[032/165] mtd: omap: fix subpage ecc issue with prefetch

From: Greg KH
Date: Wed Jun 01 2011 - 05:00:20 EST

2.6.39-stable review patch. If anyone has any objections, please let us know.

Content-Length: 2505
Lines: 68

From: Kishore Kadiyala <kishore.kadiyala@xxxxxx>

commit c5d8c0cae4af7d78823d32fcd1c458ee1a1b5489 upstream.

When reading/writing a subpage (When HW ECC is not available/enabled)
for number of bytes not aligned to 4, the mis-aligned bytes are handled
first (by cpu copy method) before enabling the Prefetch engine to/from
'p'(start of buffer 'buf'). Then it reads/writes rest of the bytes with
the help of Prefetch engine, if available, or again using cpu copy method.
Currently, reading/writing of rest of bytes, is not done correctly since
its trying to read/write again to/from begining of buffer 'buf',
overwriting the mis-aligned bytes.

Read & write using prefetch engine got broken in commit '2c01946c'.
We never hit a scenario of not getting 'gpmc_prefetch_enable' call
success. So, problem did not get caught up.

Signed-off-by: Kishore Kadiyala <kishore.kadiyala@xxxxxx>
Signed-off-by: Vimal Singh <vimal.newwork@xxxxxxxxx>
Reported-by: Bryan DE FARIA <bdefaria@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>
Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

drivers/mtd/nand/omap2.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)

--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -263,11 +263,10 @@ static void omap_read_buf_pref(struct mt
if (ret) {
/* PFPW engine is busy, use cpu copy method */
if (info->nand.options & NAND_BUSWIDTH_16)
- omap_read_buf16(mtd, buf, len);
+ omap_read_buf16(mtd, (u_char *)p, len);
- omap_read_buf8(mtd, buf, len);
+ omap_read_buf8(mtd, (u_char *)p, len);
} else {
- p = (u32 *) buf;
do {
r_count = gpmc_read_status(GPMC_PREFETCH_FIFO_CNT);
r_count = r_count >> 2;
@@ -293,7 +292,7 @@ static void omap_write_buf_pref(struct m
struct omap_nand_info, mtd);
uint32_t w_count = 0;
int i = 0, ret = 0;
- u16 *p;
+ u16 *p = (u16 *)buf;
unsigned long tim, limit;

/* take care of subpage writes */
@@ -309,11 +308,10 @@ static void omap_write_buf_pref(struct m
if (ret) {
/* PFPW engine is busy, use cpu copy method */
if (info->nand.options & NAND_BUSWIDTH_16)
- omap_write_buf16(mtd, buf, len);
+ omap_write_buf16(mtd, (u_char *)p, len);
- omap_write_buf8(mtd, buf, len);
+ omap_write_buf8(mtd, (u_char *)p, len);
} else {
- p = (u16 *) buf;
while (len) {
w_count = gpmc_read_status(GPMC_PREFETCH_FIFO_CNT);
w_count = w_count >> 1;

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