From: White Ding <bpqw@xxxxxxxxxx>
Do nand reset before write protect check.
If we want to check the WP# low or high through STATUS READ and check bit 7,
we must reset the device, other operation (eg.erase/program a locked block) can
also clear the bit 7 of status register.
As we know the status register can be refreshed, if we do some operation to trigger it,
for example if we do erase/program operation to one block that is locked, then READ STATUS,
the bit 7 of READ STATUS will be 0 indicate the device in write protect, then if we do
erase/program operation to another block that is unlocked, the bit 7 of READ STATUS will
be 1 indicate the device is not write protect.
Suppose we checked the bit 7 of READ STATUS is 0 then judge the WP# is low (write protect),
but in this case the WP# maybe high if we do erase/program operation to a locked block,
so we must reset the device if we want to check the WP# low or high through STATUS READ and
check bit 7.
Signed-off-by: White Ding <bpqw@xxxxxxxxxx>
Signed-off-by: Brian Norris <computersforpeace@xxxxxxxxx>
[Cherry-picked from linux: 57d3a9a89a06 mtd: nand: fix nand_lock/unlock() function]
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
drivers/mtd/nand/nand_base.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ccf96150429a..128802fa5c20 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -852,6 +852,15 @@ int nand_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
chip->select_chip(mtd, chipnr);
+ /*
+ * Reset the chip.
+ * If we want to check the WP through READ STATUS and check the bit 7
+ * we must reset the chip
+ * some operation can also clear the bit 7 of status register
+ * eg. erase/program a locked block
+ */
+ chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
+
/* Check, if it is write protected */
if (nand_check_wp(mtd)) {
pr_debug("%s: device is write protected!\n",
@@ -902,6 +911,15 @@ int nand_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
chip->select_chip(mtd, chipnr);
+ /*
+ * Reset the chip.
+ * If we want to check the WP through READ STATUS and check the bit 7
+ * we must reset the chip
+ * some operation can also clear the bit 7 of status register
+ * eg. erase/program a locked block
+ */
+ chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
+
/* Check, if it is write protected */
if (nand_check_wp(mtd)) {
pr_debug("%s: device is write protected!\n",
--
2.19.1
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