RE: [PATCH net-next v1 5/9] net: dsa: microchip: add support for different DCB app configurations

[Naveen Mamindlapalli <naveenm@marvell.com>]

> -----Original Message-----
> From: Oleksij Rempel <o.rempel@pengutronix.de>
> Sent: Thursday, March 28, 2024 9:35 PM
> To: David S. Miller <davem@davemloft.net>; Andrew Lunn <andrew@lunn.ch>;
> Eric Dumazet <edumazet@google.com>; Florian Fainelli <f.fainelli@gmail.com>;
> Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; Vladimir
> Oltean <olteanv@gmail.com>; Woojung Huh <woojung.huh@microchip.com>;
> Arun Ramadoss <arun.ramadoss@microchip.com>
> Cc: Oleksij Rempel <o.rempel@pengutronix.de>; kernel@pengutronix.de; linux-
> kernel@vger.kernel.org; netdev@vger.kernel.org;
> UNGLinuxDriver@microchip.com; David Ahern <dsahern@kernel.org>; Simon
> Horman <horms@kernel.org>; Willem de Bruijn <willemb@google.com>; Søren
> Andersen <san@skov.dk>
> Subject: [PATCH net-next v1 5/9] net: dsa: microchip: add support
> for different DCB app configurations
> 
> Add DCB support to configure app trust sources and default port priority.
> 
> Following commands can be used for testing:
> dcb apptrust set dev lan1 order pcp dscp dcb app replace dev lan1 default-prio 3
> 
> Since it is not possible to configure DSCP-Prio mapping per port, this patch
> provide only ability to read switch global dscp-prio mapping and way to
> enable/disable app trust for DSCP.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  drivers/net/dsa/microchip/Kconfig      |   2 +
>  drivers/net/dsa/microchip/Makefile     |   2 +-
>  drivers/net/dsa/microchip/ksz_common.c |  12 +-
>  drivers/net/dsa/microchip/ksz_common.h |   5 +
>  drivers/net/dsa/microchip/ksz_dcb.c    | 533 +++++++++++++++++++++++++
>  drivers/net/dsa/microchip/ksz_dcb.h    |  21 +
>  6 files changed, 573 insertions(+), 2 deletions(-)  create mode 100644
> drivers/net/dsa/microchip/ksz_dcb.c
>  create mode 100644 drivers/net/dsa/microchip/ksz_dcb.h
> 
> diff --git a/drivers/net/dsa/microchip/Kconfig b/drivers/net/dsa/microchip/Kconfig
> index 394ca8678d2ba..c1b906c05a025 100644
> --- a/drivers/net/dsa/microchip/Kconfig
> +++ b/drivers/net/dsa/microchip/Kconfig
> @@ -4,6 +4,8 @@ menuconfig NET_DSA_MICROCHIP_KSZ_COMMON
>  	depends on NET_DSA
>  	select NET_DSA_TAG_KSZ
>  	select NET_DSA_TAG_NONE
> +	select NET_IEEE8021Q_HELPERS
> +	select DCB
>  	help
>  	  This driver adds support for Microchip KSZ9477 series switch and
>  	  KSZ8795/KSZ88x3 switch chips.
> diff --git a/drivers/net/dsa/microchip/Makefile b/drivers/net/dsa/microchip/Makefile
> index 49459a50dbc81..1cfba1ec9355a 100644
> --- a/drivers/net/dsa/microchip/Makefile
> +++ b/drivers/net/dsa/microchip/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ_COMMON)	+= ksz_switch.o
> -ksz_switch-objs := ksz_common.o
> +ksz_switch-objs := ksz_common.o ksz_dcb.o
>  ksz_switch-objs += ksz9477.o ksz9477_acl.o ksz9477_tc_flower.o  ksz_switch-
> objs += ksz8795.o  ksz_switch-objs += lan937x_main.o diff --git
> a/drivers/net/dsa/microchip/ksz_common.c
> b/drivers/net/dsa/microchip/ksz_common.c
> index cf81739d91dae..ea2d6f8d381bc 100644
> --- a/drivers/net/dsa/microchip/ksz_common.c
> +++ b/drivers/net/dsa/microchip/ksz_common.c
> @@ -28,6 +28,7 @@
>  #include <net/switchdev.h>
> 
>  #include "ksz_common.h"
> +#include "ksz_dcb.h"
>  #include "ksz_ptp.h"
>  #include "ksz8.h"
>  #include "ksz9477.h"
> @@ -2371,6 +2372,10 @@ static int ksz_setup(struct dsa_switch *ds)
>  		goto out_ptp_clock_unregister;
>  	}
> 
> +	ret = ksz_dcb_init(dev);
> +	if (ret)
> +		goto out_ptp_clock_unregister;
> +
>  	/* start switch */
>  	regmap_update_bits(ksz_regmap_8(dev), regs[S_START_CTRL],
>  			   SW_START, SW_START);
> @@ -2698,7 +2703,7 @@ static int ksz_port_setup(struct dsa_switch *ds, int
> port)
>  	 * there is no need to do anything.
