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.

Going forward, DT platforms should specify "nand-ecc-strength" or
"nand-ecc-maximize" to show the ECC strength strategy explicitly.

If nothing is specified in DT, "nand-ecc-maximize" is implied since
this was the original behavior.  It applies to PCI platforms too.

Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com>
---

 .../devicetree/bindings/mtd/denali-nand.txt        |  5 ++++
 drivers/mtd/nand/denali.c                          | 27 +++++++++++++++++++++-
 drivers/mtd/nand/denali_pci.c                      |  2 ++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/mtd/denali-nand.txt 
b/Documentation/devicetree/bindings/mtd/denali-nand.txt
index e9d5818..51fe195 100644
--- a/Documentation/devicetree/bindings/mtd/denali-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/denali-nand.txt
@@ -9,6 +9,11 @@ Required properties:
 Optional properties:
   - nand-ecc-step-size: must be 512 or 1024.  If not specified, default to 512.
     see nand.txt for details.
+  - nand-ecc-strength: see nand.txt for details
+  - 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 54c9e0c..df174ca 100644
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -1393,6 +1393,21 @@ static int denali_set_max_ecc_strength(struct 
denali_nand_info *denali)
        return -EINVAL;
 }
 
+static int denali_check_ecc_strength(struct denali_nand_info *denali)
+{
+       const int *ecc_strength = denali->ecc_strength_avail;
+
+       for (; *ecc_strength; ecc_strength++) {
+               if (*ecc_strength == denali->nand.ecc.strength)
+                       return 0;
+       }
+
+       dev_err(denali->dev,
+               "Specified ECC strength is not supported for this 
controller.\n");
+
+       return -EINVAL;
+}
+
 static int denali_ooblayout_ecc(struct mtd_info *mtd, int section,
                                struct mtd_oob_region *oobregion)
 {
@@ -1628,7 +1643,17 @@ int denali_init(struct denali_nand_info *denali)
        if (!denali->ecc_strength_avail)
                denali->ecc_strength_avail = denali_default_ecc_strength;
 
-       ret = denali_set_max_ecc_strength(denali);
+       if (!chip->ecc.strength && !(chip->ecc.options & NAND_ECC_MAXIMIZE)) {
+               dev_info(denali->dev,
+                       "No ECC strength is specified.  Trying max ECC strength 
strategy\n");
+               chip->ecc.options |= NAND_ECC_MAXIMIZE;
+       }
+
+       if (chip->ecc.options & NAND_ECC_MAXIMIZE)
+               ret = denali_set_max_ecc_strength(denali);
+       else
+               ret = denali_check_ecc_strength(denali);
+
        if (ret)
                goto failed_req_irq;
 
diff --git a/drivers/mtd/nand/denali_pci.c b/drivers/mtd/nand/denali_pci.c
index ac84323..0064f3e 100644
--- a/drivers/mtd/nand/denali_pci.c
+++ b/drivers/mtd/nand/denali_pci.c
@@ -85,6 +85,8 @@ static int denali_pci_probe(struct pci_dev *dev, const struct 
pci_device_id *id)
                goto failed_remap_reg;
        }
 
+       denali->nand.ecc.options |= NAND_ECC_MAXIMIZE;
+
        ret = denali_init(denali);
        if (ret)
                goto failed_remap_mem;
-- 
2.7.4

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