[MTD] [NAND] nand_ecc.c: adding support for 512 byte ecc

Support 512 byte ECC calculation

[FM: updated two comments]

Signed-off-by: Vimal Singh <vimalsingh@ti.com>
Signed-off-by: Frans Meulenbroeks <fransmeulenbroeks@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 62 insertions, 24 deletions

diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c
index fd19787c9ce7..868147acce2c 100644
--- a/drivers/mtd/nand/nand_ecc.c
+++ b/drivers/mtd/nand/nand_ecc.c
@@ -42,6 +42,8 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/nand.h>
 #include <linux/mtd/nand_ecc.h>
 #include <asm/byteorder.h>
 #else
@@ -148,8 +150,9 @@ static const char addressbits[256] = {
 };
 
 /**
- * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
- * @mtd:        MTD block structure (unused)
+ * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256/512-byte
+ *                       block
+ * @mtd:        MTD block structure
  * @buf:        input buffer with raw data
  * @code:       output buffer with ECC
  */
@@ -158,13 +161,18 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
 {
         int i;
         const uint32_t *bp = (uint32_t *)buf;
+        /* 256 or 512 bytes/ecc  */
+        const uint32_t eccsize_mult =
+                        (((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
         uint32_t cur;           /* current value in buffer */
-        /* rp0..rp15 are the various accumulated parities (per byte) */
+        /* rp0..rp15..rp17 are the various accumulated parities (per byte) */
         uint32_t rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
-        uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
+        uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15, rp16;
+        uint32_t uninitialized_var(rp17);       /* to make compiler happy */
         uint32_t par;           /* the cumulative parity for all data */
         uint32_t tmppar;        /* the cumulative parity for this iteration;
-                                   for rp12 and rp14 at the end of the loop */
+                                   for rp12, rp14 and rp16 at the end of the
+                                   loop */
 
         par = 0;
         rp4 = 0;
@@ -173,6 +181,7 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
         rp10 = 0;
         rp12 = 0;
         rp14 = 0;
+        rp16 = 0;
 
         /*
          * The loop is unrolled a number of times;
@@ -181,10 +190,10 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
          * Note: passing unaligned data might give a performance penalty.
          * It is assumed that the buffers are aligned.
          * tmppar is the cumulative sum of this iteration.
-         * needed for calculating rp12, rp14 and par
+         * needed for calculating rp12, rp14, rp16 and par
          * also used as a performance improvement for rp6, rp8 and rp10
          */
-        for (i = 0; i < 4; i++) {
+        for (i = 0; i < eccsize_mult << 2; i++) {
                 cur = *bp++;
                 tmppar = cur;
                 rp4 ^= cur;
@@ -247,12 +256,14 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
                         rp12 ^= tmppar;
                 if ((i & 0x2) == 0)
                         rp14 ^= tmppar;
+                if (eccsize_mult == 2 && (i & 0x4) == 0)
+                        rp16 ^= tmppar;
         }
 
         /*
          * handle the fact that we use longword operations
-         * we'll bring rp4..rp14 back to single byte entities by shifting and
-         * xoring first fold the upper and lower 16 bits,
+         * we'll bring rp4..rp14..rp16 back to single byte entities by
+         * shifting and xoring first fold the upper and lower 16 bits,
          * then the upper and lower 8 bits.
          */
         rp4 ^= (rp4 >> 16);
@@ -273,6 +284,11 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
         rp14 ^= (rp14 >> 16);
         rp14 ^= (rp14 >> 8);
         rp14 &= 0xff;
+        if (eccsize_mult == 2) {
+                rp16 ^= (rp16 >> 16);
+                rp16 ^= (rp16 >> 8);
+                rp16 &= 0xff;
+        }
 
         /*
          * we also need to calculate the row parity for rp0..rp3
@@ -315,7 +331,7 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
         par &= 0xff;
 
         /*
-         * and calculate rp5..rp15
+         * and calculate rp5..rp15..rp17
          * note that par = rp4 ^ rp5 and due to the commutative property
          * of the ^ operator we can say:
          * rp5 = (par ^ rp4);
@@ -329,6 +345,8 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
         rp11 = (par ^ rp10) & 0xff;
         rp13 = (par ^ rp12) & 0xff;
         rp15 = (par ^ rp14) & 0xff;
+        if (eccsize_mult == 2)
+                rp17 = (par ^ rp16) & 0xff;
 
