From: "Gupta, Pekon" <pekon@xxxxxx>
ECC scheme on NAND devices can be implemented in multiple ways.Some using
Software algorithm, while others using in-build Hardware engines.
omap2-nand driver currently supports following flavours of ECC schemes,
selectable via DTB.
+---------------------------------------+---------------+---------------+
| ECC scheme |ECC calculation|Error detection|
+---------------------------------------+---------------+---------------+
|OMAP_ECC_HAMMING_CODE_DEFAULT |S/W |S/W |
|OMAP_ECC_HAMMING_CODE_HW |H/W (GPMC) |S/W |
|OMAP_ECC_HAMMING_CODE_HW_ROMCODE |H/W (GPMC) |S/W |
+---------------------------------------+---------------+---------------+
|(requires CONFIG_MTD_NAND_ECC_BCH) | | |
|OMAP_ECC_BCH8_CODE_HW_DETECTION_SW |H/W (GPMC) |S/W |
+---------------------------------------+---------------+---------------+
|(requires CONFIG_MTD_NAND_OMAP_BCH) | | |
|OMAP_ECC_BCH8_CODE_HW |H/W (GPMC) |H/W (ELM) |
+---------------------------------------+---------------+---------------+
Selection of some ECC schemes also require enabling following Kconfig options.
This was done to optimize footprint of omap2-nand driver.
-Kconfig:CONFIG_MTD_NAND_ECC_BCH enables S/W based BCH ECC algorithm
-Kconfig:CONFIG_MTD_NAND_OMAP_BCH enables H/W based BCH ECC algorithm
Signed-off-by: Gupta, Pekon <pekon@xxxxxx>
---
.../devicetree/bindings/mtd/gpmc-nand.txt | 37 +++++++++++++++-------
arch/arm/boot/dts/am335x-evm.dts | 2 +-
arch/arm/mach-omap2/gpmc.c | 12 ++++---
3 files changed, 34 insertions(+), 17 deletions(-)
diff --git a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
index e7f8d7e..de180be 100644
--- a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
@@ -17,20 +17,35 @@ Required properties:
Optional properties:
- - nand-bus-width: Set this numeric value to 16 if the hardware
- is wired that way. If not specified, a bus
- width of 8 is assumed.
+ - nand-bus-width: Determines data-width of the connected device
+ x16 = "16"
+ x8 = "8" (default)
- - ti,nand-ecc-opt: A string setting the ECC layout to use. One of:
- "sw" Software method (default)
- "hw" Hardware method
- "hw-romcode" gpmc hamming mode method & romcode layout
- "bch4" 4-bit BCH ecc code
- "bch8" 8-bit BCH ecc code
+ - ti,nand-ecc-opt: Determines the ECC scheme used by driver.
+ It can be any of the following strings:
+
+ "hamming_sw" 1-bit Hamming ECC using software
+
+ "hamming_hw" 1-bit Hamming ECC using hardware
+
+ "hamming_hw_romcode" 1-bit Hamming ECC using hardware
+ - ECC layout compatible to ROM code
+
+ "bch8_hw_detection_sw" 8-bit BCH with ECC calculation in hardware
+ and error detection in software
+ - requires Kconfig CONFIG_MTD_NAND_ECC_BCH
+
+ "bch8_hw" 8-bit BCH with ECC calculation in hardware
+ and error detection in hardware
+ - requires <elm_id> to be specified
+ - requires Kconfig CONFIG_MTD_NAND_OMAP_BCH
+
+
+
+ - elm_id: Specifies elm device node. This is required to
+ support some BCH ECC schemes mentioned above.
- - elm_id: Specifies elm device node. This is required to support BCH
- error correction using ELM module.
For inline partiton table parsing (optional):
diff --git a/arch/arm/boot/dts/am335x-evm.dts b/arch/arm/boot/dts/am335x-evm.dts
index 0b8f161..60e8f59 100644
--- a/arch/arm/boot/dts/am335x-evm.dts
+++ b/arch/arm/boot/dts/am335x-evm.dts
@@ -135,7 +135,7 @@
nand@0,0 {
reg = <0 0 0>; /* CS0, offset 0 */
nand-bus-width = <8>;
- ti,nand-ecc-opt = "bch8";
+ ti,nand-ecc-opt = "bch8_hw";
gpmc,sync-clk = <0>;
gpmc,cs-on = <0>;
diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
index 410e1ba..03b8027 100644
--- a/arch/arm/mach-omap2/gpmc.c
+++ b/arch/arm/mach-omap2/gpmc.c
@@ -1205,11 +1205,13 @@ static void __maybe_unused gpmc_read_timings_dt(struct device_node *np,
#ifdef CONFIG_MTD_NAND
static const char * const nand_ecc_opts[] = {
- [OMAP_ECC_HAMMING_CODE_DEFAULT] = "sw",
- [OMAP_ECC_HAMMING_CODE_HW] = "hw",
- [OMAP_ECC_HAMMING_CODE_HW_ROMCODE] = "hw-romcode",
- [OMAP_ECC_BCH4_CODE_HW] = "bch4",
- [OMAP_ECC_BCH8_CODE_HW] = "bch8",
+ [OMAP_ECC_HAMMING_CODE_DEFAULT] = "hamming_sw",
+ [OMAP_ECC_HAMMING_CODE_HW] = "hamming_hw",
+ [OMAP_ECC_HAMMING_CODE_HW_ROMCODE] = "hamming_hw_romcode",
+ [OMAP_ECC_BCH4_CODE_HW] = "bch4_hw",
+ [OMAP_ECC_BCH4_CODE_HW_DETECTION_SW] = "bch4_hw_detection_sw",
+ [OMAP_ECC_BCH8_CODE_HW] = "bch8_hw",
+ [OMAP_ECC_BCH8_CODE_HW_DETECTION_SW] = "bch8_hw_detection_sw"
};
static int gpmc_probe_nand_child(struct platform_device *pdev,
--
1.8.1
--
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