>  	 */
> 
> -	return 0;
> +	return ksz_dcb_init_port(dev, port);
>  }
> 
>  void ksz_port_stp_state_set(struct dsa_switch *ds, int port, u8 state) @@ -
> 3950,6 +3955,11 @@ static const struct dsa_switch_ops ksz_switch_ops = {
>  	.port_setup_tc		= ksz_setup_tc,
>  	.get_mac_eee		= ksz_get_mac_eee,
>  	.set_mac_eee		= ksz_set_mac_eee,
> +	.port_get_default_prio	= ksz_port_get_default_prio,
> +	.port_set_default_prio	= ksz_port_set_default_prio,
> +	.port_get_dscp_prio	= ksz_port_get_dscp_prio,
> +	.port_set_apptrust	= ksz_port_set_apptrust,
> +	.port_get_apptrust	= ksz_port_get_apptrust,
>  };
> 
>  struct ksz_device *ksz_switch_alloc(struct device *base, void *priv) diff --git
> a/drivers/net/dsa/microchip/ksz_common.h
> b/drivers/net/dsa/microchip/ksz_common.h
> index 1bedd240cbbe4..4f48a8347e5de 100644
> --- a/drivers/net/dsa/microchip/ksz_common.h
> +++ b/drivers/net/dsa/microchip/ksz_common.h
> @@ -621,6 +621,11 @@ static inline bool ksz_is_ksz88x3(struct ksz_device
> *dev)
>  	return dev->chip_id == KSZ8830_CHIP_ID;  }
> 
> +static inline bool is_ksz8(struct ksz_device *dev) {
> +	return ksz_is_ksz87xx(dev) || ksz_is_ksz88x3(dev); }
> +
>  static inline int is_lan937x(struct ksz_device *dev)  {
>  	return dev->chip_id == LAN9370_CHIP_ID || diff --git
> a/drivers/net/dsa/microchip/ksz_dcb.c b/drivers/net/dsa/microchip/ksz_dcb.c
> new file mode 100644
> index 0000000000000..527bf10d35dd3
> --- /dev/null
> +++ b/drivers/net/dsa/microchip/ksz_dcb.c
> @@ -0,0 +1,533 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2024 Pengutronix, Oleksij Rempel
> +<kernel@pengutronix.de>
> +
> +#include <linux/dsa/ksz_common.h>
> +#include <net/dsa.h>
> +#include <net/dscp.h>
> +#include <net/ieee8021q.h>
> +
> +#include "ksz_common.h"
> +#include "ksz_dcb.h"
> +#include "ksz8.h"
> +
> +#define KSZ8_REG_PORT_1_CTRL_0			0x10
> +#define KSZ8_PORT_DIFFSERV_ENABLE		BIT(6)
> +#define KSZ8_PORT_802_1P_ENABLE			BIT(5)
> +#define KSZ8_PORT_BASED_PRIO_M			GENMASK(4, 3)
> +
> +#define KSZ88X3_REG_TOS_DSCP_CTRL		0x60
> +#define KSZ8765_REG_TOS_DSCP_CTRL		0x90
> +
> +#define KSZ9477_REG_SW_MAC_TOS_CTRL		0x033e
> +#define KSZ9477_SW_TOS_DSCP_REMAP		BIT(0)
> +#define KSZ9477_SW_TOS_DSCP_DEFAULT_PRIO_M	GENMASK(5, 3)
> +
> +#define KSZ9477_REG_DIFFSERV_PRIO_MAP		0x0340
> +
> +#define KSZ9477_REG_PORT_MRI_PRIO_CTRL		0x0801
> +#define KSZ9477_PORT_HIGHEST_PRIO		BIT(7)
> +#define KSZ9477_PORT_OR_PRIO			BIT(6)
> +#define KSZ9477_PORT_MAC_PRIO_ENABLE		BIT(4)
> +#define KSZ9477_PORT_VLAN_PRIO_ENABLE		BIT(3)
> +#define KSZ9477_PORT_802_1P_PRIO_ENABLE		BIT(2)
> +#define KSZ9477_PORT_DIFFSERV_PRIO_ENABLE	BIT(1)
> +#define KSZ9477_PORT_ACL_PRIO_ENABLE		BIT(0)
> +
> +#define KSZ9477_REG_PORT_MRI_MAC_CTRL		0x0802
> +#define KSZ9477_PORT_BASED_PRIO_M		GENMASK(2, 0)
> +
> +struct ksz_apptrust_map {
> +	u8 apptrust;
> +	u8 bit;
> +};
> +
