[net-next RFC PATCH v5 02/10] net: phylink: introduce internal phylink PCS handling

Christian Marangi
2026-05-05T18:27:47Z

Introduce internal handling of PCS for phylink. This is an alternative
to .mac_select_pcs that moves the selection logic of the PCS entirely to
phylink with the usage of the supported_interface value in the PCS
struct.

MAC should now provide an array of available PCS in phylink_config in
.available_pcs and fill the .num_available_pcs with the number of
elements in the array. MAC should also define a new bitmap,
pcs_interfaces, in phylink_config to define for what interface mode a
dedicated PCS is required.

On phylink_create() this array is parsed and a linked list of PCS is
created based on the PCS passed in phylink_config.
Also the supported_interface value in phylink struct is updated with the
new supported_interface from the provided PCS.

On phylink_start() every PCS in phylink PCS list gets attached to the
phylink instance. This is done by setting the phylink value in
phylink_pcs struct to the phylink instance.

On phylink_stop(), every PCS in phylink PCS list is detached from the
phylink instance. This is done by setting the phylink value in
phylink_pcs struct to NULL.

phylink_validate_mac_and_pcs(), phylink_major_config() and
phylink_inband_caps() are updated to support this new implementation
with the PCS list stored in phylink.

They will make use of phylink_validate_pcs_interface() that will loop
for every PCS in the phylink PCS available list and find one that supports
the passed interface.

phylink_validate_pcs_interface() applies the same logic of .mac_select_pcs
where if a supported_interface value is not set for the PCS struct, then
it's assumed every interface is supported.

A MAC is required to implement either a .mac_select_pcs or make use of
the PCS list implementation. Implementing both will result in a fail
on MAC/PCS validation.

phylink value in phylink_pcs struct with this implementation is used to
track from PCS side when it's attached to a phylink instance. PCS driver
will make use of this information to correctly detach from a phylink
instance if needed.

The .mac_select_pcs implementation is not changed but it's expected that
every MAC driver migrates to the new implementation to later deprecate
and remove .mac_select_pcs.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
drivers/net/phy/phylink.c | 149 +++++++++++++++++++++++++++++++++-----
include/linux/phylink.h | 11 +++
2 files changed, 141 insertions(+), 19 deletions(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 4d59c0dd78db..1a261060d78e 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -60,6 +60,9 @@ struct phylink {
/* The link configuration settings */
struct phylink_link_state link_config;

+ /* List of available PCS */
+ struct list_head pcs_list;
+
/* What interface are supported by the current link.
* Can change on removal or addition of new PCS.
*/
@@ -154,6 +157,8 @@ static const phy_interface_t phylink_sfp_interface_preference[] = {

static DECLARE_PHY_INTERFACE_MASK(phylink_sfp_interfaces);

+static void phylink_run_resolve(struct phylink *pl);
+
/**
* phylink_set_port_modes() - set the port type modes in the ethtool mask
* @mask: ethtool link mode mask
@@ -518,22 +523,59 @@ static void phylink_validate_mask_caps(unsigned long *supported,
linkmode_and(state->advertising, state->advertising, mask);
}

+static int phylink_validate_pcs_interface(struct phylink_pcs *pcs,
+ phy_interface_t interface)
+{
+ /* If PCS define an empty supported_interfaces value, assume
+ * all interface are supported.
+ */
+ if (phy_interface_empty(pcs->supported_interfaces))
+ return 0;
+
+ /* Ensure that this PCS supports the interface mode */
+ if (!test_bit(interface, pcs->supported_interfaces))
+ return -EINVAL;
+
+ return 0;
+}
+
static int phylink_validate_mac_and_pcs(struct phylink *pl,
unsigned long *supported,
struct phylink_link_state *state)
{
- struct phylink_pcs *pcs = NULL;
unsigned long capabilities;
+ struct phylink_pcs *pcs;
+ bool pcs_found = false;
int ret;

/* Get the PCS for this interface mode */
if (pl->mac_ops->mac_select_pcs) {
+ /* Make sure either PCS internal validation or .mac_select_pcs
+ * is used. Return error if both are defined.
+ */
+ if (!list_empty(&pl->pcs_list)) {
+ phylink_err(pl, "either phylink_pcs_add() or .mac_select_pcs must be used\n");
+ return -EINVAL;
+ }
+
pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
if (IS_ERR(pcs))
return PTR_ERR(pcs);
+
+ pcs_found = !!pcs;
+ } else {
+ /* Check every assigned PCS and search for one that supports
+ * the interface.
+ */
+ list_for_each_entry(pcs, &pl->pcs_list, list) {
+ if (!phylink_validate_pcs_interface(pcs, state->interface)) {
+ pcs_found = true;
+ break;
+ }
+ }
}

