[PATCH RESEND] omap : nand : fix subpage ecc issue with prefetch

[PATCH RESEND] omap : nand : fix subpage ecc issue with prefetch

[Kishore Kadiyala]

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

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index da9a351..2c8040f 100644
--- 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;
-- 
1.7.4.1

Re: [stable] [PATCH RESEND] omap : nand : fix subpage ecc issue with prefetch

[Greg KH]

On Wed, May 11, 2011 at 07:54:57PM +0530, Kishore Kadiyala wrote:
> 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>
> ---
>  drivers/mtd/nand/omap2.c |   12 +++++-------
>  1 files changed, 5 insertions(+), 7 deletions(-)


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

</formletter>

Re: [stable] [PATCH RESEND] omap : nand : fix subpage ecc issue with prefetch

[Kishore Kadiyala]

On Wed, May 11, 2011 at 8:24 PM, Greg KH <greg@kroah.com> wrote:
> On Wed, May 11, 2011 at 07:54:57PM +0530, Kishore Kadiyala wrote:
>> 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>
>> ---
>>  drivers/mtd/nand/omap2.c |   12 +++++-------
>>  1 files changed, 5 insertions(+), 7 deletions(-)
>
>
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
> for how to do this properly.

Ok, will post it properly.

Regards,
Kishore
>
> </formletter>
>
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