[PATCH net-next 0/4] net: dsa: ks8995: Post-move fixes

[PATCH net-next 0/4] net: dsa: ks8995: Post-move fixes

[Linus Walleij]

This fixes some glearing issues in the Micrel KS8995 driver
pointed out by Vladimir.

This patch series implements some required functionality
and strips the driver down to just KS8995 deeming the other
"micrel" variants to be actually handled by the Microchip
KSZ driver.

If the KS8995 should actually *also* be managed by the Microchip
driver and this driver deleted remains to be seen. It is clearly
the origin chip for that hardware: it is very close to the
"KSZ8 family" but there are differences.

It definitely has a different custom tag format for proper DSA
tagging, but I have implemented that: I now have to figure out
whether to do that on top of this driver or the KSZ driver before
continuing.

In the meantime, this patch series makes the situation better.

Signed-off-by: Linus Walleij <linusw@kernel.org>
---
Linus Walleij (4):
      net: dsa: ks8995: Add shutdown callback
      net: dsa: ks8955: Delete KSZ8864 and KSZ8795 support
      net: dsa: ks8995: Add stub bridge join/leave
      net: dsa: ks8995: Implement port isolation

 drivers/net/dsa/ks8995.c | 329 ++++++++++++++++++++++++++++-------------------
 1 file changed, 197 insertions(+), 132 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20260118-ks8995-fixups-84f25ac3f407

Best regards,
-- 
Linus Walleij <linusw@kernel.org>

[PATCH net-next 1/4] net: dsa: ks8995: Add shutdown callback

[Linus Walleij]

The DSA framework requires that dsa_switch_shutdown() be
called when the driver is shut down.

Fixes: a7fe8b266f65 ("net: dsa: ks8995: Add basic switch set-up")
Reported-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/dsa/ks8995.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/dsa/ks8995.c b/drivers/net/dsa/ks8995.c
index 77d8b842693c..ff01097601ec 100644
--- a/drivers/net/dsa/ks8995.c
+++ b/drivers/net/dsa/ks8995.c
@@ -838,6 +838,13 @@ static void ks8995_remove(struct spi_device *spi)
 	gpiod_set_value_cansleep(ks->reset_gpio, 1);
 }
 
+static void ks8995_shutdown(struct spi_device *spi)
+{
+	struct ks8995_switch *ks = spi_get_drvdata(spi);
+
+	dsa_switch_shutdown(ks->ds);
+}
+
 /* ------------------------------------------------------------------------ */
 static struct spi_driver ks8995_driver = {
 	.driver = {
@@ -846,6 +853,7 @@ static struct spi_driver ks8995_driver = {
 	},
 	.probe	  = ks8995_probe,
 	.remove	  = ks8995_remove,
+	.shutdown = ks8995_shutdown,
 	.id_table = ks8995_id,
 };
 

-- 
2.52.0

[PATCH net-next 2/4] net: dsa: ks8955: Delete KSZ8864 and KSZ8795 support

[Linus Walleij]

After studying the datasheets for a bit, I can conclude that
the register maps for the two KSZ variants explicitly said to
be supported by this driver are fully supported by the newer
Micrel KSZ driver, including full VLAN support and a different
custom tag than what the KS8995 is using.

Delete this support, users should be using the KSZ driver
CONFIG_NET_DSA_MICROCHIP_KSZ_SPI and any new device trees should
use:
micrel,ksz8864 -> microchip,ksz8864
micrel,ksz8795 -> microchip,ksz8795

Apparently Microchip acquired Micrel at some point and this
created the confusion.