- if (pcs) {
+ if (pcs_found) {
/* The PCS, if present, must be setup before phylink_create()
* has been called. If the ops is not initialised, print an
* error and backtrace rather than oopsing the kernel.
@@ -545,13 +587,10 @@ static int phylink_validate_mac_and_pcs(struct phylink *pl,
return -EINVAL;
}

- /* Ensure that this PCS supports the interface which the MAC
- * returned it for. It is an error for the MAC to return a PCS
- * that does not support the interface mode.
- */
- if (!phy_interface_empty(pcs->supported_interfaces) &&
- !test_bit(state->interface, pcs->supported_interfaces)) {
- phylink_err(pl, "MAC returned PCS which does not support %s\n",
+ /* Recheck PCS to handle legacy way for .mac_select_pcs */
+ ret = phylink_validate_pcs_interface(pcs, state->interface);
+ if (ret) {
+ phylink_err(pl, "selected PCS does not support %s\n",
phy_modes(state->interface));
return -EINVAL;
}
@@ -965,12 +1004,22 @@ static unsigned int phylink_inband_caps(struct phylink *pl,
phy_interface_t interface)
{
struct phylink_pcs *pcs;
+ bool pcs_found = false;

- if (!pl->mac_ops->mac_select_pcs)
- return 0;
+ if (pl->mac_ops->mac_select_pcs) {
+ pcs = pl->mac_ops->mac_select_pcs(pl->config,
+ interface);
+ pcs_found = !!pcs;
+ } else {
+ list_for_each_entry(pcs, &pl->pcs_list, list) {
+ if (!phylink_validate_pcs_interface(pcs, interface)) {
+ pcs_found = true;
+ break;
+ }
+ }
+ }

- pcs = pl->mac_ops->mac_select_pcs(pl->config, interface);
- if (!pcs)
+ if (!pcs_found)
return 0;

return phylink_pcs_inband_caps(pcs, interface);
@@ -1265,10 +1314,36 @@ static void phylink_major_config(struct phylink *pl, bool restart,
pl->major_config_failed = true;
return;
}
+ /* Find a PCS in available PCS list for the requested interface.
+ * This doesn't overwrite the previous .mac_select_pcs as either
+ * .mac_select_pcs or PCS list implementation are permitted.
+ *
+ * Skip searching if the MAC doesn't require a dedicaed PCS for
+ * the requested interface.
+ */
+ } else if (test_bit(state->interface, pl->config->pcs_interfaces)) {
+ bool pcs_found = false;
+
+ list_for_each_entry(pcs, &pl->pcs_list, list) {
+ if (!phylink_validate_pcs_interface(pcs,
+ state->interface)) {
+ pcs_found = true;
+ break;
+ }
+ }
+
+ if (!pcs_found) {
+ phylink_err(pl,
+ "couldn't find a PCS for %s\n",
+ phy_modes(state->interface));

- pcs_changed = pl->pcs != pcs;
+ pl->major_config_failed = true;
+ return;
+ }
}

+ pcs_changed = pl->pcs != pcs;
+
phylink_pcs_neg_mode(pl, pcs, state->interface, state->advertising);

phylink_dbg(pl, "major config, active %s/%s/%s\n",
@@ -1295,11 +1370,13 @@ static void phylink_major_config(struct phylink *pl, bool restart,
if (pcs_changed) {
phylink_pcs_disable(pl->pcs);

- if (pl->pcs)
- pl->pcs->phylink = NULL;
+ if (pl->mac_ops->mac_select_pcs) {
+ if (pl->pcs)
+ pl->pcs->phylink = NULL;

- if (pcs)
- pcs->phylink = pl;
+ if (pcs)
+ pcs->phylink = pl;
+ }

pl->pcs = pcs;
}
@@ -1855,8 +1932,9 @@ struct phylink *phylink_create(struct phylink_config *config,
phy_interface_t iface,
const struct phylink_mac_ops *mac_ops)
{
+ struct phylink_pcs *pcs;
struct phylink *pl;
- int ret;
+ int i, ret;

