misc: mxc_ocotp: check fuse word before programming on i.MX7ULP
On i.MX7ULP, the fuse words (except bank 0 and 1) only supports to
write once, because they use ECC mode. Multiple writes may damage
the ECC value and cause a wrong fuse value decoded when reading.
This patch adds a checking before the fuse word programming, only
can write when the word value is 0.
Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/misc/mxc_ocotp.c b/drivers/misc/mxc_ocotp.c
index 8986bb4..18a2730 100644
--- a/drivers/misc/mxc_ocotp.c
+++ b/drivers/misc/mxc_ocotp.c
@@ -342,6 +342,23 @@
static int prepare_write(struct ocotp_regs **regs, u32 bank, u32 word,
const char *caller)
{
+#ifdef CONFIG_MX7ULP
+ u32 val;
+ int ret;
+
+ /* Only bank 0 and 1 are redundancy mode, others are ECC mode */
+ if (bank != 0 && bank != 1) {
+ ret = fuse_sense(bank, word, &val);
+ if (ret)
+ return ret;
+
+ if (val != 0) {
+ printf("mxc_ocotp: The word has been programmed, no more write\n");
+ return -EPERM;
+ }
+ }
+#endif
+
return prepare_access(regs, bank, word, true, caller);
}