[PATCH v5 1/4] ARM: OMAP2+: cleaned-up DT support of various ECC schemes

Pekon Gupta
2013-07-13T20:55:42Z

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: Pekon Gupta <pekon@ti.com>
---
.../devicetree/bindings/mtd/gpmc-nand.txt | 45 ++++++++++++++++------
arch/arm/mach-omap2/gpmc.c | 14 ++++---
include/linux/platform_data/mtd-nand-omap2.h | 22 +++++++----
3 files changed, 57 insertions(+), 24 deletions(-)

diff --git a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
index df338cb..c6551b6 100644
--- a/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/gpmc-nand.txt
@@ -17,17 +17,42 @@ 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_code_sw" 1-bit Hamming ECC
+ - ECC calculation in software
+ - Error detection in software
+
+ "hamming_code_hw" 1-bit Hamming ECC
+ - ECC calculation in hardware
+ - Error detection in software
+
+ "hamming_code_hw_romcode" 1-bit Hamming ECC
+ - ECC calculation in hardware
+ - Error detection in software
+ - ECC layout compatible to ROM code
+
+ "bch8_hw_code_detection_sw" 8-bit BCH ECC
+ - ECC calculation in hardware
+ - Error detection in software
+ - depends on CONFIG_MTD_NAND_ECC_BCH
+
+ "bch8_code_hw" 8-bit BCH ECC
+ - ECC calculation in hardware
+ - Error detection in hardware
+ - depends on CONFIG_MTD_NAND_OMAP_BCH
+ - requires <elm_id> to be specified
+
+
+ - elm_id: Specifies elm device node. This is required to
+ support some BCH ECC schemes mentioned above.
+

- ti,nand-xfer-type: A string setting the data transfer type. One of:

@@ -36,8 +61,6 @@ Optional properties:
"prefetch-dma" Prefetch enabled sDMA mode
"prefetch-irq" Prefetch enabled irq mode

- - 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/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
index 1c7969e..e19de21 100644
--- a/arch/arm/mach-omap2/gpmc.c
+++ b/arch/arm/mach-omap2/gpmc.c
@@ -1342,11 +1342,13 @@ 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_code_sw",
+ [OMAP_ECC_HAMMING_CODE_HW] = "hamming_code_hw",
+ [OMAP_ECC_HAMMING_CODE_HW_ROMCODE] = "hamming_code_hw_romcode",
+ [OMAP_ECC_BCH4_CODE_HW] = "bch4_code_hw",
+ [OMAP_ECC_BCH4_CODE_HW_DETECTION_SW] = "bch4_code_hw_detection_sw",
+ [OMAP_ECC_BCH8_CODE_HW] = "bch8_code_hw",
+ [OMAP_ECC_BCH8_CODE_HW_DETECTION_SW] = "bch8_code_hw_detection_sw"
};

static const char * const nand_xfer_types[] = {
@@ -1380,7 +1382,7 @@ static int gpmc_probe_nand_child(struct platform_device *pdev,

if (!of_property_read_string(child, "ti,nand-ecc-opt", &s))
for (val = 0; val < ARRAY_SIZE(nand_ecc_opts); val++)
- if (!strcasecmp(s, nand_ecc_opts[val])) {
+ if (!strcmp(s, nand_ecc_opts[val])) {
gpmc_nand_data->ecc_opt = val;
break;
}
diff --git a/include/linux/platform_data/mtd-nand-omap2.h b/include/linux/platform_data/mtd-nand-omap2.h
index 6bf9ef4..ce74576 100644
--- a/include/linux/platform_data/mtd-nand-omap2.h
+++ b/include/linux/platform_data/mtd-nand-omap2.h
@@ -23,13 +23,21 @@ enum nand_io {
};

enum omap_ecc {
- /* 1-bit ecc: stored at end of spare area */
- OMAP_ECC_HAMMING_CODE_DEFAULT = 0, /* Default, s/w method */
- OMAP_ECC_HAMMING_CODE_HW, /* gpmc to detect the error */
- /* 1-bit ecc: stored at beginning of spare area as romcode */
- OMAP_ECC_HAMMING_CODE_HW_ROMCODE, /* gpmc method & romcode layout */
- OMAP_ECC_BCH4_CODE_HW, /* 4-bit BCH ecc code */
- OMAP_ECC_BCH8_CODE_HW, /* 8-bit BCH ecc code */
+ /* 1-bit ECC calculation by Software, Error detection by Software */
+ OMAP_ECC_HAMMING_CODE_DEFAULT = 0,
+ /* 1-bit ECC calculation by GPMC, Error detection by Software */
+ OMAP_ECC_HAMMING_CODE_HW,
+ /* 1-bit ECC calculation by GPMC, Error detection by Software */
+ /* ECC layout compatible to legacy ROMCODE. */
+ OMAP_ECC_HAMMING_CODE_HW_ROMCODE,
+ /* 4-bit ECC calculation by GPMC, Error detection by ELM */
+ OMAP_ECC_BCH4_CODE_HW,
+ /* 4-bit ECC calculation by GPMC, Error detection by Software */
+ OMAP_ECC_BCH4_CODE_HW_DETECTION_SW,
+ /* 8-bit ECC calculation by GPMC, Error detection by ELM */
+ OMAP_ECC_BCH8_CODE_HW,
+ /* 8-bit ECC calculation by GPMC, Error detection by Software */
+ OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
};

struct gpmc_nand_regs {
--
1.8.1