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mtd: nand: davinci: correct 4-bit error correction 

On TI's DA830/OMAP-L137, DA850/OMAP-L138 and DM365, after setting the
4BITECC_ADD_CALC_START bit in the NAND Flash control register to 1 and
before waiting for the NAND Flash status register to be equal to 1, 2 or
3, we have to wait till the ECC HW goes to correction state.  Without this
wait, ECC correction calculations will not be proper.

This has been tested on DA830/OMAP-L137, DA850/OMAP-L138, DM355 and DM365
EVMs.

Signed-off-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Acked-by: Sneha Narnakaje <nsnehaprabha@ti.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
Sudhakar Rajashekhara 2010-07-20 15:24:01 -07:00 committed by David Woodhouse
parent 58373ff0af
commit 1c3275b656
1 changed files with 17 additions and 0 deletions
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17
drivers/mtd/nand/davinci_nand.c
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@ -311,7 +311,9 @@ static int nand_davinci_correct_4bit(struct mtd_info *mtd,
unsigned short ecc10[8];
unsigned short *ecc16;
u32 syndrome[4];
u32 ecc_state;
unsigned num_errors, corrected;
unsigned long timeo = jiffies + msecs_to_jiffies(100);
/* All bytes 0xff? It's an erased page; ignore its ECC. */
for (i = 0; i < 10; i++) {
@ -361,6 +363,21 @@ static int nand_davinci_correct_4bit(struct mtd_info *mtd,
*/
davinci_nand_writel(info, NANDFCR_OFFSET,
davinci_nand_readl(info, NANDFCR_OFFSET) | BIT(13));
/*
* ECC_STATE field reads 0x3 (Error correction complete) immediately
* after setting the 4BITECC_ADD_CALC_START bit. So if you immediately
* begin trying to poll for the state, you may fall right out of your
* loop without any of the correction calculations having taken place.
* The recommendation from the hardware team is to wait till ECC_STATE
* reads less than 4, which means ECC HW has entered correction state.
*/
do {
ecc_state = (davinci_nand_readl(info,
NANDFSR_OFFSET) >> 8) & 0x0f;
cpu_relax();
} while ((ecc_state < 4) && time_before(jiffies, timeo));
for (;;) {
u32 fsr = davinci_nand_readl(info, NANDFSR_OFFSET);