37] mtd: nand: denali: 2nd round of Denali NAND IP patch bomb Boris Brezillon
2017-03-30 16:38   ` Boris Brezillon
2017-03-31  4:05   ` Masahiro Yamada
2017-03-31  8:27     ` Boris Brezillon

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