From 3f719069c884284b2457448a7afe32b02bd4f782 Mon Sep 17 00:00:00 2001 From: pekon gupta Date: Mon, 18 Nov 2013 19:03:01 +0530 Subject: mtd: nand: omap: add CONFIG_NAND_OMAP_ECCSCHEME for selection of ecc-scheme This patch adds new CONFIG_NAND_OMAP_ECCSCHEME, replacing other distributed CONFIG_xx used for selecting NAND ecc-schemes. This patch aims at solving following issues. 1) Currently ecc-scheme is tied to SoC platform, which prevents user to select other ecc-schemes also supported in hardware. like; - most of OMAP3 SoC platforms use only 1-bit Hamming ecc-scheme, inspite the fact that they can use higher ecc-schemes like 8-bit ecc-schemes with software based error detection (OMAP_ECC_BCH4_CODE_HW_DETECTION_SW). - most of AM33xx SoC plaforms use 8-bit BCH ecc-scheme for now, but hardware supports BCH16 ecc-scheme also. 2) Different platforms use different CONFIG_xx to select ecc-schemes, which adds confusion for user while migrating platforms. - *CONFIG_NAND_OMAP_ELM* which enables ELM hardware engine, selects only 8-bit BCH ecc-scheme with h/w based error-correction (OMAP_ECC_BCH8_CODE_HW) whereas ELM hardware engine supports other ecc-schemes also like; BCH4, and BCH16 (in future). - *CONFIG_NAND_OMAP_BCH8* selects 8-bit BCH ecc-scheme with s/w based error correction (OMAP_ECC_BCH8_CODE_HW_DETECTION_SW). - *CONFIG_SPL_NAND_SOFTECC* selects 1-bit Hamming ecc-scheme using s/w library Thus adding new *CONFIG_NAND_OMAP_ECCSCHEME* de-couples ecc-scheme dependency on SoC platform and NAND driver. And user can select ecc-scheme independently foreach board. However, selection some hardware based ecc-schemes (OMAP_ECC_BCHx_CODE_HW) still depends on presence of ELM hardware engine on SoC. (Refer doc/README.nand) Signed-off-by: Pekon Gupta --- doc/README.nand | 23 +++++++++++++++++++++++ doc/README.omap3 | 3 +-- 2 files changed, 24 insertions(+), 2 deletions(-) (limited to 'doc') diff --git a/doc/README.nand b/doc/README.nand index 487548f..b91f198 100644 --- a/doc/README.nand +++ b/doc/README.nand @@ -208,6 +208,29 @@ Platform specific options detection. However ECC calculation on such plaforms would still be done by GPMC controller. + CONFIG_NAND_OMAP_ECCSCHEME + 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. NOTE: ===== diff --git a/doc/README.omap3 b/doc/README.omap3 index 1fbe79d..a62c357 100644 --- a/doc/README.omap3 +++ b/doc/README.omap3 @@ -161,8 +161,7 @@ BCH8 To enable hardware assisted BCH8 (8-bit BCH [Bose, Chaudhuri, Hocquenghem]) on OMAP3 devices we can use the BCH library in lib/bch.c. To do so add CONFIG_BCH -to enable the library and CONFIG_NAND_OMAP_BCH8 to to enable hardware assisted -syndrom generation to your board config. +and set CONFIG_NAND_OMAP_ECCSCHEME=5 (refer README.nand) for selecting BCH8_SW. The NAND OOB layout is the same as in linux kernel, if the linux kernel BCH8 implementation for OMAP3 works for you so the u-boot version should also. When you require the SPL to read with BCH8 there are two more configs to -- cgit v1.1