npu2-opencapi: Use presence detection

Presence detection is not part of the opencapi specification. So each
platform may choose to implement it the way it wants.

All current platforms implement it through an i2c device where we can
query a pin to know if a device is connected or not. ZZ and Zaius have
a similar design and even use the same i2c information and pin
numbers.
However, presence detection on older ZZ planar (older than v4) doesn't
work, so we don't activate it for now, until our lab systems are
upgraded and it's better tested.

Presence detection on witherspoon is still being worked on. It's
shaping up to be quite different, so we may have to revisit the topic
in a later patch.

Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

1 files changed, 99 insertions, 22 deletions

diff --git a/hw/npu2-opencapi.c b/hw/npu2-opencapi.c
index 91b5c05..e9e5bbc 100644
--- a/hw/npu2-opencapi.c
+++ b/hw/npu2-opencapi.c
@@ -829,6 +829,44 @@ static void reset_ocapi_device(struct npu2_dev *dev)
 	}
 }
 
+static bool i2c_presence_detect(struct npu2_dev *dev)
+{
+	uint8_t state, data;
+	int rc;
+
+	/*
+	 * Opencapi presence detection is done through i2c
+	 *
+	 * Lagrange platforms (ZZ, Zaius) use the same default mechanism.
+	 * Witherspoon will need a specific implementation, TBD.
+	 */
+	rc = i2c_request_send(dev->i2c_port_id_ocapi,
+			platform.ocapi->i2c_presence_addr,
+			SMBUS_READ, 0, 1,
+			&state, 1, 120);
+	if (rc) {
+		prlog(PR_ERR, "OCAPI: error detecting link presence: %d\n",
+			rc);
+		return true; /* assume link exists */
+	}
+
+	prlog(PR_DEBUG, "OCAPI: I2C presence detect: 0x%x\n", state);
+
+	switch (dev->index) {
+	case 2:
+		data = platform.ocapi->i2c_presence_odl0;
+		break;
+	case 3:
+		data = platform.ocapi->i2c_presence_odl1;
+		break;
+	default:
+		prlog(PR_ERR, "OCAPI: presence detection on invalid link\n");
+		return true;
+	}
+	/* Presence detect bits are active low */
+	return !(state & data);
+}
+
 static int odl_train(uint32_t gcid, uint32_t index, struct npu2_dev *dev)
 {
 	uint64_t reg, config_xscom;
@@ -896,6 +934,20 @@ static int odl_train(uint32_t gcid, uint32_t index, struct npu2_dev *dev)
 	return OPAL_HARDWARE;
 }
 
+static int64_t npu2_opencapi_get_presence_state(struct pci_slot *slot,
+						uint8_t *val)
+{
+	bool present;
+	struct npu2_dev *dev = phb_to_npu2_dev_ocapi(slot->phb);
+
+	if (platform.ocapi->force_presence)
+		present = true;
+	else
+		present = i2c_presence_detect(dev);
+	*val = present;
+	return OPAL_SUCCESS;
+}
+
 static int64_t npu2_opencapi_get_link_state(struct pci_slot *slot, uint8_t *val)
 {
 	struct npu2_dev *dev = phb_to_npu2_dev_ocapi(slot->phb);
@@ -926,9 +978,9 @@ static struct pci_slot *npu2_opencapi_slot_create(struct phb *phb)
 		return slot;
 
 	/* TODO: Figure out other slot functions */
-	slot->ops.get_presence_state = NULL;
-	slot->ops.get_link_state = npu2_opencapi_get_link_state;
-	slot->ops.get_power_state = NULL;
+	slot->ops.get_presence_state  = npu2_opencapi_get_presence_state;
+	slot->ops.get_link_state      = npu2_opencapi_get_link_state;
+	slot->ops.get_power_state     = NULL;
 	slot->ops.get_attention_state = NULL;
 	slot->ops.get_latch_state     = NULL;
 	slot->ops.set_power_state     = NULL;
@@ -1264,6 +1316,48 @@ static int setup_irq(struct npu2 *p)
 
 #define LINK_TRAINING_RETRIES	5
 
+static int train_link(int chip_id, struct npu2_dev *dev)
+{
+	bool train;
+	int rc;
+	int retries = LINK_TRAINING_RETRIES;
+
+	if (platform.ocapi->force_presence)
+		train = true;
+	else
+		train = i2c_presence_detect(dev);
+	if (!train) {
+		/*
+		 * FIXME: if there's no card on the link, we should consider
+		 * powering off the unused lanes to save energy
+		 */
+		prlog(PR_INFO, "OCAPI: no card detected on link %d, chip %d\n",
+			dev->index, chip_id);
+		return -1;
+	}
+
+	do {
+		rc = odl_train(chip_id, dev->index, dev);
+	} while (rc != OPAL_SUCCESS && --retries);
+
+	if (rc != OPAL_SUCCESS && retries == 0) {
+		/**
+		 * @fwts-label OCAPILinkTrainingFailed
+		 * @fwts-advice The OpenCAPI link training procedure failed.
+		 * This indicates a hardware or firmware bug. OpenCAPI
+		 * functionality will not be available on this link.
+		 */
+		prlog(PR_ERR,
+			"OCAPI: Link %d on chip %u failed to train\n",
+			dev->index, chip_id);
+		prlog(PR_ERR, "OCAPI: Final link status: %016llx\n",
+			get_odl_status(chip_id, dev->index));
+		return -1;
+	}
+
+	return 0;
+}
+
 static void npu2_opencapi_setup_device(struct dt_node *dn_link, struct npu2 *n,
 				       struct npu2_dev *dev)
 {
@@ -1272,7 +1366,6 @@ static void npu2_opencapi_setup_device(struct dt_node *dn_link, struct npu2 *n,
 	struct pci_slot *slot;
 	char port_name[17];
 	uint64_t mm_win[2];
-	int retries = LINK_TRAINING_RETRIES;
 	int rc;
 
 	dev_index = dt_prop_get_u32(dn_link, "ibm,npu-link-index");
@@ -1367,27 +1460,11 @@ static void npu2_opencapi_setup_device(struct dt_node *dn_link, struct npu2 *n,
 		break;
 
 	case NPU2_TRAIN_DEFAULT:
-		do {
-			rc = odl_train(n->chip_id, dev->index, dev);
-		} while (rc != OPAL_SUCCESS && --retries);
-
-		if (rc != OPAL_SUCCESS && retries == 0) {
-			/**
-			 * @fwts-label OCAPILinkTrainingFailed
-			 * @fwts-advice The OpenCAPI link training procedure failed.
-			 * This indicates a hardware or firmware bug. OpenCAPI
-			 * functionality will not be available on this link.
-			 */
-			prlog(PR_ERR,
-				"OCAPI: Link %d on chip %u failed to train\n",
-				dev->index, n->chip_id);
-			prlog(PR_ERR, "OCAPI: Final link status: %016llx\n",
-				get_odl_status(n->chip_id, dev->index));
+		rc = train_link(n->chip_id, dev);
+		if (rc)
 			goto failed;
-		}
 
 		otl_enabletx(n->chip_id, n->xscom_base, dev->index);
-
 		slot = npu2_opencapi_slot_create(&dev->phb_ocapi);
 		if (!slot) {
 			/**