From patchwork Tue Nov 3 10:31:10 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: mtd-nand: davinci: Correct 4-bit error correction Date: Tue, 03 Nov 2009 00:31:10 -0000 From: "Rajashekhara, Sudhakar" X-Patchwork-Id: 37503 Message-Id: <1257244270-2433-1-git-send-email-sudhakar.raj@ti.com> To: linux-mtd@lists.infradead.org Cc: akpm@linux-foundation.org, Sudhakar Rajashekhara , nsnehaprabha@ti.com, davinci-linux-open-source@linux.davincidsp.com 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 Acked-by: Sneha Narnakaje --- drivers/mtd/nand/davinci_nand.c | 16 ++++++++++++++++ 1 files changed, 16 insertions(+), 0 deletions(-) diff --git a/drivers/mtd/nand/davinci_nand.c b/drivers/mtd/nand/davinci_nand.c index fe3eba8..8a32999 100644 --- a/drivers/mtd/nand/davinci_nand.c +++ b/drivers/mtd/nand/davinci_nand.c @@ -310,6 +310,7 @@ 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; /* All bytes 0xff? It's an erased page; ignore its ECC. */ @@ -360,6 +361,21 @@ compare: */ 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); + for (;;) { u32 fsr = davinci_nand_readl(info, NANDFSR_OFFSET);