[PATCH v3] mtd: spinand: Do not update the QE bit on devices without one

[Sagnik Sasmal]

Commit be0b86c648bf ("mtd: spinand: Gather all the bus interface
steps in one single function") moved quad-enable setup into
spinand_configure_chip(). The new code only determines whether quad
mode is needed when SPINAND_HAS_QE_BIT is set, but calls
spinand_init_quad_enable() unconditionally. This clears configuration
register bit 0 on devices without a QE bit.

That bit is not universally a QE bit. On the Winbond W25N02KV it is
H-DIS, which disables the active-low HOLD function. Clearing H-DIS
enables HOLD during single and dual I/O operations. If IO3 is not kept
high, the flash can pause a command and ignore clock and data.

H-DIS is not restored by the FFh reset command, allowing the incorrect
state to survive an SoC warm reboot while the flash remains powered.

Before the refactoring, spinand_init_quad_enable() returned without
touching the configuration register on devices without
SPINAND_HAS_QE_BIT. Restore that behavior by only calling the helper
when the flag is set.

Return zero explicitly once SSDR configuration completes, as all errors
are returned immediately. This avoids returning an uninitialized value
when neither optional configuration step runs.

The regression was reproduced on a JioRouter JIDU6401 with an MT7986
SoC and a W25N02KV. With Linux 6.18.44, sysupgrade failed and the
following warm reboot hung in BL2. With this change applied, both
sysupgrade and warm reboot completed successfully.

Fixes: be0b86c648bf ("mtd: spinand: Gather all the bus interface steps in one single function")
Cc: stable at vger.kernel.org
Suggested-by: Miquel Raynal <miquel.raynal at bootlin.com>
Assisted-by: LLM
Signed-off-by: Sagnik Sasmal <sagnik at sagnik.me>
---
Changes in v3:
- Return zero explicitly after successful SSDR configuration, avoiding an
  uninitialized return value on devices with neither SPINAND_HAS_QE_BIT
  nor a configure_chip callback, as reported by sashiko-bot.
- Compile-tested for arm64 with W=1.

Changes in v2:
- Call spinand_init_quad_enable() only inside the
  SPINAND_HAS_QE_BIT condition, as suggested by Miquel.
- Retested on a JioRouter JIDU6401; sysupgrade and the following warm
  reboot completed successfully.

 drivers/mtd/nand/spi/core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 43bbe2629..95353777d 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -1813,11 +1813,11 @@ static int spinand_configure_chip(struct spinand_device *spinand)
 		    spinand->ssdr_op_templates.write_cache->data.buswidth == 4 ||
 		    spinand->ssdr_op_templates.update_cache->data.buswidth == 4)
 			quad_enable = true;
-	}
 
-	ret = spinand_init_quad_enable(spinand, quad_enable);
-	if (ret)
-		return ret;
+		ret = spinand_init_quad_enable(spinand, quad_enable);
+		if (ret)
+			return ret;
+	}
 
 	if (spinand->configure_chip) {
 		ret = spinand->configure_chip(spinand, SSDR);
@@ -1825,7 +1825,7 @@ static int spinand_configure_chip(struct spinand_device *spinand)
 			return ret;
 	}
 
-	return ret;
+	return 0;
 }
 
 static int spinand_init_flash(struct spinand_device *spinand)
-- 
2.53.0