1 files changed, 494 insertions, 51 deletions

diff --git a/drivers/gpu/drm/i915/intel_guc_ct.c b/drivers/gpu/drm/i915/intel_guc_ct.c
index 24ad55752396..371b6005954a 100644
--- a/drivers/gpu/drm/i915/intel_guc_ct.c
+++ b/drivers/gpu/drm/i915/intel_guc_ct.c
@@ -24,14 +24,49 @@
 #include "i915_drv.h"
 #include "intel_guc_ct.h"
 
+#ifdef CONFIG_DRM_I915_DEBUG_GUC
+#define CT_DEBUG_DRIVER(...)	DRM_DEBUG_DRIVER(__VA_ARGS__)
+#else
+#define CT_DEBUG_DRIVER(...)	do { } while (0)
+#endif
+
+struct ct_request {
+	struct list_head link;
+	u32 fence;
+	u32 status;
+	u32 response_len;
+	u32 *response_buf;
+};
+
+struct ct_incoming_request {
+	struct list_head link;
+	u32 msg[];
+};
+
 enum { CTB_SEND = 0, CTB_RECV = 1 };
 
 enum { CTB_OWNER_HOST = 0 };
 
+static void ct_incoming_request_worker_func(struct work_struct *w);
+
+/**
+ * intel_guc_ct_init_early - Initialize CT state without requiring device access
+ * @ct: pointer to CT struct
+ */
 void intel_guc_ct_init_early(struct intel_guc_ct *ct)
 {
 	/* we're using static channel owners */
 	ct->host_channel.owner = CTB_OWNER_HOST;
+
+	spin_lock_init(&ct->lock);
+	INIT_LIST_HEAD(&ct->pending_requests);
+	INIT_LIST_HEAD(&ct->incoming_requests);
+	INIT_WORK(&ct->worker, ct_incoming_request_worker_func);
+}
+
+static inline struct intel_guc *ct_to_guc(struct intel_guc_ct *ct)
+{
+	return container_of(ct, struct intel_guc, ct);
 }
 
 static inline const char *guc_ct_buffer_type_to_str(u32 type)
@@ -49,8 +84,8 @@ static inline const char *guc_ct_buffer_type_to_str(u32 type)
 static void guc_ct_buffer_desc_init(struct guc_ct_buffer_desc *desc,
 				    u32 cmds_addr, u32 size, u32 owner)
 {
-	DRM_DEBUG_DRIVER("CT: desc %p init addr=%#x size=%u owner=%u\n",
-			 desc, cmds_addr, size, owner);
+	CT_DEBUG_DRIVER("CT: desc %p init addr=%#x size=%u owner=%u\n",
+			desc, cmds_addr, size, owner);
 	memset(desc, 0, sizeof(*desc));
 	desc->addr = cmds_addr;
 	desc->size = size;
@@ -59,8 +94,8 @@ static void guc_ct_buffer_desc_init(struct guc_ct_buffer_desc *desc,
 
 static void guc_ct_buffer_desc_reset(struct guc_ct_buffer_desc *desc)
 {
-	DRM_DEBUG_DRIVER("CT: desc %p reset head=%u tail=%u\n",
-			 desc, desc->head, desc->tail);
+	CT_DEBUG_DRIVER("CT: desc %p reset head=%u tail=%u\n",
+			desc, desc->head, desc->tail);
 	desc->head = 0;
 	desc->tail = 0;
 	desc->is_in_error = 0;
@@ -79,7 +114,7 @@ static int guc_action_register_ct_buffer(struct intel_guc *guc,
 	int err;
 
 	/* Can't use generic send(), CT registration must go over MMIO */
-	err = intel_guc_send_mmio(guc, action, ARRAY_SIZE(action));
+	err = intel_guc_send_mmio(guc, action, ARRAY_SIZE(action), NULL, 0);
 	if (err)
 		DRM_ERROR("CT: register %s buffer failed; err=%d\n",
 			  guc_ct_buffer_type_to_str(type), err);
@@ -98,7 +133,7 @@ static int guc_action_deregister_ct_buffer(struct intel_guc *guc,
 	int err;
 