> +static const struct ksz_apptrust_map ksz8_apptrust_map_to_bit[] = {
> +	{ DCB_APP_SEL_PCP, KSZ8_PORT_802_1P_ENABLE },
> +	{ IEEE_8021QAZ_APP_SEL_DSCP, KSZ8_PORT_DIFFSERV_ENABLE },
> };
> +
> +static const struct ksz_apptrust_map ksz9477_apptrust_map_to_bit[] = {
> +	{ DCB_APP_SEL_PCP, KSZ9477_PORT_802_1P_PRIO_ENABLE },
> +	{ IEEE_8021QAZ_APP_SEL_DSCP,
> KSZ9477_PORT_DIFFSERV_PRIO_ENABLE }, };
> +
> +/**
> + * ksz_supported_apptrust[] - Supported apptrust selectors and Priority Order
> + *			      of Internal Priority Value (IPV) sources.
> + *
> + * This array defines the apptrust selectors supported by the hardware,
> +where
> + * the index within the array indicates the priority of the selector -
> +lower
> + * indices correspond to higher priority. This fixed priority scheme is
> +due to
> + * the hardware's design, which does not support configurable priority
> +among
> + * different priority sources.
> + *
> + * The priority sources, including Tail Tag, ACL, VLAN PCP and DSCP are
> +ordered
> + * by the hardware's fixed logic, as detailed below. The order reflects
> +a
> + * non-configurable precedence where certain types of priority
> +information
> + * override others:
> + *
> + * 1. Tail Tag - Highest priority, overrides ACL, VLAN PCP, and DSCP priorities.
> + * 2. ACL - Overrides VLAN PCP and DSCP priorities.
> + * 3. VLAN PCP - Overrides DSCP priority.
> + * 4. DSCP - Lowest priority, does not override any other priority source.
> + *
> + * In this context, the array's lower index (higher priority) for
> + * 'DCB_APP_SEL_PCP' suggests its relative priority over
> + * 'IEEE_8021QAZ_APP_SEL_DSCP' within the system's fixed priority scheme.
> + *
> + * DCB_APP_SEL_PCP - Priority Code Point selector
> + * IEEE_8021QAZ_APP_SEL_DSCP - Differentiated Services Code Point
> +selector  */ static const u8 ksz_supported_apptrust[] = {
> +	DCB_APP_SEL_PCP,
> +	IEEE_8021QAZ_APP_SEL_DSCP,
> +};
> +
> +static const u8 ksz8_port2_supported_apptrust[] = {
> +	DCB_APP_SEL_PCP,
> +};
> +
> +static const char * const ksz_supported_apptrust_variants[] = {
> +	"empty", "dscp", "pcp", "dscp pcp"
> +};
> +
> +static void ksz_get_defult_port_prio_reg(struct ksz_device *dev, int *reg,
> +					 u8 *mask, int *shift)
> +{
> +	if (is_ksz8(dev)) {
> +		*reg = KSZ8_REG_PORT_1_CTRL_0;
> +		*mask = KSZ8_PORT_BASED_PRIO_M;
> +		*shift = __bf_shf(KSZ8_PORT_BASED_PRIO_M);
> +	} else {
> +		*reg = KSZ9477_REG_PORT_MRI_MAC_CTRL;
> +		*mask = KSZ9477_PORT_BASED_PRIO_M;
> +		*shift = __bf_shf(KSZ9477_PORT_BASED_PRIO_M);
> +	}
> +}
> +
> +/**
> + * ksz_port_get_default_prio - Retrieves the default priority for a port on a
> + *			       KSZ switch
> + * @ds: Pointer to the DSA switch structure
> + * @port: Port number from which to get the default priority
> + *
> + * This function fetches the default priority for the specified port on
> +a KSZ
> + * switch.