/* Validate the supplied configuration */
if (phy_interface_empty(config->supported_interfaces)) {
@@ -1872,9 +1950,21 @@ struct phylink *phylink_create(struct phylink_config *config,
mutex_init(&pl->phydev_mutex);
mutex_init(&pl->state_mutex);
INIT_WORK(&pl->resolve, phylink_resolve);
+ INIT_LIST_HEAD(&pl->pcs_list);
+
+ /* Fill the PCS list with available PCS from phylink config */
+ for (i = 0; i < config->num_available_pcs; i++) {
+ pcs = config->available_pcs[i];
+
+ list_add(&pcs->list, &pl->pcs_list);
+ }

phy_interface_copy(pl->supported_interfaces,
config->supported_interfaces);
+ list_for_each_entry(pcs, &pl->pcs_list, list)
+ phy_interface_or(pl->supported_interfaces,
+ pl->supported_interfaces,
+ pcs->supported_interfaces);

pl->config = config;
if (config->type == PHYLINK_NETDEV) {
@@ -1953,10 +2043,16 @@ EXPORT_SYMBOL_GPL(phylink_create);
*/
void phylink_destroy(struct phylink *pl)
{
+ struct phylink_pcs *pcs, *tmp;
+
sfp_bus_del_upstream(pl->sfp_bus);
if (pl->link_gpio)
gpiod_put(pl->link_gpio);

+ /* Remove every PCS from phylink PCS list */
+ list_for_each_entry_safe(pcs, tmp, &pl->pcs_list, list)
+ list_del(&pcs->list);
+
cancel_work_sync(&pl->resolve);
kfree(pl);
}
@@ -2437,6 +2533,7 @@ static irqreturn_t phylink_link_handler(int irq, void *data)
*/
void phylink_start(struct phylink *pl)
{
+ struct phylink_pcs *pcs;
bool poll = false;

ASSERT_RTNL();
@@ -2463,6 +2560,10 @@ void phylink_start(struct phylink *pl)

pl->pcs_state = PCS_STATE_STARTED;

+ /* link available PCS to phylink struct */
+ list_for_each_entry(pcs, &pl->pcs_list, list)
+ pcs->phylink = pl;
+
phylink_enable_and_run_resolve(pl, PHYLINK_DISABLE_STOPPED);

if (pl->cfg_link_an_mode == MLO_AN_FIXED && pl->link_gpio) {
@@ -2507,6 +2608,8 @@ EXPORT_SYMBOL_GPL(phylink_start);
*/
void phylink_stop(struct phylink *pl)
{
+ struct phylink_pcs *pcs;
+
ASSERT_RTNL();

if (pl->sfp_bus)
@@ -2524,6 +2627,14 @@ void phylink_stop(struct phylink *pl)
pl->pcs_state = PCS_STATE_DOWN;

phylink_pcs_disable(pl->pcs);
+
+ /* Drop link between phylink and PCS */
+ list_for_each_entry(pcs, &pl->pcs_list, list)
+ pcs->phylink = NULL;
+
+ /* Restore original supported interfaces */
+ phy_interface_copy(pl->supported_interfaces,
+ pl->config->supported_interfaces);
}
EXPORT_SYMBOL_GPL(phylink_stop);

diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 2bc0db3d52ac..9c5a43febde1 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -151,6 +151,8 @@ enum phylink_op_type {
* if MAC link is at %MLO_AN_FIXED mode.
* @supported_interfaces: bitmap describing which PHY_INTERFACE_MODE_xxx
* are supported by the MAC/PCS.
+ * @pcs_interfaces: bitmap describing for which PHY_INTERFACE_MODE_xxx a
+ * dedicated PCS is required.
* @lpi_interfaces: bitmap describing which PHY interface modes can support
* LPI signalling.
* @mac_capabilities: MAC pause/speed/duplex capabilities.
@@ -160,6 +162,8 @@ enum phylink_op_type {
* @wol_phy_legacy: Use Wake-on-Lan with PHY even if phy_can_wakeup() is false
* @wol_phy_speed_ctrl: Use phy speed control on suspend/resume
* @wol_mac_support: Bitmask of MAC supported %WAKE_* options
+ * @available_pcs: array of available phylink_pcs PCS
+ * @num_available_pcs: num of available phylink_pcs PCS
*/
struct phylink_config {
struct device *dev;
@@ -172,6 +176,7 @@ struct phylink_config {
void (*get_fixed_state)(struct phylink_config *config,
struct phylink_link_state *state);
DECLARE_PHY_INTERFACE_MASK(supported_interfaces);
+ DECLARE_PHY_INTERFACE_MASK(pcs_interfaces);
DECLARE_PHY_INTERFACE_MASK(lpi_interfaces);
unsigned long mac_capabilities;
unsigned long lpi_capabilities;
@@ -182,6 +187,9 @@ struct phylink_config {
bool wol_phy_legacy;
bool wol_phy_speed_ctrl;
u32 wol_mac_support;
+
+ struct phylink_pcs **available_pcs;
+ unsigned int num_available_pcs;
};

void phylink_limit_mac_speed(struct phylink_config *config, u32 max_speed);
@@ -497,6 +505,9 @@ struct phylink_pcs {
struct phylink *phylink;
bool poll;
bool rxc_always_on;
+
+ /* private: */
+ struct list_head list;
};

/**
--
2.53.0