[PATCH v6 4/5] mtd: spi-nor: atmel: Fix unlock_all() for AT25FS010/040

[Michael Walle]

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.

Signed-off-by: Michael Walle <michael at walle.cc>
---
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..fe6a4653823d 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 behaviour 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)
+{
+	/* We only support unlocking the whole flash array */
+	if (ofs || len != nor->params->size)
+		return -EINVAL;
+
+	/*
+	 * Write 0x00 to the status register to try to disable the write
+	 * protection. This will fail if SRWD (the datasheet calls it WPEN) is
+	 * set. But there is nothing we can do.
+	 */
+	nor->bouncebuf[0] = 0;
+
+	return spi_nor_write_sr(nor, nor->bouncebuf, 1);
+}
+
+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 5bee7c8da4dc..8c06a28a90de 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -861,7 +861,7 @@ int spi_nor_wait_till_ready(struct spi_nor *nor)
  *
  * Return: 0 on success, -errno otherwise.
  */
-static int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len)
+int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len)
 {
 	int ret;
 
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 0a775a7b5606..16b350e1d865 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(struct spi_nor *nor, const u8 *sr, size_t len);
 
 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