> + *
> + * Return: The default priority of the port on success, or a negative
> +error
> + * code on failure.
> + */
> +int ksz_port_get_default_prio(struct dsa_switch *ds, int port) {
> +	struct ksz_device *dev = ds->priv;
> +	int ret, reg, shift;
> +	u8 data, mask;
> +
> +	ksz_get_defult_port_prio_reg(dev, &reg, &mask, &shift);
> +
> +	ret = ksz_pread8(dev, port, reg, &data);
> +	if (ret)
> +		return ret;
> +
> +	return (data & mask) >> shift;
> +}
> +
> +/**
> + * ksz_port_set_default_prio - Sets the default priority for a port on a KSZ
> + *			       switch
> + * @ds: Pointer to the DSA switch structure
> + * @port: Port number for which to set the default priority
> + * @prio: Priority value to set
> + *
> + * This function sets the default priority for the specified port on a
> +KSZ
> + * switch.
> + *
> + * Return: 0 on success, or a negative error code on failure.
> + */
> +int ksz_port_set_default_prio(struct dsa_switch *ds, int port, u8 prio)
> +{
> +	struct ksz_device *dev = ds->priv;
> +	int reg, shift;
> +	u8 mask;
> +
> +	if (prio >= dev->info->num_tx_queues)
> +		return -EINVAL;
> +
> +	ksz_get_defult_port_prio_reg(dev, &reg, &mask, &shift);
> +
> +	return ksz_prmw8(dev, port, reg, mask, (prio << shift) & mask); }
> +
> +/**
> + * ksz_get_dscp_prio_reg - Retrieves the DSCP-to-priority-mapping
> +register
> + * @dev: Pointer to the KSZ switch device structure
> + * @reg: Pointer to the register address to be set
> + * @per_reg: Pointer to the number of DSCP values per register
> + * @mask: Pointer to the mask to be set
> + *
> + * This function retrieves the DSCP to priority mapping register, the
> +number of
> + * DSCP values per register, and the mask to be set.
> + */
> +static void ksz_get_dscp_prio_reg(struct ksz_device *dev, int *reg,
> +				  int *per_reg, u8 *mask)
> +{
> +	if (ksz_is_ksz87xx(dev)) {
> +		*reg = KSZ8765_REG_TOS_DSCP_CTRL;
> +		*per_reg = 4;
> +		*mask = GENMASK(1, 0);
> +	} else if (ksz_is_ksz88x3(dev)) {
> +		*reg = KSZ88X3_REG_TOS_DSCP_CTRL;
> +		*per_reg = 4;
> +		*mask = GENMASK(1, 0);
> +	} else {
> +		*reg = KSZ9477_REG_DIFFSERV_PRIO_MAP;
> +		*per_reg = 2;
> +		*mask = GENMASK(2, 0);
> +	}
> +}
> +
> +/**
> + * ksz_port_get_dscp_prio - Retrieves the priority for a DSCP value on a KSZ
> + *			    switch
> + * @ds: Pointer to the DSA switch structure
> + * @port: Port number for which to get the priority
> + * @dscp: DSCP value for which to get the priority
> + *
> + * This function fetches the priority value from switch global
> +DSCP-to-priorty
> + * mapping table for the specified DSCP value.
> + *
> + * Return: The priority value for the DSCP on success, or a negative
> +error
> + * code on failure.
> + */
> +int ksz_port_get_dscp_prio(struct dsa_switch *ds, int port, u8 dscp) {
> +	struct ksz_device *dev = ds->priv;
> +	int reg, per_reg, ret, shift;
> +	u8 data, mask;
> +
> +	ksz_get_dscp_prio_reg(dev, &reg, &per_reg, &mask);
> +
> +	/* If DSCP remapping is disabled, DSCP bits 3-5 are used as Internal
> +	 * Priority Value (IPV)
> +	 */
> +	if (!is_ksz8(dev)) {
> +		ret = ksz_read8(dev, KSZ9477_REG_SW_MAC_TOS_CTRL,
> &data);
> +		if (ret)
> +			return ret;
> +
> +		/* If DSCP remapping is disabled, DSCP bits 3-5 are used as
> +		 * Internal Priority Value (IPV)
> +		 */
> +		if (!(data & KSZ9477_SW_TOS_DSCP_REMAP))
> +			return
> FIELD_GET(KSZ9477_SW_TOS_DSCP_DEFAULT_PRIO_M,
> +					 dscp);
> +	}
> +
> +	/* In case DSCP remapping is enabled, we need to write the DSCP to
> +	 * priority mapping table.