Fixes: a7fe8b266f65 ("net: dsa: ks8995: Add basic switch set-up")
Reported-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/dsa/ks8995.c | 160 +++++++++--------------------------------------
 1 file changed, 28 insertions(+), 132 deletions(-)

diff --git a/drivers/net/dsa/ks8995.c b/drivers/net/dsa/ks8995.c
index ff01097601ec..5ad62fa4e52c 100644
--- a/drivers/net/dsa/ks8995.c
+++ b/drivers/net/dsa/ks8995.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * SPI driver for Micrel/Kendin KS8995M and KSZ8864RMN ethernet switches
+ * SPI driver for Micrel/Kendin KS8995M ethernet switch.
  *
  * Copyright (C) 2008 Gabor Juhos <juhosg at openwrt.org>
  * Copyright (C) 2025 Linus Walleij <linus.walleij@linaro.org>
@@ -114,11 +114,7 @@
 #define KS8995_REG_IAD1		0x76    /* Indirect Access Data 1 */
 #define KS8995_REG_IAD0		0x77    /* Indirect Access Data 0 */
 
-#define KSZ8864_REG_ID1		0xfe	/* Chip ID in bit 7 */
-
 #define KS8995_REGS_SIZE	0x80
-#define KSZ8864_REGS_SIZE	0x100
-#define KSZ8795_REGS_SIZE	0x100
 
 #define ID1_CHIPID_M		0xf
 #define ID1_CHIPID_S		4
@@ -127,11 +123,8 @@
 #define ID1_START_SW		1	/* start the switch */
 
 #define FAMILY_KS8995		0x95
-#define FAMILY_KSZ8795		0x87
 #define CHIPID_M		0
 #define KS8995_CHIP_ID		0x00
-#define KSZ8864_CHIP_ID		0x01
-#define KSZ8795_CHIP_ID		0x09
 
 #define KS8995_CMD_WRITE	0x02U
 #define KS8995_CMD_READ		0x03U
@@ -140,49 +133,6 @@
 #define KS8995_NUM_PORTS	5 /* 5 ports including the CPU port */
 #define KS8995_RESET_DELAY	10 /* usec */
 
-enum ks8995_chip_variant {
-	ks8995,
-	ksz8864,
-	ksz8795,
-	max_variant
-};
-
-struct ks8995_chip_params {
-	char *name;
-	int family_id;
-	int chip_id;
-	int regs_size;
-	int addr_width;
-	int addr_shift;
-};
-
-static const struct ks8995_chip_params ks8995_chip[] = {
-	[ks8995] = {
-		.name = "KS8995MA",
-		.family_id = FAMILY_KS8995,
-		.chip_id = KS8995_CHIP_ID,
-		.regs_size = KS8995_REGS_SIZE,
-		.addr_width = 8,
-		.addr_shift = 0,
-	},
-	[ksz8864] = {
-		.name = "KSZ8864RMN",
-		.family_id = FAMILY_KS8995,
-		.chip_id = KSZ8864_CHIP_ID,
-		.regs_size = KSZ8864_REGS_SIZE,
-		.addr_width = 8,
-		.addr_shift = 0,
-	},
-	[ksz8795] = {
-		.name = "KSZ8795CLX",
-		.family_id = FAMILY_KSZ8795,
-		.chip_id = KSZ8795_CHIP_ID,
-		.regs_size = KSZ8795_REGS_SIZE,
-		.addr_width = 12,
-		.addr_shift = 1,
-	},
-};
-
 struct ks8995_switch {
 	struct spi_device	*spi;
 	struct device		*dev;
@@ -190,23 +140,18 @@ struct ks8995_switch {
 	struct mutex		lock;
 	struct gpio_desc	*reset_gpio;
 	struct bin_attribute	regs_attr;
-	const struct ks8995_chip_params	*chip;
 	int			revision_id;
 	unsigned int max_mtu[KS8995_NUM_PORTS];
 };
 
 static const struct spi_device_id ks8995_id[] = {
-	{"ks8995", ks8995},
-	{"ksz8864", ksz8864},
-	{"ksz8795", ksz8795},
+	{"ks8995", 0},
 	{ }
 };
 MODULE_DEVICE_TABLE(spi, ks8995_id);
 
 static const struct of_device_id ks8995_spi_of_match[] = {
 	{ .compatible = "micrel,ks8995" },
-	{ .compatible = "micrel,ksz8864" },
-	{ .compatible = "micrel,ksz8795" },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, ks8995_spi_of_match);
@@ -237,10 +182,10 @@ static inline __be16 create_spi_cmd(struct ks8995_switch *ks, int cmd,
 {
 	u16 result = cmd;
 
