[PATCH v8 6/7] mtd: spi-nor: atmel: fix unlock_all() for AT25FS010/040

[Michael Walle <michael@walle.cc>]

These flashes have some weird BP bits mapping which aren't supported in
the current locking code. Just add a simple unlock op to unprotect the
entire flash array which is needed for legacy behavior.

Fixes: 3e0930f109e7 ("mtd: spi-nor: Rework the disabling of block write protection")
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
---
changes since v7:
 - added fixes tag

changes since v6:
 - use spi_nor_write_sr_and_check() and log a debug message if writing
   fails

changes since v5:
 - new patch

 drivers/mtd/spi-nor/atmel.c | 53 +++++++++++++++++++++++++++++++++++--
 drivers/mtd/spi-nor/core.c  |  2 +-
 drivers/mtd/spi-nor/core.h  |  1 +
 3 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/spi-nor/atmel.c b/drivers/mtd/spi-nor/atmel.c
index 49d392c6c8bc..deacf87a68a0 100644
--- a/drivers/mtd/spi-nor/atmel.c
+++ b/drivers/mtd/spi-nor/atmel.c
@@ -8,10 +8,59 @@
 
 #include "core.h"
 
+/*
+ * The Atmel AT25FS010/AT25FS040 parts have some weird configuration for the
+ * block protection bits. We don't support them. But legacy behavior in linux
+ * is to unlock the whole flash array on startup. Therefore, we have to support
+ * exactly this operation.
+ */
+static int atmel_at25fs_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	return -EOPNOTSUPP;
+}
+
+static int atmel_at25fs_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	int ret;
+
+	/* We only support unlocking the whole flash array */
+	if (ofs || len != nor->params->size)
+		return -EINVAL;
+
+	/* Write 0x00 to the status register to disable write protection */
+	ret = spi_nor_write_sr_and_check(nor, 0);
+	if (ret)
+		dev_dbg(nor->dev, "unable to clear BP bits, WP# asserted?\n");
+
+	return ret;
+}
+
+static int atmel_at25fs_is_locked(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct spi_nor_locking_ops atmel_at25fs_locking_ops = {
+	.lock = atmel_at25fs_lock,
+	.unlock = atmel_at25fs_unlock,
+	.is_locked = atmel_at25fs_is_locked,
+};
+
+static void atmel_at25fs_default_init(struct spi_nor *nor)
+{
+	nor->params->locking_ops = &atmel_at25fs_locking_ops;
+}
+
+static const struct spi_nor_fixups atmel_at25fs_fixups = {
+	.default_init = atmel_at25fs_default_init,
+};
+
 static const struct flash_info atmel_parts[] = {
 	/* Atmel -- some are (confusingly) marketed as "DataFlash" */
-	{ "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K | SPI_NOR_HAS_LOCK) },
-	{ "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK) },
+	{ "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K | SPI_NOR_HAS_LOCK)
+		.fixups = &atmel_at25fs_fixups },
+	{ "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK)
+		.fixups = &atmel_at25fs_fixups },
 
 	{ "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K | SPI_NOR_HAS_LOCK) },
 	{ "at25df321",  INFO(0x1f4700, 0, 64 * 1024,  64, SECT_4K | SPI_NOR_HAS_LOCK) },
diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 013198abe929..6afcb99e9741 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -1049,7 +1049,7 @@ static int spi_nor_write_16bit_cr_and_check(struct spi_nor *nor, u8 cr)
  *
  * Return: 0 on success, -errno otherwise.
  */
-static int spi_nor_write_sr_and_check(struct spi_nor *nor, u8 sr1)
+int spi_nor_write_sr_and_check(struct spi_nor *nor, u8 sr1)
 {
 	if (nor->flags & SNOR_F_HAS_16BIT_SR)
 		return spi_nor_write_16bit_sr_and_check(nor, sr1);
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 0a775a7b5606..7780169d485b 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -430,6 +430,7 @@ void spi_nor_unlock_and_unprep(struct spi_nor *nor);
 int spi_nor_sr1_bit6_quad_enable(struct spi_nor *nor);
 int spi_nor_sr2_bit1_quad_enable(struct spi_nor *nor);
 int spi_nor_sr2_bit7_quad_enable(struct spi_nor *nor);
+int spi_nor_write_sr_and_check(struct spi_nor *nor, u8 sr1);
 
 int spi_nor_xread_sr(struct spi_nor *nor, u8 *sr);
 ssize_t spi_nor_read_data(struct spi_nor *nor, loff_t from, size_t len,
-- 
2.20.1