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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Matthias Schiffer <matthias.schiffer@ew.tq-group.com>,
        Mark Brown <broonie@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 028/124] spi: cadence-quadspi: fix incorrect supports_op() return value
Date:   Tue, 26 Apr 2022 10:20:29 +0200
Message-Id: <20220426081748.104548213@linuxfoundation.org>
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From: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>

[ Upstream commit f1d388f216aeb41a5df518815ae559d14a6d438e ]

Since the conversion to spi-mem, the driver advertised support for
various operations that cqspi_set_protocol() was never expected to handle
correctly - in particuar all non-DTR operations with command or address
buswidth > 1. For DTR, all operations except for 8-8-8 would fail, as
cqspi_set_protocol() returns -EINVAL.

In non-DTR mode, this resulted in data corruption for SPI-NOR flashes that
support such operations. As a minimal fix that can be backported to stable
kernels, simply disallow the unsupported operations again to avoid this
issue.

Fixes: a314f6367787 ("mtd: spi-nor: Convert cadence-quadspi to use spi-mem framework")
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Link: https://lore.kernel.org/r/20220406132832.199777-1-matthias.schiffer@ew.tq-group.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/spi/spi-cadence-quadspi.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 1a6294a06e72..75680eecd2f7 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1226,9 +1226,24 @@ static bool cqspi_supports_mem_op(struct spi_mem *mem,
 	all_false = !op->cmd.dtr && !op->addr.dtr && !op->dummy.dtr &&
 		    !op->data.dtr;
 
-	/* Mixed DTR modes not supported. */
-	if (!(all_true || all_false))
+	if (all_true) {
+		/* Right now we only support 8-8-8 DTR mode. */
+		if (op->cmd.nbytes && op->cmd.buswidth != 8)
+			return false;
+		if (op->addr.nbytes && op->addr.buswidth != 8)
+			return false;
+		if (op->data.nbytes && op->data.buswidth != 8)
+			return false;
+	} else if (all_false) {
+		/* Only 1-1-X ops are supported without DTR */
+		if (op->cmd.nbytes && op->cmd.buswidth > 1)
+			return false;
+		if (op->addr.nbytes && op->addr.buswidth > 1)
+			return false;
+	} else {
+		/* Mixed DTR modes are not supported. */
 		return false;
+	}
 
 	if (all_true)
 		return spi_mem_dtr_supports_op(mem, op);
-- 
2.35.1