core/pci: Train link of PHB slots when hotplugging

The link of PHB slots must be trained after powering on. This can be
done by calling the fundamental reset callback of the slot.

We could force a reset for all the slots and have a common path in
set_power_state(). But this patch only resets the PHB slot. Some slot
implementations do a power cycle during fundamental reset, so calling
a reset after powering on would repeat that operation.

Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

core/pci-opal.c

@@ -663,7 +663,10 @@ static void rescan_slot_devices(struct pci_slot *slot)
 	struct phb *phb = slot->phb;
 	struct pci_device *pd = slot->pd;
 
-	slot->ops.prepare_link_change(slot, true);
+	/*
+	 * prepare_link_change() is called (if needed) by the state
+	 * machine during the slot reset or link polling
+	 */
 	pci_scan_bus(phb, pd->secondary_bus,
 		     pd->subordinate_bus, &pd->children, pd, true);
 	pci_add_device_nodes(phb, &pd->children, pd->dn,
@@ -678,11 +681,85 @@ static void remove_slot_devices(struct pci_slot *slot)
 	pci_remove_bus(phb, &pd->children);
 }
 
+static void link_up_timer(struct timer *t, void *data,
+			  uint64_t now __unused)
+{
+	struct pci_slot *slot = data;
+	struct phb *phb = slot->phb;
+	uint8_t link;
+	int64_t rc = 0;
+
+	if (!phb_try_lock(phb)) {
+		schedule_timer(&slot->timer, msecs_to_tb(10));
+		return;
+	}
+
+	rc = slot->ops.run_sm(slot);
+	if (rc < 0)
+		goto out;
+	if (rc > 0) {
+		schedule_timer(t, rc);
+		phb_unlock(phb);
+		return;
+	}
+
+	if (slot->ops.get_link_state(slot, &link) != OPAL_SUCCESS)
+		link = 0;
+	if (!link) {
+		rc = OPAL_HARDWARE;
+		goto out;
+	}
+
+	rescan_slot_devices(slot);
+out:
+	opal_queue_msg(OPAL_MSG_ASYNC_COMP, NULL, NULL,
+		       slot->async_token, get_slot_phandle(slot),
+		       slot->power_state, rc <= 0 ? rc : OPAL_BUSY);
+	phb_unlock(phb);
+}
+
+static bool training_needed(struct pci_slot *slot)
+{
+	struct phb *phb = slot->phb;
+	struct pci_device *pd = slot->pd;
+
+	/* only for opencapi slots for now */
+	if (!pd && phb->phb_type == phb_type_npu_v2_opencapi)
+		return true;
+	return false;
+}
+
+static void wait_for_link_up_and_rescan(struct pci_slot *slot)
+{
+	int64_t rc = 1;
+
+	/*
+	 * Links for PHB slots need to be retrained by triggering a
+	 * fundamental reset. Other slots also need to be tested for
+	 * readiness
+	 */
+	if (training_needed(slot)) {
+		pci_slot_set_state(slot, PCI_SLOT_STATE_NORMAL);
+		rc = slot->ops.freset(slot);
+		if (rc < 0) {
+			opal_queue_msg(OPAL_MSG_ASYNC_COMP, NULL, NULL,
+				       slot->async_token,
+				       get_slot_phandle(slot),
+				       slot->power_state, rc);
+			return;
+		}
+	} else {
+		pci_slot_set_state(slot, PCI_SLOT_STATE_LINK_START_POLL);
+		rc = msecs_to_tb(20);
+	}
+	init_timer(&slot->timer, link_up_timer, slot);
+	schedule_timer(&slot->timer, rc);
+}
+
 static void set_power_timer(struct timer *t __unused, void *data,
 			    uint64_t now __unused)
 {
 	struct pci_slot *slot = data;
-	uint8_t link;
 	struct phb *phb = slot->phb;
 
 	if (!phb_try_lock(phb)) {
@@ -713,23 +790,7 @@ static void set_power_timer(struct timer *t __unused, void *data,
 		}
 
 		/* Power on */
-		if (slot->ops.get_link_state(slot, &link) != OPAL_SUCCESS)
-			link = 0;
-		if (link) {
-			rescan_slot_devices(slot);
-			pci_slot_set_state(slot, PCI_SLOT_STATE_NORMAL);
-			opal_queue_msg(OPAL_MSG_ASYNC_COMP, NULL, NULL,
-				       slot->async_token, get_slot_phandle(slot),
-				       OPAL_PCI_SLOT_POWER_ON, OPAL_SUCCESS);
-		} else if (slot->retries-- == 0) {
-			pci_slot_set_state(slot, PCI_SLOT_STATE_NORMAL);
-			opal_queue_msg(OPAL_MSG_ASYNC_COMP, NULL, NULL,
-				       slot->async_token, get_slot_phandle(slot),
-				       OPAL_PCI_SLOT_POWER_ON, OPAL_BUSY);
-		} else {
-			schedule_timer(&slot->timer, msecs_to_tb(10));
-		}
-
+		wait_for_link_up_and_rescan(slot);
 		break;
 	default:
 		prlog(PR_ERR, "PCI SLOT %016llx: Unexpected state 0x%08x\n",
@@ -812,10 +873,12 @@ static int64_t opal_pci_set_power_state(uint64_t async_token,
 		init_timer(&slot->timer, set_power_timer, slot);
 		schedule_timer(&slot->timer, msecs_to_tb(10));
 	} else if (rc == OPAL_SUCCESS) {
-		if (*state == OPAL_PCI_SLOT_POWER_OFF)
+		if (*state == OPAL_PCI_SLOT_POWER_OFF) {
 			remove_slot_devices(slot);
-		else
-			rescan_slot_devices(slot);
+		} else {
+			wait_for_link_up_and_rescan(slot);
+			rc = OPAL_ASYNC_COMPLETION;
+		}
 	}
 
 	phb_unlock(phb);