-	/* make room for address (incl. address shift) */
-	result <<= ks->chip->addr_width + ks->chip->addr_shift;
+	/* make room for address */
+	result <<= 8;
 	/* add address */
-	result |= address << ks->chip->addr_shift;
+	result |= address;
 	/* SPI protocol needs big endian */
 	return cpu_to_be16(result);
 }
@@ -346,79 +291,37 @@ static int ks8995_reset(struct ks8995_switch *ks)
 static int ks8995_get_revision(struct ks8995_switch *ks)
 {
 	int err;
-	u8 id0, id1, ksz8864_id;
+	u8 id0, id1;
 
 	/* read family id */
 	err = ks8995_read_reg(ks, KS8995_REG_ID0, &id0);
-	if (err) {
-		err = -EIO;
-		goto err_out;
-	}
+	if (err)
+		return -EIO;
 
 	/* verify family id */
-	if (id0 != ks->chip->family_id) {
+	if (id0 != FAMILY_KS8995) {
 		dev_err(&ks->spi->dev, "chip family id mismatch: expected 0x%02x but 0x%02x read\n",
-			ks->chip->family_id, id0);
-		err = -ENODEV;
-		goto err_out;
+			FAMILY_KS8995, id0);
+		return -ENODEV;
 	}
 
-	switch (ks->chip->family_id) {
-	case FAMILY_KS8995:
-		/* try reading chip id at CHIP ID1 */
-		err = ks8995_read_reg(ks, KS8995_REG_ID1, &id1);
-		if (err) {
-			err = -EIO;
-			goto err_out;
-		}
-
-		/* verify chip id */
-		if ((get_chip_id(id1) == CHIPID_M) &&
-		    (get_chip_id(id1) == ks->chip->chip_id)) {
-			/* KS8995MA */
-			ks->revision_id = get_chip_rev(id1);
-		} else if (get_chip_id(id1) != CHIPID_M) {
-			/* KSZ8864RMN */
-			err = ks8995_read_reg(ks, KS8995_REG_ID1, &ksz8864_id);
-			if (err) {
-				err = -EIO;
-				goto err_out;
-			}
-
-			if ((ksz8864_id & 0x80) &&
-			    (ks->chip->chip_id == KSZ8864_CHIP_ID)) {
-				ks->revision_id = get_chip_rev(id1);
-			}
-
-		} else {
-			dev_err(&ks->spi->dev, "unsupported chip id for KS8995 family: 0x%02x\n",
-				id1);
-			err = -ENODEV;
-		}
-		break;
-	case FAMILY_KSZ8795:
-		/* try reading chip id at CHIP ID1 */
-		err = ks8995_read_reg(ks, KS8995_REG_ID1, &id1);
-		if (err) {
-			err = -EIO;
-			goto err_out;
-		}
+	/* try reading chip id at CHIP ID1 */
+	err = ks8995_read_reg(ks, KS8995_REG_ID1, &id1);
+	if (err)
+		return -EIO;
 
-		if (get_chip_id(id1) == ks->chip->chip_id) {
-			ks->revision_id = get_chip_rev(id1);
-		} else {
-			dev_err(&ks->spi->dev, "unsupported chip id for KSZ8795 family: 0x%02x\n",
-				id1);
-			err = -ENODEV;
-		}
-		break;
-	default:
-		dev_err(&ks->spi->dev, "unsupported family id: 0x%02x\n", id0);
-		err = -ENODEV;
-		break;
+	/* verify chip id */
+	if ((get_chip_id(id1) == CHIPID_M) &&
+	    (get_chip_id(id1) == KS8995_CHIP_ID)) {
+		/* KS8995MA */
+		ks->revision_id = get_chip_rev(id1);
+	} else {
+		dev_err(&ks->spi->dev, "unsupported chip id for KS8995 family: 0x%02x\n",
+			id1);
+		return -ENODEV;
 	}
-err_out:
-	return err;
+
+	return 0;
 }
 