> +	 */
> +	reg += dscp / per_reg;
> +	ret = ksz_read8(dev, reg, &data);
> +	if (ret)
> +		return ret;
> +
> +	shift = (dscp % per_reg) * (8 / per_reg);
> +
> +	return (data >> shift) & mask;
> +}
> +
> +/**
> + * ksz_init_global_dscp_map - Initializes the global DSCP-to-priority
> +mapping
> + * @dev: Pointer to the KSZ switch device structure
> + *
> + * This function initializes the global DSCP-to-priority mapping table
> +for the
> + * switch.
> + *
> + * Return: 0 on success, or a negative error code on failure  */ static
> +int ksz_init_global_dscp_map(struct ksz_device *dev) {
> +	int reg, per_reg, ret, dscp;
> +	u8 data = 0;
> +	u8 mask;
> +
> +	/* On KSZ9xxx variants, DSCP remapping is disabled by default.
> +	 * Enable to have, predictable and reproducible behavior across
> +	 * different devices.
> +	 */
> +	if (!is_ksz8(dev)) {
> +		ret = ksz_rmw8(dev, KSZ9477_REG_SW_MAC_TOS_CTRL,
> +			       KSZ9477_SW_TOS_DSCP_REMAP,
> +			       KSZ9477_SW_TOS_DSCP_REMAP);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ksz_get_dscp_prio_reg(dev, &reg, &per_reg, &mask);
> +
> +	for (dscp = 0; dscp < DSCP_MAX; dscp++) {
> +		int ipv, shift;
> +
> +		/* Map DSCP to Traffic Type, which is corresponding to the
> +		 * Internal Priority Value (IPV) in the switch.
> +		 */
> +		if (!is_ksz8(dev)) {
> +			ipv = ietf_dscp_to_ieee8021q_tt(dscp);
> +		} else {
> +			ipv =
> ieee8021q_tt_to_tc(ietf_dscp_to_ieee8021q_tt(dscp),
> +						 dev->info->num_tx_queues);
> +		}

No need for braces for single statement.

> +		shift = (dscp % per_reg) * (8 / per_reg);
> +		data |= (ipv & mask) << shift;
> +
> +		if (dscp % per_reg == per_reg - 1) {
> +			ret = ksz_write8(dev, reg + (dscp / per_reg), data);
> +			if (ret)
> +				return ret;
> +
> +			data = 0;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * ksz_apptrust_error - Prints an error message for an invalid apptrust
> +selector
> + * @dev: Pointer to the KSZ switch device structure
> + *
> + * This function prints an error message when an invalid apptrust
> +selector is
> + * provided.
> + */
> +static void ksz_apptrust_error(struct ksz_device *dev) {
> +	char supported_apptrust_variants[64];
> +	int i;
> +
> +	supported_apptrust_variants[0] = '\0';
> +	for (i = 0; i < ARRAY_SIZE(ksz_supported_apptrust_variants); i++) {
> +		if (i > 0)
> +			strlcat(supported_apptrust_variants, ", ",
> +				sizeof(supported_apptrust_variants));
> +		strlcat(supported_apptrust_variants,
> +			ksz_supported_apptrust_variants[i],
> +			sizeof(supported_apptrust_variants));
> +	}
> +
> +	dev_err(dev->dev, "Invalid apptrust selector or priority order. Supported:
> %s\n",
> +		supported_apptrust_variants);
> +}
> +
> +/**
> + * ksz_port_set_apptrust_validate - Validates the apptrust selectors
> + * @dev: Pointer to the KSZ switch device structure
> + * @port: Port number for which to set the apptrust selectors
> + * @sel: Array of apptrust selectors to validate
> + * @nsel: Number of apptrust selectors in the array
> + *
> + * This function validates the apptrust selectors provided and ensures
> +that
> + * they are in the correct order.