 	/* Can't use generic send(), CT deregistration must go over MMIO */
-	err = intel_guc_send_mmio(guc, action, ARRAY_SIZE(action));
+	err = intel_guc_send_mmio(guc, action, ARRAY_SIZE(action), NULL, 0);
 	if (err)
 		DRM_ERROR("CT: deregister %s buffer failed; owner=%d err=%d\n",
 			  guc_ct_buffer_type_to_str(type), owner, err);
@@ -156,7 +191,8 @@ static int ctch_init(struct intel_guc *guc,
 		err = PTR_ERR(blob);
 		goto err_vma;
 	}
-	DRM_DEBUG_DRIVER("CT: vma base=%#x\n", guc_ggtt_offset(ctch->vma));
+	CT_DEBUG_DRIVER("CT: vma base=%#x\n",
+			intel_guc_ggtt_offset(guc, ctch->vma));
 
 	/* store pointers to desc and cmds */
 	for (i = 0; i < ARRAY_SIZE(ctch->ctbs); i++) {
@@ -170,8 +206,8 @@ static int ctch_init(struct intel_guc *guc,
 err_vma:
 	i915_vma_unpin_and_release(&ctch->vma);
 err_out:
-	DRM_DEBUG_DRIVER("CT: channel %d initialization failed; err=%d\n",
-			 ctch->owner, err);
+	CT_DEBUG_DRIVER("CT: channel %d initialization failed; err=%d\n",
+			ctch->owner, err);
 	return err;
 }
 
@@ -191,8 +227,8 @@ static int ctch_open(struct intel_guc *guc,
 	int err;
 	int i;
 
-	DRM_DEBUG_DRIVER("CT: channel %d reopen=%s\n",
-			 ctch->owner, yesno(ctch_is_open(ctch)));
+	CT_DEBUG_DRIVER("CT: channel %d reopen=%s\n",
+			ctch->owner, yesno(ctch_is_open(ctch)));
 
 	if (!ctch->vma) {
 		err = ctch_init(guc, ctch);
@@ -202,7 +238,7 @@ static int ctch_open(struct intel_guc *guc,
 	}
 
 	/* vma should be already allocated and map'ed */
-	base = guc_ggtt_offset(ctch->vma);
+	base = intel_guc_ggtt_offset(guc, ctch->vma);
 
 	/* (re)initialize descriptors
 	 * cmds buffers are in the second half of the blob page
@@ -263,10 +299,29 @@ static u32 ctch_get_next_fence(struct intel_guc_ct_channel *ctch)
 	return ++ctch->next_fence;
 }
 
+/**
+ * DOC: CTB Host to GuC request
+ *
+ * Format of the CTB Host to GuC request message is as follows::
+ *
+ *      +------------+---------+---------+---------+---------+
+ *      |   msg[0]   |   [1]   |   [2]   |   ...   |  [n-1]  |
+ *      +------------+---------+---------+---------+---------+
+ *      |   MESSAGE  |       MESSAGE PAYLOAD                 |
+ *      +   HEADER   +---------+---------+---------+---------+
+ *      |            |    0    |    1    |   ...   |    n    |
+ *      +============+=========+=========+=========+=========+
+ *      |  len >= 1  |  FENCE  |     request specific data   |
+ *      +------+-----+---------+---------+---------+---------+
+ *
+ *                   ^-----------------len-------------------^
+ */
+
 static int ctb_write(struct intel_guc_ct_buffer *ctb,
 		     const u32 *action,
 		     u32 len /* in dwords */,
-		     u32 fence)
+		     u32 fence,
+		     bool want_response)
 {
 	struct guc_ct_buffer_desc *desc = ctb->desc;
 	u32 head = desc->head / 4;	/* in dwords */
@@ -295,15 +350,21 @@ static int ctb_write(struct intel_guc_ct_buffer *ctb,
 	if (unlikely(used + len + 1 >= size))
 		return -ENOSPC;
 