 static int ks8995_check_config(struct ks8995_switch *ks)
@@ -747,12 +650,6 @@ static int ks8995_probe(struct spi_device *spi)
 {
 	struct ks8995_switch *ks;
 	int err;
-	int variant = spi_get_device_id(spi)->driver_data;
-
-	if (variant >= max_variant) {
-		dev_err(&spi->dev, "bad chip variant %d\n", variant);
-		return -ENODEV;
-	}
 
 	ks = devm_kzalloc(&spi->dev, sizeof(*ks), GFP_KERNEL);
 	if (!ks)
@@ -761,7 +658,6 @@ static int ks8995_probe(struct spi_device *spi)
 	mutex_init(&ks->lock);
 	ks->spi = spi;
 	ks->dev = &spi->dev;
-	ks->chip = &ks8995_chip[variant];
 
 	ks->reset_gpio = devm_gpiod_get_optional(&spi->dev, "reset",
 						 GPIOD_OUT_HIGH);
@@ -804,8 +700,8 @@ static int ks8995_probe(struct spi_device *spi)
 	if (err)
 		return err;
 
-	dev_info(&spi->dev, "%s device found, Chip ID:%x, Revision:%x\n",
-		 ks->chip->name, ks->chip->chip_id, ks->revision_id);
+	dev_info(&spi->dev, "KS8955MA device found, Chip ID:%x, Revision:%x\n",
+		 KS8995_CHIP_ID, ks->revision_id);
 
 	err = ks8995_check_config(ks);
 	if (err)

-- 
2.52.0

Re: [PATCH net-next 2/4] net: dsa: ks8955: Delete KSZ8864 and KSZ8795 support

[Simon Horman]

On Sun, Jan 18, 2026 at 11:07:32PM +0100, Linus Walleij wrote:

...

> @@ -346,79 +291,37 @@ static int ks8995_reset(struct ks8995_switch *ks)
>  static int ks8995_get_revision(struct ks8995_switch *ks)
>  {
>  	int err;
> -	u8 id0, id1, ksz8864_id;
> +	u8 id0, id1;
>  
>  	/* read family id */
>  	err = ks8995_read_reg(ks, KS8995_REG_ID0, &id0);
> -	if (err) {
> -		err = -EIO;
> -		goto err_out;
> -	}
> +	if (err)
> +		return -EIO;
>  
>  	/* verify family id */
> -	if (id0 != ks->chip->family_id) {
> +	if (id0 != FAMILY_KS8995) {
>  		dev_err(&ks->spi->dev, "chip family id mismatch: expected 0x%02x but 0x%02x read\n",
> -			ks->chip->family_id, id0);
> -		err = -ENODEV;
> -		goto err_out;
> +			FAMILY_KS8995, id0);
> +		return -ENODEV;
>  	}
>  
> -	switch (ks->chip->family_id) {
> -	case FAMILY_KS8995:
> -		/* try reading chip id at CHIP ID1 */
> -		err = ks8995_read_reg(ks, KS8995_REG_ID1, &id1);
> -		if (err) {
> -			err = -EIO;
> -			goto err_out;
> -		}
> -
> -		/* verify chip id */
> -		if ((get_chip_id(id1) == CHIPID_M) &&
> -		    (get_chip_id(id1) == ks->chip->chip_id)) {
> -			/* KS8995MA */
> -			ks->revision_id = get_chip_rev(id1);
> -		} else if (get_chip_id(id1) != CHIPID_M) {
> -			/* KSZ8864RMN */
> -			err = ks8995_read_reg(ks, KS8995_REG_ID1, &ksz8864_id);
> -			if (err) {
> -				err = -EIO;
> -				goto err_out;
> -			}
> -
> -			if ((ksz8864_id & 0x80) &&
> -			    (ks->chip->chip_id == KSZ8864_CHIP_ID)) {
> -				ks->revision_id = get_chip_rev(id1);
> -			}
> -
> -		} else {
> -			dev_err(&ks->spi->dev, "unsupported chip id for KS8995 family: 0x%02x\n",
> -				id1);
> -			err = -ENODEV;
> -		}
> -		break;
> -	case FAMILY_KSZ8795:
> -		/* try reading chip id at CHIP ID1 */
> -		err = ks8995_read_reg(ks, KS8995_REG_ID1, &id1);
> -		if (err) {
> -			err = -EIO;
> -			goto err_out;
> -		}
> +	/* try reading chip id at CHIP ID1 */
> +	err = ks8995_read_reg(ks, KS8995_REG_ID1, &id1);
> +	if (err)
> +		return -EIO;
>  
> -		if (get_chip_id(id1) == ks->chip->chip_id) {
> -			ks->revision_id = get_chip_rev(id1);
> -		} else {
> -			dev_err(&ks->spi->dev, "unsupported chip id for KSZ8795 family: 0x%02x\n",
> -				id1);
> -			err = -ENODEV;
> -		}
> -		break;
> -	default:
> -		dev_err(&ks->spi->dev, "unsupported family id: 0x%02x\n", id0);
> -		err = -ENODEV;
> -		break;
> +	/* verify chip id */
> +	if ((get_chip_id(id1) == CHIPID_M) &&
> +	    (get_chip_id(id1) == KS8995_CHIP_ID)) {

