From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from va3ehsobe005.messaging.microsoft.com ([216.32.180.31]
 helo=VA3EHSOBE005.bigfish.com)
 by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux))
 id 1RiJqm-0004jg-11
 for linux-mtd@lists.infradead.org; Wed, 04 Jan 2012 05:57:24 +0000
Message-ID: <4F03EA83.9030503@freescale.com>
Date: Wed, 4 Jan 2012 13:58:27 +0800
From: Huang Shijie <b32955@freescale.com>
MIME-Version: 1.0
To: Marek Vasut <marek.vasut@gmail.com>
Subject: Re: GPMI-NAND: Wrong ECC size in driver
References: <201201040148.32847.marek.vasut@gmail.com>
In-Reply-To: <201201040148.32847.marek.vasut@gmail.com>
Content-Type: text/plain; charset="ISO-8859-1"; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Scott Wood <scottwood@freescale.com>, linux-mtd@lists.infradead.org
List-Id: Linux MTD discussion mailing list <linux-mtd.lists.infradead.org>
List-Unsubscribe: <http://lists.infradead.org/mailman/options/linux-mtd>,
 <mailto:linux-mtd-request@lists.infradead.org?subject=unsubscribe>
List-Archive: <http://lists.infradead.org/pipermail/linux-mtd/>
List-Post: <mailto:linux-mtd@lists.infradead.org>
List-Help: <mailto:linux-mtd-request@lists.infradead.org?subject=help>
List-Subscribe: <http://lists.infradead.org/mailman/listinfo/linux-mtd>,
 <mailto:linux-mtd-request@lists.infradead.org?subject=subscribe>

Hi Marek:
> Hi,
>
> the gpmi-nand.c driver apparently has misconfigured ecc.size field:
>
> drivers/mtd/nand/gpmi-nand/gpmi-nand.c:
> ---------->8 ----------
> 1493         chip->ecc.mode          = NAND_ECC_HW;
> 1494         chip->ecc.size          = 1;
> 1495         chip->ecc.layout        =&gpmi_hw_ecclayout;
> ---------- 8<  ----------
>
> This boils down to misconfigured mtd->subpage_sft in:
>
> drivers/mtd/nand/nand_base.c:
> ---------->8 ----------
> 3434         /* Allow subpage writes up to ecc.steps. Not possible for MLC flash
> */
> 3435         if (!(chip->options&  NAND_NO_SUBPAGE_WRITE)&&
> 3436             !(chip->cellinfo&  NAND_CI_CELLTYPE_MSK)) {
> 3437                 switch (chip->ecc.steps) {
> 3438                 case 2:
> 3439                         mtd->subpage_sft = 1;
> 3440                         break;
> 3441                 case 4:
> 3442                 case 8:
> 3443                 case 16:
> 3444                         mtd->subpage_sft = 2;
> 3445                         break;
> 3446                 }
> 3447         }
> 3448         chip->subpagesize = mtd->writesize>>  mtd->subpage_sft;
> ---------- 8<  ----------
>
> The mtd->subpage_sft is accidentally 0 by default. Therefore, the subpage size
> is mtd->writesize>>  0. Therefore the subpage size reported to UBI formating
> tools is the size of whole page, which works. Now, if I correct the problem by
> setting ecc.size properly to 512 bytes, I get into trouble with UBI:
>
> 1) UBI formating tools are reported the driver CAN DO subpage writes
> 2) UBI formating tools are reported the subpage size is 512 bytes
>
The gpmi driver does not support the subpage read/write.
I will be happy if the driver works only by setting the 
NAND_NO_SUBPAGE_WRITE, without setting the ecc.size.

Best Regards
Huang Shijie
> and this happens even though the NAND_NO_SUBPAGE_WRITE option is set by the
> driver. This is because:
>
> drivers/mtd/nand/nand_base.c:
> ---------->8 ----------
> 3072         /* Get chip options, preserve non chip based options */
> 3073         chip->options&= ~NAND_CHIPOPTIONS_MSK;
> 3074         chip->options |= type->options&  NAND_CHIPOPTIONS_MSK;
> ---------- 8<  ----------
>
> which effectively masks that bit away. So, how are we going to fix it?
>
> Cheers!
>
> Marek
>