> + *
> + * This family of switches supports two apptrust selectors:
> +DCB_APP_SEL_PCP and
> + * IEEE_8021QAZ_APP_SEL_DSCP. The priority order of the selectors is
> +fixed and
> + * cannot be changed. The order is as follows:
> + * 1. DCB_APP_SEL_PCP - Priority Code Point selector (highest priority)
> + * 2. IEEE_8021QAZ_APP_SEL_DSCP - Differentiated Services Code Point
> selector
> + *   (lowest priority)
> + *
> + * Return: 0 on success, or a negative error code on failure  */ static
> +int ksz_port_set_apptrust_validate(struct ksz_device *dev, int port,
> +					  const u8 *sel, int nsel)
> +{
> +	int i, j, j_prev, found;
> +
> +	/* Iterate through the requested selectors */
> +	for (i = 0; i < nsel; i++) {
> +		found = 0;
> +
> +		/* Check if the current selector is supported by the hardware */
> +		for (j = 0; j < sizeof(ksz_supported_apptrust); j++) {
> +			if (sel[i] != ksz_supported_apptrust[j])
> +				continue;
> +
> +			found = 1;
> +
> +			/* Ensure that no higher priority selector (lower index)
> +			 * precedes a lower priority one
> +			 */
> +			if (i > 0 && j <= j_prev)

j_prev is uninitialized. It may contain garbage value.

> +				goto invalid;
> +
> +			j_prev = j;
> +			break;
> +		}
> +
> +		if (!found)
> +			goto invalid;
> +	}
> +
> +	return 0;
> +
> +invalid:
> +	ksz_apptrust_error(dev);
> +
> +	return -EINVAL;
> +}
> +
> +/**
> + * ksz_get_apptrus_map_and_reg - Retrieves the apptrust map and
> +register
> + * @dev: Pointer to the KSZ switch device structure
> + * @map: Pointer to the apptrust map to be set
> + * @reg: Pointer to the register address to be set
> + * @mask: Pointer to the mask to be set
> + *
> + * This function retrieves the apptrust map and register address for
> +the
> + * apptrust configuration.
> + */
> +static void ksz_get_apptrus_map_and_reg(struct ksz_device *dev,
> +					const struct ksz_apptrust_map **map,
> +					int *reg, u8 *mask)
> +{
> +	if (is_ksz8(dev)) {
> +		*map = ksz8_apptrust_map_to_bit;
> +		*reg = KSZ8_REG_PORT_1_CTRL_0;
> +		*mask = KSZ8_PORT_DIFFSERV_ENABLE |
> KSZ8_PORT_802_1P_ENABLE;
> +	} else {
> +		*map = ksz9477_apptrust_map_to_bit;
> +		*reg = KSZ9477_REG_PORT_MRI_PRIO_CTRL;
> +		*mask = KSZ9477_PORT_802_1P_PRIO_ENABLE |
> +			KSZ9477_PORT_DIFFSERV_PRIO_ENABLE;
> +	}
> +}
> +
> +/**
> + * ksz_port_set_apptrust - Sets the apptrust selectors for a port on a KSZ
> + *			   switch
> + * @ds: Pointer to the DSA switch structure
> + * @port: Port number for which to set the apptrust selectors
> + * @sel: Array of apptrust selectors to set
> + * @nsel: Number of apptrust selectors in the array
> + *
> + * This function sets the apptrust selectors for the specified port on
> +a KSZ
> + * switch.
> + *
> + * Return: 0 on success, or a negative error code on failure  */ int
> +ksz_port_set_apptrust(struct dsa_switch *ds, int port,
> +			  const u8 *sel, int nsel)
> +{
> +	const struct ksz_apptrust_map *map;
> +	struct ksz_device *dev = ds->priv;
> +	int reg, i, ret;
> +	u8 data = 0;
> +	u8 mask;
> +
> +	ret = ksz_port_set_apptrust_validate(dev, port, sel, nsel);
> +	if (ret)
> +		return ret;
> +
> +	ksz_get_apptrus_map_and_reg(dev, &map, &reg, &mask);
> +
> +	for (i = 0; i < nsel; i++) {
> +		int j;
> +
> +		for (j = 0; j < ARRAY_SIZE(ksz_supported_apptrust); j++) {
> +			if (sel[i] != ksz_supported_apptrust[j])
> +				continue;
> +
> +			data |= map[j].bit;
> +			break;
> +		}
> +	}
> +
> +	return ksz_prmw8(dev, port, reg, mask, data); }
> +
> +/**
> + * ksz_port_get_apptrust - Retrieves the apptrust selectors for a port on a KSZ
> + *			   switch
> + * @ds: Pointer to the DSA switch structure
> + * @port: Port number for which to get the apptrust selectors
> + * @sel: Array to store the apptrust selectors
> + * @nsel: Number of apptrust selectors in the array
> + *
> + * This function fetches the apptrust selectors for the specified port
> +on a KSZ
> + * switch.
