linux-kernel - [PATCH v7 2/7] mtd: spi-nor: ignore errors in spi_nor_unlock

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Date:   Thu,  3 Dec 2020 00:00:35 +0100
From:   Michael Walle <michael@...le.cc>
To:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Michael Walle <michael@...le.cc>
Subject: [PATCH v7 2/7] mtd: spi-nor: ignore errors in spi_nor_unlock_all()

Just try to unlock the whole SPI-NOR flash array. Don't abort the
probing in case of an error. Justifications:
 (1) For some boards, this just works because
     spi_nor_write_16bit_sr_and_check() is broken and just checks the
     second half of the 16bit. Once that will be fixed, SPI probe will
     fail for boards which has hardware-write protected SPI-NOR flashes.
 (2) Until now, hardware write-protection was the only viable solution
     to use the block protection bits. This is because this very
     function spi_nor_unlock_all() will be called unconditionally on
     every linux boot. Therefore, this bits only makes sense in
     combination with the hardware write-protection. If we would fail
     the SPI probe on an error in spi_nor_unlock_all() we'd break
     virtually all users of the block protection bits.
 (3) We should try hard to keep the MTD working even if the flash might
     not be writable/erasable.

Fixes: 3e0930f109e7 ("mtd: spi-nor: Rework the disabling of block write protection")
Signed-off-by: Michael Walle <michael@...le.cc>
---
changes since v6:
 - new patch

 drivers/mtd/spi-nor/core.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 5bee7c8da4dc..013198abe929 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -3121,20 +3121,27 @@ static int spi_nor_quad_enable(struct spi_nor *nor)
 }
 
 /**
- * spi_nor_unlock_all() - Unlocks the entire flash memory array.
+ * spi_nor_try_unlock_all() - Tries to unlock the entire flash memory array.
  * @nor:	pointer to a 'struct spi_nor'.
  *
  * Some SPI NOR flashes are write protected by default after a power-on reset
  * cycle, in order to avoid inadvertent writes during power-up. Backward
  * compatibility imposes to unlock the entire flash memory array at power-up
  * by default.
+ *
+ * Unprotecting the entire flash array will fail for boards which are hardware
+ * write-protected. Thus any errors are ignored.
  */
-static int spi_nor_unlock_all(struct spi_nor *nor)
+static void spi_nor_try_unlock_all(struct spi_nor *nor)
 {
-	if (nor->flags & SNOR_F_HAS_LOCK)
-		return spi_nor_unlock(&nor->mtd, 0, nor->params->size);
+	int ret;
 
-	return 0;
+	if (!(nor->flags & SNOR_F_HAS_LOCK))
+		return;
+
+	ret = spi_nor_unlock(&nor->mtd, 0, nor->params->size);
+	if (ret)
+		dev_dbg(nor->dev, "Failed to unlock the entire flash memory array\n");
 }
 
 static int spi_nor_init(struct spi_nor *nor)
@@ -3153,11 +3160,7 @@ static int spi_nor_init(struct spi_nor *nor)
 		return err;
 	}
 
-	err = spi_nor_unlock_all(nor);
-	if (err) {
-		dev_dbg(nor->dev, "Failed to unlock the entire flash memory array\n");
-		return err;
-	}
+	spi_nor_try_unlock_all(nor);
 
 	if (nor->addr_width == 4 &&
 	    nor->read_proto != SNOR_PROTO_8_8_8_DTR &&
-- 
2.20.1