         /*
          * Finally calculate the ecc bits.
@@ -375,32 +393,46 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
             (invparity[rp9] << 1)  |
             (invparity[rp8]);
 #endif
-        code[2] =
-            (invparity[par & 0xf0] << 7) |
-            (invparity[par & 0x0f] << 6) |
-            (invparity[par & 0xcc] << 5) |
-            (invparity[par & 0x33] << 4) |
-            (invparity[par & 0xaa] << 3) |
-            (invparity[par & 0x55] << 2) |
-            3;
+        if (eccsize_mult == 1)
+                code[2] =
+                    (invparity[par & 0xf0] << 7) |
+                    (invparity[par & 0x0f] << 6) |
+                    (invparity[par & 0xcc] << 5) |
+                    (invparity[par & 0x33] << 4) |
+                    (invparity[par & 0xaa] << 3) |
+                    (invparity[par & 0x55] << 2) |
+                    3;
+        else
+                code[2] =
+                    (invparity[par & 0xf0] << 7) |
+                    (invparity[par & 0x0f] << 6) |
+                    (invparity[par & 0xcc] << 5) |
+                    (invparity[par & 0x33] << 4) |
+                    (invparity[par & 0xaa] << 3) |
+                    (invparity[par & 0x55] << 2) |
+                    (invparity[rp17] << 1) |
+                    (invparity[rp16] << 0);
         return 0;
 }
 EXPORT_SYMBOL(nand_calculate_ecc);
 
 /**
  * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
- * @mtd:        MTD block structure (unused)
+ * @mtd:        MTD block structure
  * @buf:        raw data read from the chip
  * @read_ecc:   ECC from the chip
  * @calc_ecc:   the ECC calculated from raw data
  *
- * Detect and correct a 1 bit error for 256 byte block
+ * Detect and correct a 1 bit error for 256/512 byte block
  */
 int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
                       unsigned char *read_ecc, unsigned char *calc_ecc)
 {
         unsigned char b0, b1, b2;
         unsigned char byte_addr, bit_addr;
+        /* 256 or 512 bytes/ecc  */
+        const uint32_t eccsize_mult =
+                        (((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
 
         /*
          * b0 to b2 indicate which bit is faulty (if any)
@@ -426,10 +458,12 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
 
         if ((((b0 ^ (b0 >> 1)) & 0x55) == 0x55) &&
             (((b1 ^ (b1 >> 1)) & 0x55) == 0x55) &&
-            (((b2 ^ (b2 >> 1)) & 0x54) == 0x54)) { /* single bit error */
+            ((eccsize_mult == 1 && ((b2 ^ (b2 >> 1)) & 0x54) == 0x54) ||
+             (eccsize_mult == 2 && ((b2 ^ (b2 >> 1)) & 0x55) == 0x55))) {
+        /* single bit error */
                 /*
-                 * rp15/13/11/9/7/5/3/1 indicate which byte is the faulty byte
-                 * cp 5/3/1 indicate the faulty bit.
+                 * rp17/rp15/13/11/9/7/5/3/1 indicate which byte is the faulty
+                 * byte, cp 5/3/1 indicate the faulty bit.
                  * A lookup table (called addressbits) is used to filter
                  * the bits from the byte they are in.
                  * A marginal optimisation is possible by having three
@@ -443,7 +477,11 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
                  * We could also do addressbits[b2] >> 1 but for the
                  * performace it does not make any difference
                  */
-                byte_addr = (addressbits[b1] << 4) + addressbits[b0];
+                if (eccsize_mult == 1)
+                        byte_addr = (addressbits[b1] << 4) + addressbits[b0];
+                else
+                        byte_addr = (addressbits[b2 & 0x3] << 8) +
+                                    (addressbits[b1] << 4) + addressbits[b0];
                 bit_addr = addressbits[b2 >> 2];
                 /* flip the bit */
                 buf[byte_addr] ^= (1 << bit_addr);