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>

1 files changed, 47 insertions, 18 deletions

diff --git a/drivers/mtd/tests/oobtest.c b/drivers/mtd/tests/oobtest.c
index edd859d96d85..1fd2cdad85f0 100644
--- 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");
                 }
         }