linux-kernel - [PATCH 3/4] drivers: mtd: spi-nand: repeat reading in regular mode if continuous reading fails

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Message-ID: <20250804192132.1406387-4-mikhail.kshevetskiy@iopsys.eu>
Date: Mon,  4 Aug 2025 22:21:31 +0300
From: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
To: Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Ray Liu <ray.liu@...oha.com>,
	Mark Brown <broonie@...nel.org>,
	Tudor Ambarus <tudor.ambarus@...aro.org>,
	Martin Kurbanov <mmkurbanov@...utedevices.com>,
	Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>,
	Cheng Ming Lin <chengminglin@...c.com.tw>,
	linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-spi@...r.kernel.org
Cc: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
Subject: [PATCH 3/4] drivers: mtd: spi-nand: repeat reading in regular mode if continuous reading fails

Continuous reading may result in multiple flash pages reading in one
operation. Unfortunately, not all spi-nand controllers support such
large reading. They will read less data. Unfortunately, the operation
can't be continued.

In this case:
 * disable continuous reading on this (not good enough) spi controller
 * repeat reading in regular mode.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
---
 drivers/mtd/nand/spi/core.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index ff6a1e2fcfdc..88e4c00cccc4 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -431,7 +431,7 @@ static int spinand_read_from_cache_op(struct spinand_device *spinand,
 		 * Toggling the CS during a continuous read is forbidden.
 		 */
 		if (nbytes && req->continuous)
-			return -EIO;
+			return -E2BIG;
 	}
 
 	if (req->datalen)
@@ -893,15 +893,26 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 	struct spinand_device *spinand = mtd_to_spinand(mtd);
 	struct mtd_ecc_stats old_stats;
 	unsigned int max_bitflips = 0;
-	int ret;
+	int ret = -E2BIG;
 
 	mutex_lock(&spinand->lock);
 
 	old_stats = mtd->ecc_stats;
 
-	if (spinand_use_cont_read(mtd, from, ops))
+	if (spinand_use_cont_read(mtd, from, ops)) {
 		ret = spinand_mtd_continuous_page_read(mtd, from, ops, &max_bitflips);
-	else
+		if (ret == -E2BIG) {
+			/*
+			 * Some spi controllers may not support reading up to
+			 * erase block size. They will read less data than
+			 * expected. If this happen disable continuous mode
+			 * and repeat reading in normal mode.
+			 */
+			spinand->cont_read_possible = false;
+		}
+	}
+
+	if (ret == -E2BIG)
 		ret = spinand_mtd_regular_page_read(mtd, from, ops, &max_bitflips);
 
 	if (ops->stats) {
-- 
2.47.2