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mtd: nand: omap2: clean-up BCHx_HW and BCHx_SW ECC configurations in device_probe
current implementation in omap3_init_bch() has some redundant code like:
(1) omap3_init_bch() re-probes the DT-binding to detect presence of ELM h/w
engine on SoC. And based on that it selects implemetation of ecc-scheme.
However, this is already done as part of GPMC DT parsing.
(2) As omap3_init_bch() serves as common function for configuring all types of
BCHx ecc-schemes, so there are multiple levels of redudant if..then..else
checks while populating nand_chip->ecc.
This patch make following changes to OMAP NAND driver:
(1) removes omap3_init_bch(): each ecc-scheme is individually configured in
omap_nand_probe() there by removing redundant if..then..else checks.
(2) adds is_elm_present(): re-probing of ELM device via DT is not required as
it's done in GPMC driver probe. Thus is_elm_present() just initializes ELM
driver with NAND probe data, when ecc-scheme with h/w based error-detection
is used.
(3) separates out configuration of different flavours of "BCH4" and "BCH8"
ecc-schemes as given in below table
(4) conditionally compiles callbacks implementations of ecc.hwctl(),
ecc.calculate(), ecc.correct() to avoid warning of un-used functions.
+---------------------------------------+---------------+---------------+
| ECC scheme |ECC calculation|Error detection|
+---------------------------------------+---------------+---------------+
|OMAP_ECC_HAM1_CODE_HW |H/W (GPMC) |S/W |
+---------------------------------------+---------------+---------------+
|OMAP_ECC_BCH4_CODE_HW_DETECTION_SW |H/W (GPMC) |S/W (lib/bch.c)|
| (needs CONFIG_MTD_NAND_ECC_BCH) | | |
| | | |
|OMAP_ECC_BCH4_CODE_HW |H/W (GPMC) |H/W (ELM) |
| (needs CONFIG_MTD_NAND_OMAP_BCH && | | |
| ti,elm-id) | | |
+---------------------------------------+---------------+---------------+
|OMAP_ECC_BCH8_CODE_HW_DETECTION_SW |H/W (GPMC) |S/W (lib/bch.c)|
| (needs CONFIG_MTD_NAND_ECC_BCH) | | |
| | | |
|OMAP_ECC_BCH8_CODE_HW |H/W (GPMC) |H/W (ELM) |
| (needs CONFIG_MTD_NAND_OMAP_BCH && | | |
| ti,elm-id) | | |
+---------------------------------------+---------------+---------------+
- 'CONFIG_MTD_NAND_ECC_BCH' is generic KConfig required to build lib/bch.c
which is required for ECC error detection done in software.
(mainly used for legacy platforms which do not have on-chip ELM engine)
- 'CONFIG_MTD_NAND_OMAP_BCH' is OMAP specific Kconfig to detemine presence
on ELM h/w engine on SoC.
Signed-off-by: 
Pekon Gupta <pekon@ti.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>