> + *
> + * Return: 0 on success, or a negative error code on failure  */ int
> +ksz_port_get_apptrust(struct dsa_switch *ds, int port, u8 *sel, int
> +*nsel) {
> +	const struct ksz_apptrust_map *map;
> +	struct ksz_device *dev = ds->priv;
> +	int reg, i, ret;
> +	u8 data;
> +	u8 mask;
> +
> +	ksz_get_apptrus_map_and_reg(dev, &map, &reg, &mask);
> +
> +	ret = ksz_pread8(dev, port, reg, &data);
> +	if (ret)
> +		return ret;
> +
> +	*nsel = 0;
> +	for (i = 0; i < ARRAY_SIZE(ksz_supported_apptrust); i++) {
> +		if (data & map[i].bit)
> +			sel[(*nsel)++] = ksz_supported_apptrust[i];
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * ksz_dcb_init_port - Initializes the DCB configuration for a port on
> +a KSZ
> + * @dev: Pointer to the KSZ switch device structure
> + * @port: Port number for which to initialize the DCB configuration
> + *
> + * This function initializes the DCB configuration for the specified
> +port on a
> + * KSZ switch. Particular DCB configuration is set for the port,
> +including the
> + * default priority and apptrust selectors.
> + * The default priority is set to Best Effort, and the apptrust
> +selectors are
> + * set to all supported selectors.
> + *
> + * Return: 0 on success, or a negative error code on failure  */ int
> +ksz_dcb_init_port(struct ksz_device *dev, int port) {
> +	int ret, ipv;
> +
> +	if (is_ksz8(dev))
> +		ipv = ieee8021q_tt_to_tc(IEEE8021Q_TT_BE,
> +					 dev->info->num_tx_queues);
> +	else
> +		ipv = IEEE8021Q_TT_BE;
> +
> +	/* Set the default priority for the port to Best Effort */
> +	ret = ksz_port_set_default_prio(dev->ds, port, ipv);
> +	if (ret)
> +		return ret;
> +
> +	return ksz_port_set_apptrust(dev->ds, port, ksz_supported_apptrust,
> +				     ARRAY_SIZE(ksz_supported_apptrust));
> +}
> +
> +/**
> + * ksz_dcb_init - Initializes the DCB configuration for a KSZ switch
> + * @dev: Pointer to the KSZ switch device structure
> + *
> + * This function initializes the DCB configuration for a KSZ switch.
> +The global
> + * DSCP-to-priority mapping table is initialized.
> + *
> + * Return: 0 on success, or a negative error code on failure  */ int
> +ksz_dcb_init(struct ksz_device *dev) {
> +	int ret;
> +
> +	ret = ksz_init_global_dscp_map(dev);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> diff --git a/drivers/net/dsa/microchip/ksz_dcb.h
> b/drivers/net/dsa/microchip/ksz_dcb.h
> new file mode 100644
> index 0000000000000..254c0e7bdafca
> --- /dev/null
> +++ b/drivers/net/dsa/microchip/ksz_dcb.h
> @@ -0,0 +1,21 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (c) 2024 Pengutronix, Oleksij Rempel
> +<kernel@pengutronix.de> */
> +
> +#ifndef __KSZ_DCB_H
> +#define __KSZ_DCB_H
> +
> +#include <net/dsa.h>
> +
> +#include "ksz_common.h"
> +
> +int ksz_port_get_default_prio(struct dsa_switch *ds, int port); int
> +ksz_port_set_default_prio(struct dsa_switch *ds, int port, u8 prio);
> +int ksz_port_get_dscp_prio(struct dsa_switch *ds, int port, u8 dscp);
> +int ksz_port_set_apptrust(struct dsa_switch *ds, int port,
> +			  const unsigned char *sel,
> +			  int nsel);
> +int ksz_port_get_apptrust(struct dsa_switch *ds, int port, u8 *sel, int
> +*nsel); int ksz_dcb_init_port(struct ksz_device *dev, int port); int
> +ksz_dcb_init(struct ksz_device *dev);
> +
> +#endif /* __KSZ_DCB_H */
> --
> 2.39.2
>