[PATCH] mtd: spi-nor: don't return found by JEDEC ID a non-JEDEC flash

[Vladimir Zapolskiy]

In attempt to spi_nor_scan() for an expected JEDEC compliant device by
reading RDID register don't return the first found non-JEDEC device
entry from spi_nor_ids[] table, if RDID is zero.

First of all zeroes in RDID may be evidence for not correctly working
SPI, secondly empty RDID can not be used to select a particular JEDEC
non-compliant device correctly.

The best possible solution is
* not to rely on spi_nor_read_id(), if expected device is non-JEDEC,
* not to substitute an expected JEDEC device with some arbitrary
  chosen non-JEDEC device, if RDID is zero.

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy at mentor.com>
---
 drivers/mtd/spi-nor/spi-nor.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index c51ee52..119ace9 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -661,6 +661,12 @@ static const struct spi_device_id *spi_nor_read_id(struct spi_nor *nor)
 
 	ext_jedec = id[3] << 8 | id[4];
 
+	/* Non-JEDEC flash memory can not be detected correctly */
+	if (!jedec && !ext_jedec) {
+		dev_err(nor->dev, "JEDEC compliant device is not found\n");
+		return ERR_PTR(-ENODEV);
+	}
+
 	for (tmp = 0; tmp < ARRAY_SIZE(spi_nor_ids) - 1; tmp++) {
 		info = (void *)spi_nor_ids[tmp].driver_data;
 		if (info->jedec_id == jedec) {
-- 
1.7.10.4