Hi Linus,

This seems a little odd to me.
The condition can be true, but only because the constants are equal (0).

What is the intention here?

Flagged by Smatch.

> +		/* KS8995MA */
> +		ks->revision_id = get_chip_rev(id1);
> +	} else {
> +		dev_err(&ks->spi->dev, "unsupported chip id for KS8995 family: 0x%02x\n",
> +			id1);
> +		return -ENODEV;
>  	}
> -err_out:
> -	return err;
> +
> +	return 0;
>  }

...

[PATCH net-next 3/4] net: dsa: ks8995: Add stub bridge join/leave

[Linus Walleij]

Implementing ks8995_port_pre_bridge_flags() and
ks8995_port_bridge_flags() without port_bridge_join()
is a no-op.

This adds stubs for bridge join/leave callbacks following
the pattern of drivers/net/dsa/microchip/ksz_common.c:
as we have STP callbacks and these will be called right
after bridge join/leave these will take care of the
job of setting up the learning which is all we support.

Fixes: a7fe8b266f65 ("net: dsa: ks8995: Add basic switch set-up")
Reported-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/dsa/ks8995.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/net/dsa/ks8995.c b/drivers/net/dsa/ks8995.c
index 5ad62fa4e52c..060bc8303a14 100644
--- a/drivers/net/dsa/ks8995.c
+++ b/drivers/net/dsa/ks8995.c
@@ -461,6 +461,26 @@ static void ks8995_port_disable(struct dsa_switch *ds, int port)
 	dev_dbg(ks->dev, "disable port %d\n", port);
 }
 
+static int ks8995_port_bridge_join(struct dsa_switch *ds, int port,
+				   struct dsa_bridge bridge,
+				   bool *tx_fwd_offload,
+				   struct netlink_ext_ack *extack)
+{
+	/* port_stp_state_set() will be called after to put the port in
+	 * appropriate state so there is no need to do anything.
+	 */
+
+	return 0;
+}
+
+static void ks8995_port_bridge_leave(struct dsa_switch *ds, int port,
+				     struct dsa_bridge bridge)
+{
+	/* port_stp_state_set() will be called after to put the port in
+	 * forwarding state so there is no need to do anything.
+	 */
+}
+
 static int ks8995_port_pre_bridge_flags(struct dsa_switch *ds, int port,
 					struct switchdev_brport_flags flags,
 					struct netlink_ext_ack *extack)
@@ -635,6 +655,8 @@ static int ks8995_get_max_mtu(struct dsa_switch *ds, int port)
 static const struct dsa_switch_ops ks8995_ds_ops = {
 	.get_tag_protocol = ks8995_get_tag_protocol,
 	.setup = ks8995_setup,
+	.port_bridge_join = ks8995_port_bridge_join,
+	.port_bridge_leave = ks8995_port_bridge_leave,
 	.port_pre_bridge_flags = ks8995_port_pre_bridge_flags,
 	.port_bridge_flags = ks8995_port_bridge_flags,
 	.port_enable = ks8995_port_enable,

-- 
2.52.0

[PATCH net-next 4/4] net: dsa: ks8995: Implement port isolation

[Linus Walleij]

It is unsound to not have proper port isolation on a
switch which supports it.

