[PATCH v2 34/46] mtd: nandsim: Support bitflip and read error emulation in file backend

[Daniel Walter]

From: Richard Weinberger <rich...@nod.at>

Since we don't track the empty state we have to check
whether the buffer is full with 0xff bytes or not.

Signed-off-by: Richard Weinberger <rich...@nod.at>
---
 drivers/mtd/nand/nandsim.c | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index 8cfdfea..185ca4d 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -1602,11 +1602,26 @@ static inline u_char *NS_PAGE_BYTE_OFF(struct nandsim 
*ns)
        return NS_GET_PAGE(ns)->byte + ns->regs.column + ns->regs.off;
 }
 
-static int do_read_error(struct nandsim *ns, int num)
+static bool buffer_is_ff(struct nandsim *ns, int num)
+{
+       int i;
+
+       for (i = 0; i < num; i++) {
+               if (ns->buf.byte[i] != 0xff)
+                       return false;
+       }
+
+       return true;
+}
+
+static int do_read_error(struct nandsim *ns, int num, bool check_ff)
 {
        unsigned int page_no = ns->regs.row;
 
        if (read_error(ns, page_no)) {
+               if (check_ff && buffer_is_ff(ns, num))
+                       return 0;
+
                prandom_bytes(ns->buf.byte, num);
                pr_warn("simulating read error in page %u\n", page_no);
                return 1;
@@ -1614,12 +1629,16 @@ static int do_read_error(struct nandsim *ns, int num)
        return 0;
 }
 
-static void do_bit_flips(struct nandsim *ns, int num)
+static void do_bit_flips(struct nandsim *ns, int num, bool check_ff)
 {
        struct mtd_info *nsmtd = ns_to_mtd(ns);
 
        if (ns->bitflips && prandom_u32() < (1 << 22)) {
                int flips = 1;
+
+               if (check_ff && buffer_is_ff(ns, num))
+                       return;
+
                if (ns->bitflips > 1)
                        flips = (prandom_u32() % (int)ns->bitflips) + 1;
                while (flips--) {
@@ -1644,10 +1663,10 @@ static void ns_ram_read_page(struct nandsim *ns, int 
num)
        } else {
                pr_debug("page %d allocated, reading from %d\n",
                        ns->regs.row, ns->regs.column + ns->regs.off);
-               if (do_read_error(ns, num))
+               if (do_read_error(ns, num, false))
                        return;
                memcpy(ns->buf.byte, NS_PAGE_BYTE_OFF(ns), num);
-               do_bit_flips(ns, num);
+               do_bit_flips(ns, num, false);
        }
 }
 
@@ -1664,7 +1683,7 @@ static void ns_cachefile_read_page(struct nandsim *ns, 
int num)
 
                pr_debug("page %d written, reading from %d\n",
                        ns->regs.row, ns->regs.column + ns->regs.off);
-               if (do_read_error(ns, num))
+               if (do_read_error(ns, num, false))
                        return;
                pos = (loff_t)NS_RAW_OFFSET(ns) + ns->regs.off;
                tx = read_file(ns, data->cfile, ns->buf.byte, num, pos);
@@ -1672,7 +1691,7 @@ static void ns_cachefile_read_page(struct nandsim *ns, 
int num)
                        pr_err("read error for page %d ret %ld\n", 
ns->regs.row, (long)tx);
                        return;
                }
-               do_bit_flips(ns, num);
+               do_bit_flips(ns, num, false);
        }
 }
 
@@ -1710,6 +1729,9 @@ void __ns_file_read_page(struct nandsim *ns, int num,
                memset(ns->buf.byte, 0xff, num);
        else if (tx != num)
                pr_err("read error for page %d ret %ld\n", ns->regs.row, 
(long)tx);
+
+       do_read_error(ns, num, true);
+       do_bit_flips(ns, num, true);
 }
 EXPORT_SYMBOL_GPL(__ns_file_read_page);
 
-- 
2.8.3