ARM: OMAP3: gpmc: add BCH ecc api and modes

This patch adds a simple BCH ecc computation api, similar to the
existing Hamming ecc api. It is intended to be used by the MTD layer.
It implements the following features:

- support 4-bit and 8-bit ecc computation
- do not protect user bytes in spare area, only data area is protected
- ecc for an erased NAND page (0xFFs) is also a sequence of 0xFFs

This last feature is obtained by adding a constant polynomial to
the hardware computed ecc. It allows to correct bitflips in blank pages
and is extremely useful to support filesystems such as UBIFS, which expect
erased pages to contain only 0xFFs.

This api has been tested on an OMAP3630 board.

Artem: The OMAP maintainer Tony Lindgren gave us his blessing for merging
this patch via the MTD tree.

Signed-off-by: Ivan Djelic <ivan.djelic@parrot.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/arm/plat-omap/include/plat/gpmc.h b/arch/arm/plat-omap/include/plat/gpmc.h
index 1527929b445a..f37764a36072 100644
--- a/arch/arm/plat-omap/include/plat/gpmc.h
+++ b/arch/arm/plat-omap/include/plat/gpmc.h
@@ -92,6 +92,8 @@ enum omap_ecc {
         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 */
 };
 
 /*
@@ -157,4 +159,13 @@ extern int gpmc_nand_write(int cs, int cmd, int wval);
 
 int gpmc_enable_hwecc(int cs, int mode, int dev_width, int ecc_size);
 int gpmc_calculate_ecc(int cs, const u_char *dat, u_char *ecc_code);
+
+#ifdef CONFIG_ARCH_OMAP3
+int gpmc_init_hwecc_bch(int cs, int nsectors, int nerrors);
+int gpmc_enable_hwecc_bch(int cs, int mode, int dev_width, int nsectors,
+                          int nerrors);
+int gpmc_calculate_ecc_bch4(int cs, const u_char *dat, u_char *ecc);
+int gpmc_calculate_ecc_bch8(int cs, const u_char *dat, u_char *ecc);
+#endif /* CONFIG_ARCH_OMAP3 */
+
 #endif