linux-kernel - [PATCH 03/28] spi: spi-mem: Limit octal DTR constraints to octal DTR situations

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Message-Id: <20251031-winbond-v6-17-rc1-oddr-v1-3-be42de23ebf1@bootlin.com>
Date: Fri, 31 Oct 2025 18:26:47 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Mark Brown <broonie@...nel.org>, Richard Weinberger <richard@....at>, 
 Vignesh Raghavendra <vigneshr@...com>
Cc: Tudor Ambarus <tudor.ambarus@...aro.org>, 
 Pratyush Yadav <pratyush@...nel.org>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Steam Lin <STLin2@...bond.com>, Santhosh Kumar K <s-k6@...com>, 
 linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-mtd@...ts.infradead.org, Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH 03/28] spi: spi-mem: Limit octal DTR constraints to octal
 DTR situations

In this helper, any operation with a single DTR cycle (like 1S-1S-8D) is
considered requiring a duplicated command opcode. This is wrong as this
constraint only applies to octal DTR operations (8D-8D-8D).

Narrow the application of this constraint to the concerned bus
interface.

Note: none of the possible XD-XD-XD pattern, with X being one of {1, 2,
4} would benefit from this check either as there is only in octal DTR
mode that a single clock edge would be enough to transmit the full
opcode.

Make sure the constraint of expecting two bytes for the command is
applied to the relevant bus interface.

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 drivers/spi/spi-mem.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 064b99204d9ac4bc233307609defa4fbbaf4534a..71e3eaf59df97cf6d04e6e674810f12d037f384b 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -175,8 +175,19 @@ bool spi_mem_default_supports_op(struct spi_mem *mem,
 		if (op->data.swap16 && !spi_mem_controller_is_capable(ctlr, swap16))
 			return false;
 
-		if (op->cmd.nbytes != 2)
-			return false;
+		/* Extra 8D-8D-8D limitations */
+		if (op->cmd.dtr && op->cmd.buswidth == 8) {
+			if (op->cmd.nbytes != 2)
+				return false;
+
+			if ((op->addr.nbytes % 2) ||
+			    (op->dummy.nbytes % 2) ||
+			    (op->data.nbytes % 2)) {
+				dev_err(&ctlr->dev,
+					"Even byte numbers not allowed in octal DTR operations\n");
+				return false;
+			}
+		}
 	} else {
 		if (op->cmd.nbytes != 1)
 			return false;

-- 
2.51.0