Set each port as isolated by default in the setup callback
and de-isolate and isolate the ports in the bridge join/leave
callbacks.

Fixes: a7fe8b266f65 ("net: dsa: ks8995: Add basic switch set-up")
Reported-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/dsa/ks8995.c | 143 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 141 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/ks8995.c b/drivers/net/dsa/ks8995.c
index 060bc8303a14..ad985f0d0dba 100644
--- a/drivers/net/dsa/ks8995.c
+++ b/drivers/net/dsa/ks8995.c
@@ -80,6 +80,11 @@
 #define KS8995_PC0_TAG_REM	BIT(1)	/* Enable tag removal on port */
 #define KS8995_PC0_PRIO_EN	BIT(0)	/* Enable priority handling */
 
+#define KS8995_PC1_SNIFF_PORT	BIT(7)	/* This port is a sniffer port */
+#define KS8995_PC1_RCV_SNIFF	BIT(6)	/* Packets received goes to sniffer port(s) */
+#define KS8995_PC1_XMIT_SNIFF	BIT(5)	/* Packets transmitted goes to sniffer port(s) */
+#define KS8995_PC1_PORT_VLAN	GENMASK(4, 0)	/* Port isolation mask */
+
 #define KS8995_PC2_TXEN		BIT(2)	/* Enable TX on port */
 #define KS8995_PC2_RXEN		BIT(1)	/* Enable RX on port */
 #define KS8995_PC2_LEARN_DIS	BIT(0)	/* Disable learning on port */
@@ -441,6 +446,44 @@ dsa_tag_protocol ks8995_get_tag_protocol(struct dsa_switch *ds,
 
 static int ks8995_setup(struct dsa_switch *ds)
 {
+	struct ks8995_switch *ks = ds->priv;
+	int ret;
+	u8 val;
+	int i;
+
+	/* Isolate all user ports so they can only send packets to itself and the CPU port */
+	for (i = 0; i < KS8995_CPU_PORT; i++) {
+		ret = ks8995_read_reg(ks, KS8995_REG_PC(i, KS8995_REG_PC1), &val);
+		if (ret) {
+			dev_err(ks->dev, "failed to read KS8995_REG_PC1 on port %d\n", i);
+			return ret;
+		}
+
+		val &= ~KS8995_PC1_PORT_VLAN;
+		val |= BIT(i) | BIT(KS8995_CPU_PORT);
+
+		ret = ks8995_write_reg(ks, KS8995_REG_PC(i, KS8995_REG_PC1), val);
+		if (ret) {
+			dev_err(ks->dev, "failed to write KS8995_REG_PC1 on port %d\n", i);
+			return ret;
+		}
+	}
+
+	/* The CPU port should be able to talk to all ports */
+	ret = ks8995_read_reg(ks, KS8995_REG_PC(KS8995_CPU_PORT, KS8995_REG_PC1), &val);
+	if (ret) {
+		dev_err(ks->dev, "failed to read KS8995_REG_PC1 on CPU port\n");
+		return ret;
+	}
+
+	val |= KS8995_PC1_PORT_VLAN;
+
+	ret = ks8995_write_reg(ks, KS8995_REG_PC(KS8995_CPU_PORT, KS8995_REG_PC1), val);
+	if (ret) {
+		dev_err(ks->dev, "failed to write KS8995_REG_PC1 on CPU port\n");
+		return ret;
+	}
+
 	return 0;
 }
 
