From 57d3a9a89a0645f3597561e214f8d6852a2c56b4 Mon Sep 17 00:00:00 2001 From: White Ding Date: Thu, 24 Jul 2014 00:10:45 +0800 Subject: [PATCH] mtd: nand: fix nand_lock/unlock() function 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 Signed-off-by: Brian Norris --- 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 d8cdf06343fb..1a27c2da29ff 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -982,6 +982,15 @@ 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", @@ -1032,6 +1041,15 @@ 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", -- 2.39.5