ARM: at91: atmel_nand: add code to check the ONFI parameter ECC requirement

1. if CONFIG_SYS_NAND_ONFI_DETECTION is defined, driver will check NAND flash's
   ecc minimum requirement in ONFI parameter.

  a) if CONFIG_PMECC_CAP, CONFIG_PMECC_SECTOR_SIZE are defined. then use it.
     Driver will display a WARNING if the values are different from ONFI
     parameters.

  b) if CONFIG_PMECC_CAP, CONFIG_PMECC_SECTOR_SIZE are not defined, then use
      the value from ONFI parameters.
      * If ONFI ECC parameters are in ONFI extended parameter page, since we
        are not support it, so assume the minimum ecc requirement is 2 bits
        in 512 bytes.
      * For non-ONFI support nand flash, also assume the minimum ecc
        requirement is 2 bits in 512 bytes.

2. if CONFIG_SYS_NAND_ONFI_DETECTION is not defined, just use CONFIG_PMECC_CAP
   and CONFIG_PMECC_SECTOR_SIZE.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>

drivers/mtd/nand/atmel_nand.c

@@ -665,6 +665,99 @@ static void atmel_pmecc_core_init(struct mtd_info *mtd)
 	pmecc_writel(host->pmecc, ctrl, PMECC_CTRL_ENABLE);
 }
 
+#ifdef CONFIG_SYS_NAND_ONFI_DETECTION
+/*
+ * get_onfi_ecc_param - Get ECC requirement from ONFI parameters
+ * @ecc_bits: store the ONFI ECC correct bits capbility
+ * @sector_size: in how many bytes that ONFI require to correct @ecc_bits
+ *
+ * Returns -1 if ONFI parameters is not supported. In this case @ecc_bits,
+ * @sector_size are initialize to 0.
+ * Return 0 if success to get the ECC requirement.
+ */
+static int get_onfi_ecc_param(struct nand_chip *chip,
+		int *ecc_bits, int *sector_size)
+{
+	*ecc_bits = *sector_size = 0;
+
+	if (chip->onfi_params.ecc_bits == 0xff)
+		/* TODO: the sector_size and ecc_bits need to be find in
+		 * extended ecc parameter, currently we don't support it.
+		 */
+		return -1;
+
+	*ecc_bits = chip->onfi_params.ecc_bits;
+
+	/* The default sector size (ecc codeword size) is 512 */
+	*sector_size = 512;
+
+	return 0;
+}
+
+/*
+ * pmecc_choose_ecc - Get ecc requirement from ONFI parameters. If
+ *                    pmecc_corr_cap or pmecc_sector_size is 0, then set it as
+ *                    ONFI ECC parameters.
+ * @host: point to an atmel_nand_host structure.
+ *        if host->pmecc_corr_cap is 0 then set it as the ONFI ecc_bits.
+ *        if host->pmecc_sector_size is 0 then set it as the ONFI sector_size.
+ * @chip: point to an nand_chip structure.
+ * @cap: store the ONFI ECC correct bits capbility
+ * @sector_size: in how many bytes that ONFI require to correct @ecc_bits
+ *
+ * Return 0 if success. otherwise return the error code.
+ */
+static int pmecc_choose_ecc(struct atmel_nand_host *host,
+		struct nand_chip *chip,
+		int *cap, int *sector_size)
+{
+	/* Get ECC requirement from ONFI parameters */
+	*cap = *sector_size = 0;
+	if (chip->onfi_version) {
+		if (!get_onfi_ecc_param(chip, cap, sector_size)) {
+			MTDDEBUG(MTD_DEBUG_LEVEL1, "ONFI params, minimum required ECC: %d bits in %d bytes\n",
+				*cap, *sector_size);
+		} else {
+			dev_info(host->dev, "NAND chip ECC reqirement is in Extended ONFI parameter, we don't support yet.\n");
+		}
+	} else {
+		dev_info(host->dev, "NAND chip is not ONFI compliant, assume ecc_bits is 2 in 512 bytes");
+	}
+	if (*cap == 0 && *sector_size == 0) {
+		/* Non-ONFI compliant or use extended ONFI parameters */
+		*cap = 2;
+		*sector_size = 512;
+	}
+
+	/* If head file doesn't specify then use the one in ONFI parameters */
+	if (host->pmecc_corr_cap == 0) {
+		/* use the most fitable ecc bits (the near bigger one ) */
+		if (*cap <= 2)
+			host->pmecc_corr_cap = 2;
+		else if (*cap <= 4)
+			host->pmecc_corr_cap = 4;
+		else if (*cap <= 8)
+			host->pmecc_corr_cap = 8;
+		else if (*cap <= 12)
+			host->pmecc_corr_cap = 12;
+		else if (*cap <= 24)
+			host->pmecc_corr_cap = 24;
+		else
+			return -EINVAL;
+	}
+	if (host->pmecc_sector_size == 0) {
+		/* use the most fitable sector size (the near smaller one ) */
+		if (*sector_size >= 1024)
+			host->pmecc_sector_size = 1024;
+		else if (*sector_size >= 512)
+			host->pmecc_sector_size = 512;
+		else
+			return -EINVAL;
+	}
+	return 0;
+}
+#endif
+
 static int atmel_pmecc_nand_init_params(struct nand_chip *nand,
 		struct mtd_info *mtd)
 {
@@ -678,8 +771,41 @@ static int atmel_pmecc_nand_init_params(struct nand_chip *nand,
 	nand->ecc.correct = NULL;
 	nand->ecc.hwctl = NULL;
 
