net: dsa: microchip: Ensure Stable PME Pin State for Wake-on-LAN

Ensures a stable PME (Power Management Event) pin state by disabling PME
on system start and enabling it on shutdown only if WoL (Wake-on-LAN) is
configured. This is needed to avoid issues with some PMICs (Power
Management ICs).

Signed-off-by: Oleksij Rempel <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/dsa/microchip/ksz9477.c

···
 	return 0;
 }
 
+/**
+ * ksz9477_wol_pre_shutdown - Prepares the switch device for shutdown while
+ *                            considering Wake-on-LAN (WoL) settings.
+ * @dev: The switch device structure.
+ * @wol_enabled: Pointer to a boolean which will be set to true if WoL is
+ *               enabled on any port.
+ *
+ * This function prepares the switch device for a safe shutdown while taking
+ * into account the Wake-on-LAN (WoL) settings on the user ports. It updates
+ * the wol_enabled flag accordingly to reflect whether WoL is active on any
+ * port.
+ */
+void ksz9477_wol_pre_shutdown(struct ksz_device *dev, bool *wol_enabled)
+{
+	struct dsa_port *dp;
+	int ret;
+
+	*wol_enabled = false;
+
+	if (!dev->wakeup_source)
+		return;
+
+	dsa_switch_for_each_user_port(dp, dev->ds) {
+		u8 pme_ctrl = 0;
+
+		ret = ksz_pread8(dev, dp->index, REG_PORT_PME_CTRL, &pme_ctrl);
+		if (!ret && pme_ctrl)
+			*wol_enabled = true;
+
+		/* make sure there are no pending wake events which would
+		 * prevent the device from going to sleep/shutdown.
+		 */
+		ksz9477_handle_wake_reason(dev, dp->index);
+	}
+
+	/* Now we are save to enable PME pin. */
+	if (*wol_enabled)
+		ksz_write8(dev, REG_SW_PME_CTRL, PME_ENABLE);
+}
+
 static int ksz9477_wait_vlan_ctrl_ready(struct ksz_device *dev)
 {
 	unsigned int val;
···
 
 	/* enable global MIB counter freeze function */
 	ksz_cfg(dev, REG_SW_MAC_CTRL_6, SW_MIB_COUNTER_FREEZE, true);
+
+	/* Make sure PME (WoL) is not enabled. If requested, it will be
+	 * enabled by ksz9477_wol_pre_shutdown(). Otherwise, some PMICs do not
+	 * like PME events changes before shutdown.
+	 */
+	ksz_write8(dev, REG_SW_PME_CTRL, 0);
 
 	return 0;
 }

drivers/net/dsa/microchip/ksz9477.h

···
 		     struct ethtool_wolinfo *wol);
 int ksz9477_set_wol(struct ksz_device *dev, int port,
 		    struct ethtool_wolinfo *wol);
+void ksz9477_wol_pre_shutdown(struct ksz_device *dev, bool *wol_enabled);
 
 int ksz9477_port_acl_init(struct ksz_device *dev, int port);
 void ksz9477_port_acl_free(struct ksz_device *dev, int port);

drivers/net/dsa/microchip/ksz_common.c

···
 	.phylink_mac_link_up = ksz9477_phylink_mac_link_up,
 	.get_wol = ksz9477_get_wol,
 	.set_wol = ksz9477_set_wol,
+	.wol_pre_shutdown = ksz9477_wol_pre_shutdown,
 	.config_cpu_port = ksz9477_config_cpu_port,
 	.tc_cbs_set_cinc = ksz9477_tc_cbs_set_cinc,
 	.enable_stp_addr = ksz9477_enable_stp_addr,
···
  */
 void ksz_switch_shutdown(struct ksz_device *dev)
 {
-	if (dev->dev_ops->reset)
+	bool wol_enabled = false;
+
+	if (dev->dev_ops->wol_pre_shutdown)
+		dev->dev_ops->wol_pre_shutdown(dev, &wol_enabled);
+
+	if (dev->dev_ops->reset && !wol_enabled)
 		dev->dev_ops->reset(dev);
 
 	dsa_switch_shutdown(dev->ds);

drivers/net/dsa/microchip/ksz_common.h

···
 			struct ethtool_wolinfo *wol);
 	int (*set_wol)(struct ksz_device *dev, int port,
 		       struct ethtool_wolinfo *wol);
+	void (*wol_pre_shutdown)(struct ksz_device *dev, bool *wol_enabled);
 	void (*config_cpu_port)(struct dsa_switch *ds);
 	int (*enable_stp_addr)(struct ksz_device *dev);
 	int (*reset)(struct ksz_device *dev);