mtd: gpmi: add a new DT property to use the datasheet's minimum required ECC

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=89b59e6cc15db8cea20a0c0aac18548bccfcb5f9
Commit:     89b59e6cc15db8cea20a0c0aac18548bccfcb5f9
Parent:     43b77693be6d222561283adfcd06ec3813770ea4
Author:     Huang Shijie <b32955 at freescale.com>
AuthorDate: Thu Nov 7 18:07:38 2013 +0800
Committer:  Brian Norris <computersforpeace at gmail.com>
CommitDate: Fri Jan 3 11:22:08 2014 -0800

    mtd: gpmi: add a new DT property to use the datasheet's minimum required ECC
    
    In default way, we use the ecc_strength/ecc_step size calculated by ourselves
    and use all the OOB area.
    
    This patch adds a new property : "fsl,use-minimum-ecc"
    
    If we enable it, we will firstly try to use the datasheet's minimum required
    ECC provided by the MTD layer (the ecc_strength_ds/ecc_step_ds fields
    in the nand_chip{}). So we may have free space in the OOB area by using the
    minimum ECC, and we may support JFFS2 with some SLC NANDs, such as Micron's
    SLC NAND.
    
    If we fail to use the minimum ECC, we will use the legacy method to calculate
    the ecc_strength and ecc_step size.
    
    Signed-off-by: Huang Shijie <b32955 at freescale.com>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 Documentation/devicetree/bindings/mtd/gpmi-nand.txt | 8 ++++++++
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c              | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/mtd/gpmi-nand.txt b/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
index 551b2a1..458d596 100644
--- a/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
@@ -17,6 +17,14 @@ Required properties:
 Optional properties:
   - nand-on-flash-bbt: boolean to enable on flash bbt option if not
                        present false
+  - fsl,use-minimum-ecc: Protect this NAND flash with the minimum ECC
+                       strength required. The required ECC strength is
+                       automatically discoverable for some flash
+                       (e.g., according to the ONFI standard).
+                       However, note that if this strength is not
+                       discoverable or this property is not enabled,
+                       the software may chooses an implementation-defined
+                       ECC scheme.
 
 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/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index dabbc14..9c59116 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -352,6 +352,9 @@ static int legacy_set_geometry(struct gpmi_nand_data *this)
 
 int common_nfc_set_geometry(struct gpmi_nand_data *this)
 {
+	if (of_property_read_bool(this->dev->of_node, "fsl,use-minimum-ecc")
+		&& set_geometry_by_ecc_info(this))
+		return 0;
 	return legacy_set_geometry(this);
 }