-	cap = host->pmecc_corr_cap = CONFIG_PMECC_CAP;
-	sector_size = host->pmecc_sector_size = CONFIG_PMECC_SECTOR_SIZE;
+#ifdef CONFIG_SYS_NAND_ONFI_DETECTION
+	host->pmecc_corr_cap = host->pmecc_sector_size = 0;
+
+#ifdef CONFIG_PMECC_CAP
+	host->pmecc_corr_cap = CONFIG_PMECC_CAP;
+#endif
+#ifdef CONFIG_PMECC_SECTOR_SIZE
+	host->pmecc_sector_size = CONFIG_PMECC_SECTOR_SIZE;
+#endif
+	/* Get ECC requirement of ONFI parameters. And if CONFIG_PMECC_CAP or
+	 * CONFIG_PMECC_SECTOR_SIZE not defined, then use ecc_bits, sector_size
+	 * from ONFI.
+	 */
+	if (pmecc_choose_ecc(host, nand, &cap, &sector_size)) {
+		dev_err(host->dev, "The NAND flash's ECC requirement(ecc_bits: %d, sector_size: %d) are not support!",
+				cap, sector_size);
+		return -EINVAL;
+	}
+
+	if (cap > host->pmecc_corr_cap)
+		dev_info(host->dev, "WARNING: Using different ecc correct bits(%d bit) from Nand ONFI ECC reqirement (%d bit).\n",
+				host->pmecc_corr_cap, cap);
+	if (sector_size < host->pmecc_sector_size)
+		dev_info(host->dev, "WARNING: Using different ecc correct sector size (%d bytes) from Nand ONFI ECC reqirement (%d bytes).\n",
+				host->pmecc_sector_size, sector_size);
+#else	/* CONFIG_SYS_NAND_ONFI_DETECTION */
+	host->pmecc_corr_cap = CONFIG_PMECC_CAP;
+	host->pmecc_sector_size = CONFIG_PMECC_SECTOR_SIZE;
+#endif
+
+	cap = host->pmecc_corr_cap;
+	sector_size = host->pmecc_sector_size;
+
+	/* TODO: need check whether cap & sector_size is validate */
+
 	if (host->pmecc_sector_size == 512)
 		host->pmecc_index_table_offset = ATMEL_PMECC_INDEX_OFFSET_512;
 	else