linux-kernel - Re: [PATCH 3/4] Enable ecc-mode selection in the driver

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Message-ID: <20130116132422.GI17242@lunn.ch>
Date:	Wed, 16 Jan 2013 14:24:22 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Stefan Peter <s.peter@....ch>
Cc:	Andrew Lunn <andrew@...n.ch>, devicetree-discuss@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org, grant.likely@...retlab.ca,
	rob.herring@...xeda.com, rob@...dley.net, linux@....linux.org.uk,
	jason@...edaemon.net, dwmw2@...radead.org, jm@...tin.co.uk,
	arnd@...db.de, sebastian.hesselbarth@...glemail.com,
	iwamatsu@...auri.org, artem.bityutskiy@...ux.intel.com,
	wfp5p@...ginia.edu, gregkh@...uxfoundation.org,
	broonie@...nsource.wolfsonmicro.com, mchehab@...hat.com,
	nico@...aro.org
Subject: Re: [PATCH 3/4] Enable ecc-mode selection in the driver

On Wed, Jan 16, 2013 at 12:43:57PM +0100, Stefan Peter wrote:
> Hi Andrew
> 
> on 15.01.2013 13:51, Andrew Lunn wrote:
> > On Tue, Jan 15, 2013 at 01:13:12PM +0100, Stefan Peter wrote:
> >> In order to be able to use the ecc-mode, add the bch module to the default
> >> settings for the kirwood boards and enable the activation in orin-nand.c
> >>
> >> Signed-off-by: Stefan Peter <s.peter@....ch>
> >> ---
> >> diff --git a/arch/arm/configs/kirkwood_defconfig b/arch/arm/configs/kirkwood_defconfig
> >> index 93f3794..4a9d3f7 100644
> >> --- a/arch/arm/configs/kirkwood_defconfig
> >> +++ b/arch/arm/configs/kirkwood_defconfig
> >> @@ -84,6 +84,7 @@ CONFIG_MTD_CFI_STAA=y
> >>  CONFIG_MTD_PHYSMAP=y
> >>  CONFIG_MTD_M25P80=y
> >>  CONFIG_MTD_NAND=y
> >> +CONFIG_MTD_NAND_ECC_BCH=y
> >>  CONFIG_MTD_NAND_ORION=y
> >>  CONFIG_BLK_DEV_LOOP=y
> >>  # CONFIG_SCSI_PROC_FS is not set
> >> diff --git a/drivers/mtd/nand/orion_nand.c b/drivers/mtd/nand/orion_nand.c
> >> index cd72b92..1a35257 100644
> >> --- a/drivers/mtd/nand/orion_nand.c
> >> +++ b/drivers/mtd/nand/orion_nand.c
> >> @@ -14,6 +14,7 @@
> >>  #include <linux/module.h>
> >>  #include <linux/platform_device.h>
> >>  #include <linux/of.h>
> >> +#include <linux/of_mtd.h>
> >>  #include <linux/mtd/mtd.h>
> >>  #include <linux/mtd/nand.h>
> >>  #include <linux/mtd/partitions.h>
> >> @@ -130,6 +131,7 @@ static int __init orion_nand_probe(struct platform_device *pdev)
> >>  		if (!of_property_read_u32(pdev->dev.of_node,
> >>  						"chip-delay", &val))
> >>  			board->chip_delay = (u8)val;
> >> +		board->ecc_mode = of_get_nand_ecc_mode(pdev->dev.of_node);
> > 
> >>  	} else
> >>  		board = pdev->dev.platform_data;
> >>  
> >> @@ -140,7 +142,8 @@ static int __init orion_nand_probe(struct platform_device *pdev)
> >>  	nc->IO_ADDR_R = nc->IO_ADDR_W = io_base;
> >>  	nc->cmd_ctrl = orion_nand_cmd_ctrl;
> >>  	nc->read_buf = orion_nand_read_buf;
> >> -	nc->ecc.mode = NAND_ECC_SOFT;
> >> +	nc->ecc.mode = board->ecc_mode == NAND_ECC_SOFT_BCH ?
> >> +		NAND_ECC_SOFT_BCH : NAND_ECC_SOFT;
> > 
> > Hi Stefan
> > 
> > What about a user that wants one of the other valid values?
> > NAND_ECC_OOB_FIRST, NAND_ECC_HW_SYNDROME, etc.
> 
> As far as I understand, NAND_ECC_NONE, NAND_ECC_SOFT and
> NAND_ECC_SOFT_BCH are the only ECC modes that do not require
> corresponding hardware support which is missing in the marvell
> 88F6180/88F619x/88F628x. From my point of view, NAND_ECC_NONE does not
> make sense, too, because MLC NAND Flash requires ECC to be usable.
> 
> > 
> > Would:
> > 
> > 	if (IS_ERR(board->ecc_mode)) {
> > 		nc->ecc.mode = NAND_ECC_SOFT;
> > 		dev_info(&pdev->dev, "Defaulting to NAND_ECC_SOFT");
> > 	} else
> > 		nc->ecc.mode = board->ecc_mode
> > 
> > be better?
> 
> I feel safer by limiting the modes to what I could test.

Hi Stefan

O.K, but i still think a warning message would be useful when
board->ecc_mode is an error code.

		Andrew
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