-	/* Write the message. The format is the following:
+	/*
+	 * Write the message. The format is the following:
 	 * DW0: header (including action code)
 	 * DW1: fence
 	 * DW2+: action data
 	 */
 	header = (len << GUC_CT_MSG_LEN_SHIFT) |
 		 (GUC_CT_MSG_WRITE_FENCE_TO_DESC) |
+		 (want_response ? GUC_CT_MSG_SEND_STATUS : 0) |
 		 (action[0] << GUC_CT_MSG_ACTION_SHIFT);
 
+	CT_DEBUG_DRIVER("CT: writing %*ph %*ph %*ph\n",
+			4, &header, 4, &fence,
+			4 * (len - 1), &action[1]);
+
 	cmds[tail] = header;
 	tail = (tail + 1) % size;
 
@@ -322,16 +383,25 @@ static int ctb_write(struct intel_guc_ct_buffer *ctb,
 	return 0;
 }
 
-/* Wait for the response from the GuC.
+/**
+ * wait_for_ctb_desc_update - Wait for the CT buffer descriptor update.
+ * @desc:	buffer descriptor
  * @fence:	response fence
  * @status:	placeholder for status
- * return:	0 response received (status is valid)
- *		-ETIMEDOUT no response within hardcoded timeout
- *		-EPROTO no response, ct buffer was in error
+ *
+ * Guc will update CT buffer descriptor with new fence and status
+ * after processing the command identified by the fence. Wait for
+ * specified fence and then read from the descriptor status of the
+ * command.
+ *
+ * Return:
+ * *	0 response received (status is valid)
+ * *	-ETIMEDOUT no response within hardcoded timeout
+ * *	-EPROTO no response, CT buffer is in error
  */
-static int wait_for_response(struct guc_ct_buffer_desc *desc,
-			     u32 fence,
-			     u32 *status)
+static int wait_for_ctb_desc_update(struct guc_ct_buffer_desc *desc,
+				    u32 fence,
+				    u32 *status)
 {
 	int err;
 
@@ -363,71 +433,440 @@ static int wait_for_response(struct guc_ct_buffer_desc *desc,
 	return err;
 }
 
-static int ctch_send(struct intel_guc *guc,
+/**
+ * wait_for_ct_request_update - Wait for CT request state update.
+ * @req:	pointer to pending request
+ * @status:	placeholder for status
+ *
+ * For each sent request, Guc shall send bac CT response message.
+ * Our message handler will update status of tracked request once
+ * response message with given fence is received. Wait here and
+ * check for valid response status value.
+ *
+ * Return:
+ * *	0 response received (status is valid)
+ * *	-ETIMEDOUT no response within hardcoded timeout
+ */
+static int wait_for_ct_request_update(struct ct_request *req, u32 *status)
+{
+	int err;
+
+	/*
+	 * Fast commands should complete in less than 10us, so sample quickly
+	 * up to that length of time, then switch to a slower sleep-wait loop.
+	 * No GuC command should ever take longer than 10ms.
+	 */
+#define done INTEL_GUC_MSG_IS_RESPONSE(READ_ONCE(req->status))
+	err = wait_for_us(done, 10);
+	if (err)
+		err = wait_for(done, 10);
+#undef done
+
+	if (unlikely(err))
+		DRM_ERROR("CT: fence %u err %d\n", req->fence, err);
+
+	*status = req->status;
+	return err;
+}
+
+static int ctch_send(struct intel_guc_ct *ct,
 		     struct intel_guc_ct_channel *ctch,
 		     const u32 *action,
 		     u32 len,
+		     u32 *response_buf,
+		     u32 response_buf_size,
 		     u32 *status)
 {
 	struct intel_guc_ct_buffer *ctb = &ctch->ctbs[CTB_SEND];
 	struct guc_ct_buffer_desc *desc = ctb->desc;
+	struct ct_request request;
+	unsigned long flags;
 	u32 fence;
 	int err;
 
