Convert CONFIG_NAND_OMAP_ECCSCHEME to Kconfig

The values of CONFIG_NAND_OMAP_ECCSCHEME map to the enum in
include/linux/mtd/omap_gpmc.h for valid ECC schemes.  Make which one we
will use be a choice statement, enumerating the ones which we have
implemented.

Signed-off-by: Tom Rini <trini@konsulko.com>

1 files changed, 101 insertions, 2 deletions

diff --git a/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig
index 2e6fe14ab36..790ee344038 100644
--- a/drivers/mtd/nand/raw/Kconfig
+++ b/drivers/mtd/nand/raw/Kconfig
@@ -156,9 +156,10 @@ config NAND_OMAP_GPMC
 	  do ECC calculation (not ECC error detection) for HAM1, BCH4, BCH8
 	  and BCH16 ECC algorithms.
 
+if NAND_OMAP_GPMC
+
 config NAND_OMAP_GPMC_PREFETCH
 	bool "Enable GPMC Prefetch"
-	depends on NAND_OMAP_GPMC
 	default y
 	help
 	  On OMAP platforms that use the GPMC controller
@@ -167,7 +168,7 @@ config NAND_OMAP_GPMC_PREFETCH
 
 config NAND_OMAP_ELM
 	bool "Enable ELM driver for OMAPxx and AMxx platforms."
-	depends on NAND_OMAP_GPMC && !OMAP34XX
+	depends on !OMAP34XX
 	help
 	  ELM controller is used for ECC error detection (not ECC calculation)
 	  of BCH4, BCH8 and BCH16 ECC algorithms.
@@ -176,6 +177,104 @@ config NAND_OMAP_ELM
 	  detection. However ECC calculation on such plaforms would still be
 	  done by GPMC controller.
 
+choice
+	prompt "ECC scheme"
+	default NAND_OMAP_ECCSCHEME_BCH8_CODE_HW
+	help
+	On OMAP platforms, this CONFIG specifies NAND ECC scheme.
+	It can take following values:
+	OMAP_ECC_HAM1_CODE_SW
+		1-bit Hamming code using software lib.
+		(for legacy devices only)
+	OMAP_ECC_HAM1_CODE_HW
+		1-bit Hamming code using GPMC hardware.
+		(for legacy devices only)
+	OMAP_ECC_BCH4_CODE_HW_DETECTION_SW
+		4-bit BCH code (unsupported)
+	OMAP_ECC_BCH4_CODE_HW
+		4-bit BCH code (unsupported)
+	OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
+		8-bit BCH code with
+		- ecc calculation using GPMC hardware engine,
+		- error detection using software library.
+		- requires CONFIG_BCH to enable software BCH library
+		(For legacy device which do not have ELM h/w engine)
+	OMAP_ECC_BCH8_CODE_HW
+		8-bit BCH code with
+		- ecc calculation using GPMC hardware engine,
+		- error detection using ELM hardware engine.
+	OMAP_ECC_BCH16_CODE_HW
+		16-bit BCH code with
+		- ecc calculation using GPMC hardware engine,
+		- error detection using ELM hardware engine.
+
+	How to select ECC scheme on OMAP and AMxx platforms ?
+	-----------------------------------------------------
+	Though higher ECC schemes have more capability to detect and correct
+	bit-flips, but still selection of ECC scheme is dependent on following
+	- hardware engines present in SoC.
+		Some legacy OMAP SoC do not have ELM h/w engine thus such
+		SoC cannot support BCHx_HW ECC schemes.
+	- size of OOB/Spare region
+		With higher ECC schemes, more OOB/Spare area is required to
+		store ECC. So choice of ECC scheme is limited by NAND oobsize.
+
+	In general following expression can help:
+		NAND_OOBSIZE >= 2 + (NAND_PAGESIZE / 512) * ECC_BYTES
+	where
+		NAND_OOBSIZE	= number of bytes available in
+				OOB/spare area per NAND page.
+		NAND_PAGESIZE	= bytes in main-area of NAND page.
+		ECC_BYTES	= number of ECC bytes generated to
+				protect 512 bytes of data, which is:
+				3 for HAM1_xx ecc schemes
+				7 for BCH4_xx ecc schemes
+				14 for BCH8_xx ecc schemes
+				26 for BCH16_xx ecc schemes
+
+		example to check for BCH16 on 2K page NAND
+		NAND_PAGESIZE = 2048
+		NAND_OOBSIZE = 64
+		2 + (2048 / 512) * 26 = 106 > NAND_OOBSIZE
+		Thus BCH16 cannot be supported on 2K page NAND.
+
+		However, for 4K pagesize NAND
+		NAND_PAGESIZE = 4096
+		NAND_OOBSIZE = 224
+		ECC_BYTES = 26
+		2 + (4096 / 512) * 26 = 210 < NAND_OOBSIZE
+		Thus BCH16 can be supported on 4K page NAND.
+
+config NAND_OMAP_ECCSCHEME_HAM1_CODE_SW
+	bool "1-bit Hamming code using software lib"
+
+config NAND_OMAP_ECCSCHEME_HAM1_CODE_HW
+	bool "1-bit Hamming code using GPMC hardware"
+
+config NAND_OMAP_ECCSCHEME_BCH8_CODE_HW_DETECTION_SW
+	bool "8-bit BCH code with HW calculation SW error detection"
+
+config NAND_OMAP_ECCSCHEME_BCH8_CODE_HW
+	bool "8-bit BCH code with HW calculation and error detection"
+
+config NAND_OMAP_ECCSCHEME_BCH16_CODE_HW
+	bool "16-bit BCH code with HW calculation and error detection"
+
+endchoice
+
+config NAND_OMAP_ECCSCHEME
+	int
+	default 1 if NAND_OMAP_ECCSCHEME_HAM1_CODE_SW
+	default 2 if NAND_OMAP_ECCSCHEME_HAM1_CODE_HW
+	default 5 if NAND_OMAP_ECCSCHEME_BCH8_CODE_HW_DETECTION_SW
+	default 6 if NAND_OMAP_ECCSCHEME_BCH8_CODE_HW
+	default 7 if NAND_OMAP_ECCSCHEME_BCH16_CODE_HW
+	help
+	  This must be kept in sync with the enum in
+	  include/linux/mtd/omap_gpmc.h
+
+endif
+
 config NAND_VF610_NFC
 	bool "Support for Freescale NFC for VF610"
 	select SYS_NAND_SELF_INIT