Historically, this driver tried to choose as big ECC strength as
possible, but it would be reasonable to allow DT to set a particular
ECC strength with "nand-ecc-strength" property.  This is useful
when a particular ECC setting is hard-coded by firmware (or hard-
wired by boot ROM).

If no ECC strength is specified in DT, "nand-ecc-maximize" is implied
since this was the original behavior.

Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com>
Acked-by: Rob Herring <r...@kernel.org>
---

Changes in v3: None
Changes in v2:
  - Add available values in the binding document

 Documentation/devicetree/bindings/mtd/denali-nand.txt |  6 ++++++
 drivers/mtd/nand/denali.c                             | 18 ++++++++++++++++--
 drivers/mtd/nand/denali_pci.c                         |  1 +
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/mtd/denali-nand.txt 
b/Documentation/devicetree/bindings/mtd/denali-nand.txt
index 25313c7..647618e 100644
--- a/Documentation/devicetree/bindings/mtd/denali-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/denali-nand.txt
@@ -11,6 +11,12 @@ Optional properties:
   - nand-ecc-step-size: must be 512 or 1024.  If not specified, default to:
       512   for "altr,socfpga-denali-nand"
     see nand.txt for details.
+  - nand-ecc-strength: see nand.txt for details.  Available values are:
+      8, 15      for "altr,socfpga-denali-nand"
+  - nand-ecc-maximize: see nand.txt for details
+
+Note:
+Either nand-ecc-strength or nand-ecc-maximize should be specified.
 
 The device tree may optionally contain sub-nodes describing partitions of the
 address space. See partition.txt for more detail.
diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index ce87b95..2f796e3 100644
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -1641,9 +1641,23 @@ int denali_init(struct denali_nand_info *denali)
                goto failed_req_irq;
        }
 
-       ret = denali_set_max_ecc_strength(denali);
-       if (ret)
+       if (!chip->ecc.strength && !(chip->ecc.options & NAND_ECC_MAXIMIZE)) {
+               dev_info(denali->dev,
+                        "No ECC strength strategy is specified. Maximizing ECC 
strength\n");
+               chip->ecc.options |= NAND_ECC_MAXIMIZE;
+       }
+
+       if (chip->ecc.options & NAND_ECC_MAXIMIZE) {
+               ret = denali_set_max_ecc_strength(denali);
+               if (ret)
+                       goto failed_req_irq;
+       } else if (!(denali->ecc_strength_avail & BIT(chip->ecc.strength))) {
+               dev_err(denali->dev,
+                       "ECC strength %d is not supported on this 
controller.\n",
+                       chip->ecc.strength);
+               ret = -EINVAL;
                goto failed_req_irq;
+       }
 
        chip->ecc.bytes = denali_calc_ecc_bytes(chip->ecc.size,
                                                chip->ecc.strength);
diff --git a/drivers/mtd/nand/denali_pci.c b/drivers/mtd/nand/denali_pci.c
index a1ee9f8..a39682a5 100644
--- a/drivers/mtd/nand/denali_pci.c
+++ b/drivers/mtd/nand/denali_pci.c
@@ -87,6 +87,7 @@ static int denali_pci_probe(struct pci_dev *dev, const struct 
pci_device_id *id)
 
        denali->ecc_strength_avail = BIT(15) | BIT(8);
        denali->caps |= DENALI_CAP_ECC_SIZE_512;
+       denali->nand.ecc.options |= NAND_ECC_MAXIMIZE;
 
        ret = denali_init(denali);
        if (ret)
-- 
2.7.4

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