 	GEM_BUG_ON(!ctch_is_open(ctch));
 	GEM_BUG_ON(!len);
 	GEM_BUG_ON(len & ~GUC_CT_MSG_LEN_MASK);
+	GEM_BUG_ON(!response_buf && response_buf_size);
 
 	fence = ctch_get_next_fence(ctch);
-	err = ctb_write(ctb, action, len, fence);
+	request.fence = fence;
+	request.status = 0;
+	request.response_len = response_buf_size;
+	request.response_buf = response_buf;
+
+	spin_lock_irqsave(&ct->lock, flags);
+	list_add_tail(&request.link, &ct->pending_requests);
+	spin_unlock_irqrestore(&ct->lock, flags);
+
+	err = ctb_write(ctb, action, len, fence, !!response_buf);
 	if (unlikely(err))
-		return err;
+		goto unlink;
 
-	intel_guc_notify(guc);
+	intel_guc_notify(ct_to_guc(ct));
 
-	err = wait_for_response(desc, fence, status);
+	if (response_buf)
+		err = wait_for_ct_request_update(&request, status);
+	else
+		err = wait_for_ctb_desc_update(desc, fence, status);
 	if (unlikely(err))
-		return err;
-	if (*status != INTEL_GUC_STATUS_SUCCESS)
-		return -EIO;
-	return 0;
+		goto unlink;
+
+	if (!INTEL_GUC_MSG_IS_RESPONSE_SUCCESS(*status)) {
+		err = -EIO;
+		goto unlink;
+	}
+
+	if (response_buf) {
+		/* There shall be no data in the status */
+		WARN_ON(INTEL_GUC_MSG_TO_DATA(request.status));
+		/* Return actual response len */
+		err = request.response_len;
+	} else {
+		/* There shall be no response payload */
+		WARN_ON(request.response_len);
+		/* Return data decoded from the status dword */
+		err = INTEL_GUC_MSG_TO_DATA(*status);
+	}
+
+unlink:
+	spin_lock_irqsave(&ct->lock, flags);
+	list_del(&request.link);
+	spin_unlock_irqrestore(&ct->lock, flags);
+
+	return err;
 }
 
 /*
  * Command Transport (CT) buffer based GuC send function.
  */
-static int intel_guc_send_ct(struct intel_guc *guc, const u32 *action, u32 len)
+static int intel_guc_send_ct(struct intel_guc *guc, const u32 *action, u32 len,
+			     u32 *response_buf, u32 response_buf_size)
 {
-	struct intel_guc_ct_channel *ctch = &guc->ct.host_channel;
+	struct intel_guc_ct *ct = &guc->ct;
+	struct intel_guc_ct_channel *ctch = &ct->host_channel;
 	u32 status = ~0; /* undefined */
-	int err;
+	int ret;
 
 	mutex_lock(&guc->send_mutex);
 
-	err = ctch_send(guc, ctch, action, len, &status);
-	if (unlikely(err)) {
+	ret = ctch_send(ct, ctch, action, len, response_buf, response_buf_size,
+			&status);
+	if (unlikely(ret < 0)) {
 		DRM_ERROR("CT: send action %#X failed; err=%d status=%#X\n",
-			  action[0], err, status);
+			  action[0], ret, status);
+	} else if (unlikely(ret)) {
+		CT_DEBUG_DRIVER("CT: send action %#x returned %d (%#x)\n",
+				action[0], ret, ret);
 	}
 
