linux-kernel - [PATCH] spi: spi-qpic-snand: document the limited bit error reporting capability

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Message-Id: <20250527-qpic-snand-limited-biterr-caps-v1-1-61f7cf87be1e@gmail.com>
Date: Tue, 27 May 2025 13:08:16 +0200
From: Gabor Juhos <j4g8y7@...il.com>
To: Mark Brown <broonie@...nel.org>, 
 Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Md Sadre Alam <quic_mdalam@...cinc.com>, 
 Varadarajan Narayanan <quic_varada@...cinc.com>, 
 Sricharan Ramabadhran <quic_srichara@...cinc.com>, 
 linux-spi@...r.kernel.org, linux-mtd@...ts.infradead.org, 
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Gabor Juhos <j4g8y7@...il.com>
Subject: [PATCH] spi: spi-qpic-snand: document the limited bit error
 reporting capability

The QPIC hardware is not capable of reporting the exact number of the
corrected bit errors, it only reports the number of the corrected bytes.

Document this behaviour in the code, and also issue a warning message
to inform the user about it.

No functional changes.

Signed-off-by: Gabor Juhos <j4g8y7@...il.com>
---
 drivers/spi/spi-qpic-snand.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/spi/spi-qpic-snand.c b/drivers/spi/spi-qpic-snand.c
index fd129650434f0129e24d3bdac7e7c4d5542627e6..c2f5ef899f6a60ad98b9d754b7cac1832d0500eb 100644
--- a/drivers/spi/spi-qpic-snand.c
+++ b/drivers/spi/spi-qpic-snand.c
@@ -639,6 +639,20 @@ static int qcom_spi_check_error(struct qcom_nand_controller *snandc)
 			unsigned int stat;
 
 			stat = buffer & BS_CORRECTABLE_ERR_MSK;
+
+			/*
+			 * The exact number of the corrected bits is
+			 * unknown because the hardware only reports the
+			 * number of the corrected bytes.
+			 *
+			 * Since we have no better solution at the moment,
+			 * report that value as the number of bit errors
+			 * despite that it is inaccurate in most cases.
+			 */
+			if (stat && stat != ecc_cfg->strength)
+				dev_warn_once(snandc->dev,
+					      "Warning: due to hw limitation, the reported number of the corrected bits may be inaccurate\n");
+
 			snandc->qspi->ecc_stats.corrected += stat;
 			max_bitflips = max(max_bitflips, stat);
 		}

---
base-commit: b00d6864a4c948529dc6ddd2df76bf175bf27c63
change-id: 20250527-qpic-snand-limited-biterr-caps-a198b01c1f0a

Best regards,
-- 
Gabor Juhos <j4g8y7@...il.com>