mtd: spi-nor: add generic flash driver

Our SFDP parsing is everything we need to support all basic operations
of a flash device. If the flash isn't found in our in-kernel flash
database, gracefully fall back to a driver described solely by its SFDP
tables.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Tested-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Link: https://lore.kernel.org/r/20220810220654.1297699-7-michael@walle.cc

1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index 15fb7f661ae9..c88628e8ee4e 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -1257,6 +1257,33 @@ static void spi_nor_post_sfdp_fixups(struct spi_nor *nor)
 }
 
 /**
+ * spi_nor_check_sfdp_signature() - check for a valid SFDP signature
+ * @nor:	pointer to a 'struct spi_nor'
+ *
+ * Used to detect if the flash supports the RDSFDP command as well as the
+ * presence of a valid SFDP table.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+int spi_nor_check_sfdp_signature(struct spi_nor *nor)
+{
+	u32 signature;
+	int err;
+
+	/* Get the SFDP header. */
+	err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sizeof(signature),
+					   &signature);
+	if (err < 0)
+		return err;
+
+	/* Check the SFDP signature. */
+	if (le32_to_cpu(signature) != SFDP_SIGNATURE)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
  * spi_nor_parse_sfdp() - parse the Serial Flash Discoverable Parameters.
  * @nor:		pointer to a 'struct spi_nor'
  *