[Skiboot] [PATCH 4/7] capp/phb4: Force CAPP to PCIe mode during kernel shutdown

[Vaibhav Jain]

This patch introduces a new opal syncer for PHB4 named
phb4_host_sync_reset(). We register this opal syncer when CAPP is
activated successfully in phb4_set_capi_mode() so that it will be
called at kernel shutdown during fast-reset.

The function will then repeatedly call phb->ops->set_capi_mode() to
switch switch CAPP to PCIe mode. In case set_capi_mode() indicates its
OPAL_BUSY. It calls slot->ops.run_sm() to ensure that Opal slot reset
state machine makes forward progress.

Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
 hw/phb4.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/hw/phb4.c b/hw/phb4.c
index 4284c467..615cda66 100644
--- a/hw/phb4.c
+++ b/hw/phb4.c
@@ -2747,6 +2747,36 @@ static void phb4_training_trace(struct phb4 *p)
 	}
 }
 
+/*
+ * Trigger a creset to disable CAPI mode on kernel shutdown.
+ *
+ * This helper is called repeatedly by the host sync notifier mechanism, which
+ * relies on the kernel to regularly poll the OPAL_SYNC_HOST_REBOOT call as it
+ * shuts down.
+ */
+static bool phb4_host_sync_reset(void *data)
+{
+	struct phb4 *p = (struct phb4 *)data;
+	struct phb *phb = &p->phb;
+	struct pci_slot *slot = p->phb.slot;
+	int64_t rc = 0;
+
+	/* Make sure no-one modifies the phb flags while we are active */
+	phb_lock(phb);
+
+	/* Call phb ops to disable capi */
+	rc = phb->ops->set_capi_mode(phb, OPAL_PHB_CAPI_MODE_PCIE,
+				       phb->ops->get_reserved_pe_number(phb));
+	if (rc == OPAL_BUSY) {
+		/* Run the phb reset state machine */
+		rc = slot->ops.run_sm(slot);
+	}
+
+	phb_unlock(phb);
+
+	return rc <= OPAL_SUCCESS;
+}
+
 static int64_t phb4_poll_link(struct pci_slot *slot)
 {
 	struct phb4 *p = phb_to_phb4(slot->phb);
@@ -4381,9 +4411,13 @@ static int64_t phb4_set_capi_mode(struct phb *phb, uint64_t mode,
 					(CAPP_MAX_STQ_ENGINES |
 					 CAPP_MIN_DMA_READ_ENGINES)));
 
-		if (ret == OPAL_SUCCESS)
+		if (ret == OPAL_SUCCESS) {
+			/* register notification on system shutdown */
+			opal_add_host_sync_notifier(&phb4_host_sync_reset, p);
+
 			/* Disable fast reboot for CAPP */
 			disable_fast_reboot("CAPP being enabled");
+		}
 		else
 			/* In case of an error mark the PHB detached */
 			chip->capp_phb4_attached_mask ^= 1 << p->index;
-- 
2.17.1