mtd: omap: fix subpage ecc issue with prefetch

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@ti.com>
Signed-off-by: Vimal Singh <vimal.newwork@gmail.com>
Reported-by: Bryan DE FARIA <bdefaria@adeneo-embedded.com>
Cc: stable@kernel.org [2.6.35+]
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 288423f..39f46a0 100644 (file)
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -263,11 +263,10 @@ static void omap_read_buf_pref(struct mtd_info *mtd, u_char *buf, int len)
        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);
                else
-                       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 mtd_info *mtd,
                                                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 mtd_info *mtd,
        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);
                else
-                       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;