@@ -466,8 +509,56 @@ static int ks8995_port_bridge_join(struct dsa_switch *ds, int port,
 				   bool *tx_fwd_offload,
 				   struct netlink_ext_ack *extack)
 {
+	struct ks8995_switch *ks = ds->priv;
+	unsigned int port_bitmap = 0;
+	int ret;
+	u8 val;
+	int i;
+
+	/* De-isolate this port from any other port on the bridge */
+	for (i = 0; i < KS8995_CPU_PORT; i++) {
+		/* Current port handled last */
+		if (i == port)
+			continue;
+		/* Not on this bridge */
+		if (!dsa_port_offloads_bridge(dsa_to_port(ds, i), &bridge))
+			continue;
+
+		ret = ks8995_read_reg(ks, KS8995_REG_PC(i, KS8995_REG_PC1), &val);
+		if (ret) {
+			dev_err(ks->dev, "failed to read KS8995_REG_PC1 on port %d\n", i);
+			return ret;
+		}
+
+		val |= BIT(port);
+
+		ret = ks8995_write_reg(ks, KS8995_REG_PC(i, KS8995_REG_PC1), val);
+		if (ret) {
+			dev_err(ks->dev, "failed to write KS8995_REG_PC1 on port %d\n", i);
+			return ret;
+		}
+
+		/* Accumulate this port for access by current */
+		port_bitmap |= BIT(i);
+	}
+
+	/* Let current port access all other ports on the bridge */
+	ret = ks8995_read_reg(ks, KS8995_REG_PC(port, KS8995_REG_PC1), &val);
+	if (ret) {
+		dev_err(ks->dev, "failed to read KS8995_REG_PC1 on port %d\n", port);
+		return ret;
+	}
+
+	val |= BIT(port_bitmap);
+
+	ret = ks8995_write_reg(ks, KS8995_REG_PC(port, KS8995_REG_PC1), val);
+	if (ret) {
+		dev_err(ks->dev, "failed to write KS8995_REG_PC1 on port %d\n", port);
+		return ret;
+	}
+
 	/* port_stp_state_set() will be called after to put the port in
-	 * appropriate state so there is no need to do anything.
+	 * appropriate state.
 	 */
 
 	return 0;
@@ -476,8 +567,56 @@ static int ks8995_port_bridge_join(struct dsa_switch *ds, int port,
 static void ks8995_port_bridge_leave(struct dsa_switch *ds, int port,
 				     struct dsa_bridge bridge)
 {
+	struct ks8995_switch *ks = ds->priv;
+	unsigned int port_bitmap = 0;
+	int ret;
+	u8 val;
+	int i;
+
+	/* Isolate this port from any other port on the bridge */
+	for (i = 0; i < KS8995_CPU_PORT; i++) {
+		/* Current port handled last */
+		if (i == port)
+			continue;
+		/* Not on this bridge */
+		if (!dsa_port_offloads_bridge(dsa_to_port(ds, i), &bridge))
+			continue;
+
+		ret = ks8995_read_reg(ks, KS8995_REG_PC(i, KS8995_REG_PC1), &val);
+		if (ret) {
+			dev_err(ks->dev, "failed to read KS8995_REG_PC1 on port %d\n", i);
+			return;
+		}
+
+		val &= ~BIT(port);
+
+		ret = ks8995_write_reg(ks, KS8995_REG_PC(i, KS8995_REG_PC1), val);
+		if (ret) {
+			dev_err(ks->dev, "failed to write KS8995_REG_PC1 on port %d\n", i);
+			return;
+		}
+
+		/* Accumulate this port for access by current */
+		port_bitmap |= BIT(i);
+	}
+
+	/* Isolate this port from all other ports formerly on the bridge */
+	ret = ks8995_read_reg(ks, KS8995_REG_PC(port, KS8995_REG_PC1), &val);
+	if (ret) {
+		dev_err(ks->dev, "failed to read KS8995_REG_PC1 on port %d\n", port);
+		return;
+	}
+
+	val &= ~BIT(port_bitmap);
+
+	ret = ks8995_write_reg(ks, KS8995_REG_PC(port, KS8995_REG_PC1), val);
+	if (ret) {
+		dev_err(ks->dev, "failed to write KS8995_REG_PC1 on port %d\n", port);
+		return;
+	}
+
 	/* port_stp_state_set() will be called after to put the port in
-	 * forwarding state so there is no need to do anything.
+	 * forwarding state.
 	 */
 }
 

-- 
2.52.0