linux-kernel - [PATCH] mtd: spi-nor: Fix 3-or-4 address byte mode logic

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Date:   Thu,  1 Oct 2020 01:56:11 +0200
From:   Bert Vermeulen <bert@...t.com>
To:     tudor.ambarus@...rochip.com, miquel.raynal@...tlin.com,
        richard@....at, vigneshr@...com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Bert Vermeulen <bert@...t.com>
Subject: [PATCH] mtd: spi-nor: Fix 3-or-4 address byte mode logic

Flash chips that announce BFPT_DWORD1_ADDRESS_BYTES_3_OR_4 capability
get an addr_width of 3. This breaks when the flash chip is actually
larger than 16MB, since that requires a 4-byte address. The MX25L25635F
does exactly this, breaking anything over 16MB.

spi-nor only enables 4-byte opcodes or 4-byte address mode if addr_width
is 4, so no 4-byte mode is ever enabled. The > 16MB check in
spi_nor_set_addr_width() only works if addr_width wasn't already set
by the SFDP, which it was.

It could be fixed in a post_bfpt fixup for the MX25L25635F, but setting
addr_width to 4 when BFPT_DWORD1_ADDRESS_BYTES_3_OR_4 is found fixes the
problem for all such cases.

Signed-off-by: Bert Vermeulen <bert@...t.com>
---
 drivers/mtd/spi-nor/sfdp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index e2a43d39eb5f..6fedc425bcf7 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -456,10 +456,10 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
 	/* Number of address bytes. */
 	switch (bfpt.dwords[BFPT_DWORD(1)] & BFPT_DWORD1_ADDRESS_BYTES_MASK) {
 	case BFPT_DWORD1_ADDRESS_BYTES_3_ONLY:
-	case BFPT_DWORD1_ADDRESS_BYTES_3_OR_4:
 		nor->addr_width = 3;
 		break;

+	case BFPT_DWORD1_ADDRESS_BYTES_3_OR_4:
 	case BFPT_DWORD1_ADDRESS_BYTES_4_ONLY:
 		nor->addr_width = 4;
 		break;
-- 
2.17.1