linux-kernel - Re: [PATCH] mtd: nand: omap: conditions with no effect

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Message-ID: <20150204114209.GA16024@opentech.at>
Date:	Wed, 4 Feb 2015 12:42:09 +0100
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Roger Quadros <rogerq@...com>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
	Tony Lindgren <tony@...mide.com>,
	Rostislav Lisovy <lisovy@...il.com>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	pekon <pekon@...-sem.com>
Subject: Re: [PATCH] mtd: nand: omap: conditions with no effect

On Wed, 04 Feb 2015, Roger Quadros wrote:

> Nicholas,
> 
> On 04/02/15 11:27, Nicholas Mc Guire wrote:
> > The if and the else branch code are identical - so the condition has no
> > effect on the effective code - this patch removes the condition and the
> > duplicated code.
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> > ---
> > 
> > The conditions in the OMAP_ECC_BCH8_CODE_HW_DETECTION_SW and
> > OMAP_ECC_BCH4_CODE_HW_DETECTION_SW case have no effect and can
> > be removed. As there are no comments it is not possible to say
> > if this is the correct solution or if this is actually a bug and
> > the two branches should be different.
> > 
> > This patch needs a review by someone who knows the details of the driver
> > 
> > Patch was only compile tested with arm-linux-gnueabi-4.7-, current
> > crosstool-ng did no not seem to compile omap2 properly.
> > Config is omap2plus_defconfig which implies CONFIG_MTD_NAND_OMAP2=y.
> > 
> > Patch is against 3.19.0-rc6 (localversion-next is -next-20150203)
> > 
> >  drivers/mtd/nand/omap2.c |   24 ++++++------------------
> >  1 file changed, 6 insertions(+), 18 deletions(-)
> 
> Your patch is correct as far as I can tell based on commits 2ef9f3ddec55, 62116e5171e0
> and 8d602cf50d3b.
> 
> The idea was to use BCH_WRAPMODE_6 for both reads and writes when we're not using the ELM
> module for error correction. i.e. BCH4_SW or BCH8_SW.
> This is mentioned in the header of omap_enable_hwecc_bch() but it is not very clear.
> So let's fix that as well with this patch.
> 
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index 63f858e..a133780 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -1048,10 +1048,9 @@ static int omap_dev_ready(struct mtd_info *mtd)
>   * @mtd: MTD device structure
>   * @mode: Read/Write mode
>   *
> - * When using BCH, sector size is hardcoded to 512 bytes.
> - * Using wrapping mode 6 both for reading and writing if ELM module not uses
> - * for error correction.
> - * On writing,
> + * When using BCH with SW correction (i.e. no ELM), sector size is set
> + * to 512 bytes and we use BCH_WRAPMODE_6 wrapping mode
> + * for both reading and writing with:
>   * eccsize0 = 0  (no additional protected byte in spare area)
>   * eccsize1 = 32 (skip 32 nibbles = 16 bytes per sector in spare area)
>   */
> 
> Then you can also add my
> 
> Acked-by: Roger Quadros <rogerq@...com>
>

thanks for the clarification !

will merge this and repost 

thx!
hofrat

 
> 
> > 
> > diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> > index 63f858e..5bcdd66 100644
> > --- a/drivers/mtd/nand/omap2.c
> > +++ b/drivers/mtd/nand/omap2.c
> > @@ -1071,15 +1071,9 @@ static void __maybe_unused omap_enable_hwecc_bch(struct mtd_info *mtd, int mode)
> >  	case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
> >  		bch_type = 0;
> >  		nsectors = 1;
> > -		if (mode == NAND_ECC_READ) {
> > -			wr_mode	  = BCH_WRAPMODE_6;
> > -			ecc_size0 = BCH_ECC_SIZE0;
> > -			ecc_size1 = BCH_ECC_SIZE1;
> > -		} else {
> > -			wr_mode   = BCH_WRAPMODE_6;
> > -			ecc_size0 = BCH_ECC_SIZE0;
> > -			ecc_size1 = BCH_ECC_SIZE1;
> > -		}
> > +		wr_mode	  = BCH_WRAPMODE_6;
> > +		ecc_size0 = BCH_ECC_SIZE0;
> > +		ecc_size1 = BCH_ECC_SIZE1;
> >  		break;
> >  	case OMAP_ECC_BCH4_CODE_HW:
> >  		bch_type = 0;
> > @@ -1097,15 +1091,9 @@ static void __maybe_unused omap_enable_hwecc_bch(struct mtd_info *mtd, int mode)
> >  	case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
> >  		bch_type = 1;
> >  		nsectors = 1;
> > -		if (mode == NAND_ECC_READ) {
> > -			wr_mode	  = BCH_WRAPMODE_6;
> > -			ecc_size0 = BCH_ECC_SIZE0;
> > -			ecc_size1 = BCH_ECC_SIZE1;
> > -		} else {
> > -			wr_mode   = BCH_WRAPMODE_6;
> > -			ecc_size0 = BCH_ECC_SIZE0;
> > -			ecc_size1 = BCH_ECC_SIZE1;
> > -		}
> > +		wr_mode	  = BCH_WRAPMODE_6;
> > +		ecc_size0 = BCH_ECC_SIZE0;
> > +		ecc_size1 = BCH_ECC_SIZE1;
> >  		break;
> >  	case OMAP_ECC_BCH8_CODE_HW:
> >  		bch_type = 1;
> > 
> 
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