From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: Issue in oamp nand driver with 32-bit reads in prefetch mode From: Artem Bityutskiy To: Vimal Singh In-Reply-To: References: <20091223174429.GD3512@atomide.com> <5e088bd90912291238t1f2aba64na94887b2f864454d@mail.gmail.com> <5e088bd90912291347j370ab30cid7c6cfc558c2ed18@mail.gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Sun, 10 Jan 2010 10:46:35 +0200 Message-Id: <1263113195.7315.129.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Steve Sakoman , Tony Lindgren , linux-omap@vger.kernel.org, Linux MTD , linux-arm-kernel@lists.infradead.org Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2009-12-31 at 17:50 +0530, Vimal Singh wrote: > There is a bug in nand prefetch read routine, which comes into effect > only if nand device is a 16-bit device (as we have in zoom boards). > This bug is effective only with below combination of conditions: > 1. nand deivce, in use, is a 16 bit device > 2. nand driver supports 'subpage' read > 3. SW ECC is in use > > This was not seen old kernel (ex: .23), because when, in early days, > we tested this (nand prefetch read in LDP boards) there was no > 'subpage read' support. > Later when we had subpage read in (.27) kernel, we had hw ecc enabled > always in our internal tree. So, we missed this bug. > > Here is a patch to fix this issue: > > diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c > index 1bb799f..75004fe 100644 > --- a/drivers/mtd/nand/omap2.c > +++ b/drivers/mtd/nand/omap2.c > @@ -295,11 +295,14 @@ static void omap_read_buf_pref(struct > u32 *p = (u32 *)buf; > > /* take care of subpage reads */ > - for (; len % 4 != 0; ) { > - *buf++ = __raw_readb(info->nand.IO_ADDR_R); > - len--; > + if (len % 4) { > + if (info->nand.options & NAND_BUSWIDTH_16) > + omap_read_buf16(mtd, buf, len % 4); > + else > + omap_read_buf8(mtd, buf, len % 4); > + p = (u32 *) (buf + len % 4); > + len -= len % 4; > } > - p = (u32 *) buf; > > /* configure and start prefetch transfer */ > ret = gpmc_prefetch_enable(info->gpmc_cs, 0x0, len, 0x0); Pushed this patch to my l2-mtd-2.6.git/dunno. -- Best Regards, Artem Bityutskiy (Артём Битюцкий)