linux-kernel - [PATCH net] net: dsa: microchip: Select SPI

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Message-Id: <20250910-fix-omap-spi-v1-1-fd732c42b7be@bootlin.com>
Date: Wed, 10 Sep 2025 15:07:21 +0200
From: Bastien Curutchet <bastien.curutchet@...tlin.com>
To: Woojung Huh <woojung.huh@...rochip.com>, UNGLinuxDriver@...rochip.com, 
 Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Tristram Ha <tristram.ha@...rochip.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Miquèl Raynal <miquel.raynal@...tlin.com>, 
 Pascal Eberhard <pascal.eberhard@...com>, netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 "Bastien Curutchet (Schneider Electric)" <bastien.curutchet@...tlin.com>
Subject: [PATCH net] net: dsa: microchip: Select SPI_MODE 0 for KSZ8463

KSZ8463 expects the SPI clock to be low on idle and samples data on
rising edges. This fits SPI mode 0 (CPOL = 0 / CPHA = 0) but the SPI
mode is set to 3 for all the switches supported by the driver. This
can lead to invalid read/write on the SPI bus.

Set SPI mode to 0 for the KSZ8463.
Leave SPI mode 3 as default for the other switches.

Signed-off-by: Bastien Curutchet (Schneider Electric) <bastien.curutchet@...tlin.com>
Fixes: 84c47bfc5b3b ("net: dsa: microchip: Add KSZ8463 switch support to KSZ DSA driver")
---
 drivers/net/dsa/microchip/ksz_spi.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/microchip/ksz_spi.c b/drivers/net/dsa/microchip/ksz_spi.c
index d8001734b05741446fa78a1e88c2f82e894835ce..dcc0dbddf7b9d70fbfb31d4b260b80ca78a65975 100644
--- a/drivers/net/dsa/microchip/ksz_spi.c
+++ b/drivers/net/dsa/microchip/ksz_spi.c
@@ -139,6 +139,7 @@ static int ksz_spi_probe(struct spi_device *spi)
 	const struct regmap_config *regmap_config;
 	const struct ksz_chip_data *chip;
 	struct device *ddev = &spi->dev;
+	u32 spi_mode = SPI_MODE_3;
 	struct regmap_config rc;
 	struct ksz_device *dev;
 	int i, ret = 0;
@@ -155,8 +156,10 @@ static int ksz_spi_probe(struct spi_device *spi)
 	dev->chip_id = chip->chip_id;
 	if (chip->chip_id == KSZ88X3_CHIP_ID)
 		regmap_config = ksz8863_regmap_config;
-	else if (chip->chip_id == KSZ8463_CHIP_ID)
+	else if (chip->chip_id == KSZ8463_CHIP_ID) {
 		regmap_config = ksz8463_regmap_config;
+		spi_mode = SPI_MODE_0;
+	}
 	else if (chip->chip_id == KSZ8795_CHIP_ID ||
 		 chip->chip_id == KSZ8794_CHIP_ID ||
 		 chip->chip_id == KSZ8765_CHIP_ID)
@@ -185,7 +188,7 @@ static int ksz_spi_probe(struct spi_device *spi)
 		dev->pdata = spi->dev.platform_data;

 	/* setup spi */
-	spi->mode = SPI_MODE_3;
+	spi->mode = spi_mode;
 	ret = spi_setup(spi);
 	if (ret)
 		return ret;

---
base-commit: c65e2aee8971eb9d4bc2b8edc3a3a62dc98f0410
change-id: 20250910-fix-omap-spi-d7c64f2416df

Best regards,
-- 
Bastien Curutchet <bastien.curutchet@...tlin.com>