mtd: nand: omap: ecc.correct: omap_elm_correct_data: fix programmed-page bit-flip...

This patch updates following checks when bit-flips are detected by ELM:

 - Do not evaluate bit-flips when un-correctable bit-flips is reported by ELM,
   because as per [1] when ELM reports an un-correctable bit-flips,
   'number of error' field in its ELM_LOCATION_STATUS register is also invalid.

 - Return with error-code '-EBADMSG' on detection of un-correctable bit-flip.

 - Return with error-code '-EBADMSG' when bit-flips position is outside current
   Sector and OOB area.

[1] ELM IP spec Table-25 ELM_LOCATION_STATUS Register.
    ELM_LOCATION_STATUS[8] = ECC_CORRECTABLE: Error location process exit status
        0x0: ECC error location process failed.
             Number of errors and error locations are invalid.
        0x1: all errors were successfully located.
             Number of errors and error locations are valid.

Tested-by: Stefan Roese <sr@denx.de>
Signed-off-by: Pekon Gupta <pekon@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 39e3f50..4f067f0 100644 (file)
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1353,6 +1353,7 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
        int bitflip_count;
        bool is_error_reported = false;
        u32 bit_pos, byte_pos, error_max, pos;
+       int err;
 
        switch (info->ecc_opt) {
        case OMAP_ECC_BCH4_CODE_HW:
@@ -1434,8 +1435,12 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
        /* Decode BCH error using ELM module */
        elm_decode_bch_error_page(info->elm_dev, ecc_vec, err_vec);
 
+       err = 0;
        for (i = 0; i < eccsteps; i++) {
-               if (err_vec[i].error_reported) {
+               if (err_vec[i].error_uncorrectable) {
+                       pr_err("nand: uncorrectable bit-flips found\n");
+                       err = -EBADMSG;
+               } else if (err_vec[i].error_reported) {
                        for (j = 0; j < err_vec[i].error_count; j++) {
                                switch (info->ecc_opt) {
                                case OMAP_ECC_BCH4_CODE_HW:
@@ -1457,13 +1462,22 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
                                byte_pos = (error_max - pos - 1) / 8;
 
                                if (pos < error_max) {
-                                       if (byte_pos < 512)
+                                       if (byte_pos < 512) {
+                                               pr_debug("bitflip@dat[%d]=%x\n",
+                                                    byte_pos, data[byte_pos]);
                                                data[byte_pos] ^= 1 << bit_pos;
-                                       else
+                                       } else {
+                                               pr_debug("bitflip@oob[%d]=%x\n",
+                                                       (byte_pos - 512),
+                                                    spare_ecc[byte_pos - 512]);
                                                spare_ecc[byte_pos - 512] ^=
                                                        1 << bit_pos;
+                                       }
+                               } else {
+                                       pr_err("invalid bit-flip @ %d:%d\n",
+                                                        byte_pos, bit_pos);
+                                       err = -EBADMSG;
                                }
-                               /* else, not interested to correct ecc */
                        }
                }
 
@@ -1475,12 +1489,7 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
                spare_ecc += ecc->bytes;
        }
 
-       for (i = 0; i < eccsteps; i++)
-               /* Return error if uncorrectable error present */
-               if (err_vec[i].error_uncorrectable)
-                       return -EINVAL;
-
-       return stat;
+       return (err) ? err : stat;
 }
 
 /**