mtd: mtd_oobtest: add bitflip_limit parameter

It is common for NAND devices to have bitflip errors.
Add a bitflip_limit parameter to specify how many bitflips per
page we can tolerate without flagging an error.
By default zero bitflips are tolerated.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --git a/drivers/mtd/tests/oobtest.c b/drivers/mtd/tests/oobtest.c
index edd859d..1fd2cda 100644 (file)
--- a/drivers/mtd/tests/oobtest.c
+++ b/drivers/mtd/tests/oobtest.c
@@ -34,8 +34,11 @@
 #include "mtd_test.h"
 
 static int dev = -EINVAL;
+static int bitflip_limit;
 module_param(dev, int, S_IRUGO);
 MODULE_PARM_DESC(dev, "MTD device number to use");
+module_param(bitflip_limit, int, S_IRUGO);
+MODULE_PARM_DESC(bitflip_limit, "Max. allowed bitflips per page");
 
 static struct mtd_info *mtd;
 static unsigned char *readbuf;
@@ -115,24 +118,27 @@ static int write_whole_device(void)
        return 0;
 }
 
-/* Display the address, offset and data bytes at comparison failure */
-static int memcmpshow(loff_t addr, const void *cs, const void *ct, size_t count)
+/*
+ * Display the address, offset and data bytes at comparison failure.
+ * Return number of bitflips encountered.
+ */
+static size_t memcmpshow(loff_t addr, const void *cs, const void *ct, size_t count)
 {
        const unsigned char *su1, *su2;
        int res;
-       int ret = 0;
        size_t i = 0;
+       size_t bitflips = 0;
 
        for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--, i++) {
                res = *su1 ^ *su2;
                if (res) {
                        pr_info("error @addr[0x%lx:0x%x] 0x%x -> 0x%x diff 0x%x\n",
                                (unsigned long)addr, i, *su1, *su2, res);
-                       ret = 1;
+                       bitflips += hweight8(res);
                }
        }
 
-       return ret;
+       return bitflips;
 }
 
 static int verify_eraseblock(int ebnum)
@@ -141,6 +147,7 @@ static int verify_eraseblock(int ebnum)
        struct mtd_oob_ops ops;
        int err = 0;
        loff_t addr = (loff_t)ebnum * mtd->erasesize;
+       size_t bitflips;
 
        prandom_bytes_state(&rnd_state, writebuf, use_len_max * pgcnt);
        for (i = 0; i < pgcnt; ++i, addr += mtd->writesize) {
@@ -159,9 +166,11 @@ static int verify_eraseblock(int ebnum)
                        errcnt += 1;
                        return err ? err : -1;
                }
-               if (memcmpshow(addr, readbuf,
-                              writebuf + (use_len_max * i) + use_offset,
-                              use_len)) {
+
+               bitflips = memcmpshow(addr, readbuf,
+                                     writebuf + (use_len_max * i) + use_offset,
+                                     use_len);
+               if (bitflips > bitflip_limit) {
                        pr_err("error: verify failed at %#llx\n",
                               (long long)addr);
                        errcnt += 1;
@@ -169,7 +178,10 @@ static int verify_eraseblock(int ebnum)
                                pr_err("error: too many errors\n");
                                return -1;
                        }
+               } else if (bitflips) {
+                       pr_info("ignoring error as within bitflip_limit\n");
                }
+
                if (use_offset != 0 || use_len < mtd->ecclayout->oobavail) {
                        int k;
 
@@ -188,9 +200,10 @@ static int verify_eraseblock(int ebnum)
                                errcnt += 1;
                                return err ? err : -1;
                        }
-                       if (memcmpshow(addr, readbuf + use_offset,
-                                      writebuf + (use_len_max * i) + use_offset,
-                                      use_len)) {
+                       bitflips = memcmpshow(addr, readbuf + use_offset,
+                                             writebuf + (use_len_max * i) + use_offset,
+                                             use_len);
+                       if (bitflips > bitflip_limit) {
                                pr_err("error: verify failed at %#llx\n",
                                                (long long)addr);
                                errcnt += 1;
@@ -198,7 +211,10 @@ static int verify_eraseblock(int ebnum)
                                        pr_err("error: too many errors\n");
                                        return -1;
                                }
+                       } else if (bitflips) {
+                               pr_info("ignoring error as within bitflip_limit\n");
                        }
+
                        for (k = 0; k < use_offset; ++k)
                                if (readbuf[k] != 0xff) {
                                        pr_err("error: verify 0xff "
@@ -237,6 +253,9 @@ static int verify_eraseblock_in_one_go(int ebnum)
        int err = 0;
        loff_t addr = (loff_t)ebnum * mtd->erasesize;
        size_t len = mtd->ecclayout->oobavail * pgcnt;
+       size_t oobavail = mtd->ecclayout->oobavail;
+       size_t bitflips;
+       int i;
 
        prandom_bytes_state(&rnd_state, writebuf, len);
        ops.mode      = MTD_OPS_AUTO_OOB;
@@ -247,6 +266,8 @@ static int verify_eraseblock_in_one_go(int ebnum)
        ops.ooboffs   = 0;
        ops.datbuf    = NULL;
        ops.oobbuf    = readbuf;
+
+       /* read entire block's OOB at one go */
        err = mtd_read_oob(mtd, addr, &ops);
        if (err || ops.oobretlen != len) {
                pr_err("error: readoob failed at %#llx\n",
@@ -254,13 +275,21 @@ static int verify_eraseblock_in_one_go(int ebnum)
                errcnt += 1;
                return err ? err : -1;
        }
-       if (memcmpshow(addr, readbuf, writebuf, len)) {
-               pr_err("error: verify failed at %#llx\n",
-                      (long long)addr);
-               errcnt += 1;
-               if (errcnt > 1000) {
-                       pr_err("error: too many errors\n");
-                       return -1;
+
+       /* verify one page OOB at a time for bitflip per page limit check */
+       for (i = 0; i < pgcnt; ++i, addr += mtd->writesize) {
+               bitflips = memcmpshow(addr, readbuf + (i * oobavail),
+                                     writebuf + (i * oobavail), oobavail);
+               if (bitflips > bitflip_limit) {
+                       pr_err("error: verify failed at %#llx\n",
+                              (long long)addr);
+                       errcnt += 1;
+                       if (errcnt > 1000) {
+                               pr_err("error: too many errors\n");
+                               return -1;
+                       }
+               } else if (bitflips) {
+                       pr_info("ignoring error as within bitflip_limit\n");
                }
        }