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misc: mxc_ocotp: check fuse word before programming on i.MX7ULP

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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>
This commit is contained in:
Peng Fan 2018-01-02 15:51:20 +08:00 committed by Stefano Babic
parent fb8cac9366
commit 8df42bee0e
1 changed files with 17 additions and 0 deletions
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17
drivers/misc/mxc_ocotp.c
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@ -342,6 +342,23 @@ int fuse_sense(u32 bank, u32 word, u32 *val)
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);
}