net: phylink: introduce helpers for replaying link callbacks

Some drivers of MAC + tightly integrated PCS (example: SJA1105 + XPCS
covered by same reset domain) need to perform resets at runtime.

The reset is triggered by the MAC driver, and it needs to restore its
and the PCS' registers, all invisible to phylink.

However, there is a desire to simplify the API through which the MAC and
the PCS interact, so this becomes challenging.

Phylink holds all the necessary state to help with this operation, and
can offer two helpers which walk the MAC and PCS drivers again through
the callbacks required during a destructive reset operation. The
procedure is as follows:

Before reset, MAC driver calls phylink_replay_link_begin():
- Triggers phylink mac_link_down() and pcs_link_down() methods

After reset, MAC driver calls phylink_replay_link_end():
- Triggers phylink mac_config() -> pcs_config() -> mac_link_up() ->
  pcs_link_up() methods.

MAC and PCS registers are restored with no other custom driver code.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/20260119121954.1624535-3-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index f29cd4d7aca2416d828ee1848b1b62c62bc9a807..7641f1f41e39a2ae75cb63e4eba43b27714b3a5b 100644 (file)
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -28,6 +28,7 @@ enum {
        PHYLINK_DISABLE_STOPPED,
        PHYLINK_DISABLE_LINK,
        PHYLINK_DISABLE_MAC_WOL,
+       PHYLINK_DISABLE_REPLAY,
 
        PCS_STATE_DOWN = 0,
        PCS_STATE_STARTING,
@@ -77,6 +78,7 @@ struct phylink {
 
        bool link_failed;
        bool suspend_link_up;
+       bool force_major_config;
        bool major_config_failed;
        bool mac_supports_eee_ops;
        bool mac_supports_eee;
@@ -1684,9 +1686,10 @@ static void phylink_resolve(struct work_struct *w)
        if (pl->act_link_an_mode != MLO_AN_FIXED)
                phylink_apply_manual_flow(pl, &link_state);
 
-       if (mac_config && link_state.interface != pl->link_config.interface) {
-               /* The interface has changed, so force the link down and then
-                * reconfigure.
+       if ((mac_config && link_state.interface != pl->link_config.interface) ||
+           pl->force_major_config) {
+               /* The interface has changed or a forced major configuration
+                * was requested, so force the link down and then reconfigure.
                 */
                if (cur_link_state) {
                        phylink_link_down(pl);
@@ -1694,6 +1697,7 @@ static void phylink_resolve(struct work_struct *w)
                }
                phylink_major_config(pl, false, &link_state);
                pl->link_config.interface = link_state.interface;
+               pl->force_major_config = false;
        }
 
        /* If configuration of the interface failed, force the link down
@@ -4357,6 +4361,57 @@ void phylink_mii_c45_pcs_get_state(struct mdio_device *pcs,
 }
 EXPORT_SYMBOL_GPL(phylink_mii_c45_pcs_get_state);
 
+/**
+ * phylink_replay_link_begin() - begin replay of link callbacks for driver
+ *                              which loses state
+ * @pl: a pointer to a &struct phylink returned from phylink_create()
+ *
+ * Helper for MAC drivers which may perform a destructive reset at runtime.
+ * Both the own driver's mac_link_down() method is called, as well as the
+ * pcs_link_down() method of the split PCS (if any).
+ *
+ * This is similar to phylink_stop(), except it does not alter the state of
+ * the phylib PHY (it is assumed that it is not affected by the MAC destructive
+ * reset).
+ */
+void phylink_replay_link_begin(struct phylink *pl)
+{
+       ASSERT_RTNL();
+
+       phylink_run_resolve_and_disable(pl, PHYLINK_DISABLE_REPLAY);
+}
+EXPORT_SYMBOL_GPL(phylink_replay_link_begin);
+
+/**
+ * phylink_replay_link_end() - end replay of link callbacks for driver
+ *                            which lost state
+ * @pl: a pointer to a &struct phylink returned from phylink_create()
+ *
+ * Helper for MAC drivers which may perform a destructive reset at runtime.
+ * Both the own driver's mac_config() and mac_link_up() methods, as well as the
+ * pcs_config() and pcs_link_up() method of the split PCS (if any), are called.
+ *
+ * This is similar to phylink_start(), except it does not alter the state of
+ * the phylib PHY.
+ *
+ * One must call this method only within the same rtnl_lock() critical section
+ * as a previous phylink_replay_link_start().
+ */
+void phylink_replay_link_end(struct phylink *pl)
+{
+       ASSERT_RTNL();
+
+       if (WARN(!test_bit(PHYLINK_DISABLE_REPLAY,
+                          &pl->phylink_disable_state),
+                "phylink_replay_link_end() called without a prior phylink_replay_link_begin()\n"))
+               return;
+
+       pl->force_major_config = true;
+       phylink_enable_and_run_resolve(pl, PHYLINK_DISABLE_REPLAY);
+       flush_work(&pl->resolve);
+}
+EXPORT_SYMBOL_GPL(phylink_replay_link_end);
+
 static int __init phylink_init(void)
 {
        for (int i = 0; i < ARRAY_SIZE(phylink_sfp_interface_preference); ++i)

diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 20996f5778d1c9f5934b143f031e39ed651a5b9d..2bc0db3d52ac8d51e1180e197e5af9ef61878e06 100644 (file)
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -837,4 +837,9 @@ void phylink_mii_c45_pcs_get_state(struct mdio_device *pcs,
 
 void phylink_decode_usxgmii_word(struct phylink_link_state *state,
                                 uint16_t lpa);
+
+void phylink_replay_link_begin(struct phylink *pl);
+
+void phylink_replay_link_end(struct phylink *pl);
+
 #endif