mtd: omap2 fix prefetch mode read issue

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=c3341d0ceb4de1680572024f50233403c6a8b10d
Commit:     c3341d0ceb4de1680572024f50233403c6a8b10d
Parent:     f35b6eda5184e46bf2393d8970b4b9498daf7bcf
Author:     Vimal Singh <vimal.newwork at gmail.com>
AuthorDate: Thu Jan 7 12:16:26 2010 +0530
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Fri Feb 26 16:51:23 2010 +0000

    mtd: omap2 fix prefetch mode read issue
    
    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.
    
    This patch fixes the issue.
    
    Signed-off-by: Vimal Singh <vimalsingh at ti.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/nand/omap2.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 16120e2..7df303a 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -295,11 +295,14 @@ static void omap_read_buf_pref(struct mtd_info *mtd, u_char *buf, int len)
 	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);