The status register bit SRWD (status register write disable) is
described in many words in the datasheets but effectively boils down to:
i) if set, respect WP# when trying to change protection bits;
ii) if unset, ignore WP# when trying to change protection bits
In short, the bit determines whether the WP# signal is honored or not.
It's difficult to imagine the use-case where the WP# is connected and
asserted but the user doesn't want to respect its setting. As such,
this patch sets the SRWD bit unconditionally so that the WP# is _always_
respected; hardware that doesn't care about WP# normally won't even have
it connected.
Tested on a Cypress s25fl512s. With this patch, the WP# is always
respected, irregardless of whether any flash protection bits are set.
Signed-off-by: Jonas Bonn <jo...@norrbonn.se>
CC: Marek Vasut <marek.va...@gmail.com>
CC: David Woodhouse <dw...@infradead.org>
CC: Brian Norris <computersforpe...@gmail.com>
CC: Boris Brezillon <bbrezil...@kernel.org>
CC: Richard Weinberger <rich...@nod.at>
CC: linux-...@lists.infradead.org
---
drivers/mtd/spi-nor/spi-nor.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index c6064479b614..c960c097e0bc 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1230,9 +1230,6 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs,
uint64_t len)
status_new = (status_old & ~mask & ~SR_TB) | val;
- /* Disallow further writes if WP pin is asserted */
- status_new |= SR_SRWD;
-
if (!use_top)
status_new |= SR_TB;
@@ -1312,10 +1309,6 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs,
uint64_t len)
status_new = (status_old & ~mask & ~SR_TB) | val;
- /* Don't protect status register if we're fully unlocked */
- if (lock_len == 0)
- status_new &= ~SR_SRWD;
-
if (!use_top)
status_new |= SR_TB;
@@ -3918,6 +3911,7 @@ static int spi_nor_setup(struct spi_nor *nor,
static int spi_nor_init(struct spi_nor *nor)
{
int err;
+ int sr;
/*
* Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
@@ -3953,6 +3947,16 @@ static int spi_nor_init(struct spi_nor *nor)
set_4byte(nor, true);
}
+ /* Always respect the WP# (write-protect) input */
+ sr = read_sr(nor);
+ if (sr < 0) {
+ dev_err(nor->dev, "error while reading status register\n");
+ return -EINVAL;
+ }
+ sr |= SR_SRWD;
+ return write_sr_and_check(nor, sr, SR_SRWD);
+
+
return 0;
}
--
2.19.1
