[PATCH 1/2] mtd: spi-nor: Fix RDCR controller capability core check

[Miquel Raynal]

Commit 5008c3ec3f89 ("mtd: spi-nor: core: Check read CR support") adds a
controller check to make sure the core will not use CR reads on
controllers not supporting them. The approach is valid but the fix is
incorrect. Unfortunately, the author could not catch it, because the
expected behavior was met. The patch indeed drops the RDCR capability,
but it does it for all controllers!

The issue comes from the use of spi_nor_spimem_check_op() which is an
internal helper dedicated to check page operations, ie. it is only used
for page reads and page programs (despite its generic name).

This helper looks for the biggest number of address bytes that can be
used for a page operation and tries 4 then 3. It then calls the usual
spi-mem helpers to do the checks. These will always fail because there
is now an inconsistency: the address cycles are forced to 4 (then 3)
bytes, but the bus width during the address cycles rightfully remains 0:
impossible, the operation is invalid.

The correct check in this case is to directly call spi_mem_supports_op()
which doesn't messes up with the operation content.

Fixes: 5008c3ec3f89 ("mtd: spi-nor: core: Check read CR support")
Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 drivers/mtd/spi-nor/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index d3f8a78efd3b..1f2e312feec7 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -2466,7 +2466,7 @@ spi_nor_spimem_adjust_hwcaps(struct spi_nor *nor, u32 *hwcaps)
 
 		spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
 
-		if (spi_nor_spimem_check_op(nor, &op))
+		if (!spi_mem_supports_op(nor->spimem, &op))
 			nor->flags |= SNOR_F_NO_READ_CR;
 	}
 }
-- 
2.51.1