mtd: at91: atmel_nand: for PMECC, add code to check the ONFI parameter ECC requirement.

This patch will check NAND flash's ecc minimum requirement in ONFI parameter.

1. if pmecc-cap, pmecc-sector-size is set in dts. then use it. Driver will
   print out a WARNING if the values are different from ONFI parameters.
2. if pmecc-cap, pmecc-sector-size is not set in dts, 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.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

1 files changed, 87 insertions, 3 deletions

diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
index f186a371e437..ffcbcca2fd2d 100644
--- a/drivers/mtd/nand/atmel_nand.c
+++ b/drivers/mtd/nand/atmel_nand.c
@@ -910,6 +910,84 @@ static void atmel_pmecc_core_init(struct mtd_info *mtd)
         pmecc_writel(host->ecc, CTRL, PMECC_CTRL_ENABLE);
 }
 
+/*
+ * Get ECC requirement in ONFI parameters, returns -1 if ONFI
+ * parameters is not supported.
+ * 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;
+}
+
+/*
+ * Get ecc requirement from ONFI parameters ecc requirement.
+ * If pmecc-cap, pmecc-sector-size in DTS are not specified, this function
+ * will set them according to ONFI ecc requirement. Otherwise, use the
+ * value in DTS file.
+ * return 0 if success. otherwise return error code.
+ */
+static int pmecc_choose_ecc(struct atmel_nand_host *host,
+                int *cap, int *sector_size)
+{
+        /* Get ECC requirement from ONFI parameters */
+        *cap = *sector_size = 0;
+        if (host->nand_chip.onfi_version) {
+                if (!get_onfi_ecc_param(&host->nand_chip, cap, sector_size))
+                        dev_info(host->dev, "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) {
+                *cap = 2;
+                *sector_size = 512;
+        }
+
+        /* If dts 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;
+}
+
 static int __init atmel_pmecc_nand_init_params(struct platform_device *pdev,
                                          struct atmel_nand_host *host)
 {
@@ -918,9 +996,15 @@ static int __init atmel_pmecc_nand_init_params(struct platform_device *pdev,
         struct resource *regs, *regs_pmerr, *regs_rom;
         int cap, sector_size, err_no;
 
-        if (host->pmecc_corr_cap == 0 || host->pmecc_sector_size == 0)
-                /* TODO: Should use ONFI ecc parameters. */
-                return -EINVAL;
+        err_no = pmecc_choose_ecc(host, &cap, &sector_size);
+        if (err_no) {
+                dev_err(host->dev, "The NAND flash's ECC requirement are not support!");
+                return err_no;
+        }
+
+        if (cap != host->pmecc_corr_cap ||
+                        sector_size != host->pmecc_sector_size)
+                dev_info(host->dev, "WARNING: Be Caution! Using different PMECC parameters from Nand ONFI ECC reqirement.\n");
 
         cap = host->pmecc_corr_cap;
         sector_size = host->pmecc_sector_size;