 	mutex_unlock(&guc->send_mutex);
-	return err;
+	return ret;
+}
+
+static inline unsigned int ct_header_get_len(u32 header)
+{
+	return (header >> GUC_CT_MSG_LEN_SHIFT) & GUC_CT_MSG_LEN_MASK;
+}
+
+static inline unsigned int ct_header_get_action(u32 header)
+{
+	return (header >> GUC_CT_MSG_ACTION_SHIFT) & GUC_CT_MSG_ACTION_MASK;
+}
+
+static inline bool ct_header_is_response(u32 header)
+{
+	return ct_header_get_action(header) == INTEL_GUC_ACTION_DEFAULT;
+}
+
+static int ctb_read(struct intel_guc_ct_buffer *ctb, u32 *data)
+{
+	struct guc_ct_buffer_desc *desc = ctb->desc;
+	u32 head = desc->head / 4;	/* in dwords */
+	u32 tail = desc->tail / 4;	/* in dwords */
+	u32 size = desc->size / 4;	/* in dwords */
+	u32 *cmds = ctb->cmds;
+	s32 available;			/* in dwords */
+	unsigned int len;
+	unsigned int i;
+
+	GEM_BUG_ON(desc->size % 4);
+	GEM_BUG_ON(desc->head % 4);
+	GEM_BUG_ON(desc->tail % 4);
+	GEM_BUG_ON(tail >= size);
+	GEM_BUG_ON(head >= size);
+
+	/* tail == head condition indicates empty */
+	available = tail - head;
+	if (unlikely(available == 0))
+		return -ENODATA;
+
+	/* beware of buffer wrap case */
+	if (unlikely(available < 0))
+		available += size;
+	CT_DEBUG_DRIVER("CT: available %d (%u:%u)\n", available, head, tail);
+	GEM_BUG_ON(available < 0);
+
+	data[0] = cmds[head];
+	head = (head + 1) % size;
+
+	/* message len with header */
+	len = ct_header_get_len(data[0]) + 1;
+	if (unlikely(len > (u32)available)) {
+		DRM_ERROR("CT: incomplete message %*ph %*ph %*ph\n",
+			  4, data,
+			  4 * (head + available - 1 > size ?
+			       size - head : available - 1), &cmds[head],
+			  4 * (head + available - 1 > size ?
+			       available - 1 - size + head : 0), &cmds[0]);
+		return -EPROTO;
+	}
+
+	for (i = 1; i < len; i++) {
+		data[i] = cmds[head];
+		head = (head + 1) % size;
+	}
+	CT_DEBUG_DRIVER("CT: received %*ph\n", 4 * len, data);
+
+	desc->head = head * 4;
+	return 0;
 }
 
 /**
- * Enable buffer based command transport
+ * DOC: CTB GuC to Host response
+ *
+ * Format of the CTB GuC to Host response message is as follows::
+ *
+ *      +------------+---------+---------+---------+---------+---------+
+ *      |   msg[0]   |   [1]   |   [2]   |   [3]   |   ...   |  [n-1]  |
+ *      +------------+---------+---------+---------+---------+---------+
+ *      |   MESSAGE  |       MESSAGE PAYLOAD                           |
+ *      +   HEADER   +---------+---------+---------+---------+---------+
+ *      |            |    0    |    1    |    2    |   ...   |    n    |
+ *      +============+=========+=========+=========+=========+=========+
+ *      |  len >= 2  |  FENCE  |  STATUS |   response specific data    |
+ *      +------+-----+---------+---------+---------+---------+---------+
+ *
+ *                   ^-----------------------len-----------------------^
+ */
+
+static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg)
+{
+	u32 header = msg[0];
+	u32 len = ct_header_get_len(header);
+	u32 msglen = len + 1; /* total message length including header */
+	u32 fence;
+	u32 status;
+	u32 datalen;
+	struct ct_request *req;
+	bool found = false;
+
+	GEM_BUG_ON(!ct_header_is_response(header));
+	GEM_BUG_ON(!in_irq());
+
+	/* Response payload shall at least include fence and status */
+	if (unlikely(len < 2)) {
+		DRM_ERROR("CT: corrupted response %*ph\n", 4 * msglen, msg);
+		return -EPROTO;
+	}
+
+	fence = msg[1];
+	status = msg[2];
+	datalen = len - 2;
+
+	/* Format of the status follows RESPONSE message */
+	if (unlikely(!INTEL_GUC_MSG_IS_RESPONSE(status))) {
+		DRM_ERROR("CT: corrupted response %*ph\n", 4 * msglen, msg);
+		return -EPROTO;
+	}
+
+	CT_DEBUG_DRIVER("CT: response fence %u status %#x\n", fence, status);
+
+	spin_lock(&ct->lock);
+	list_for_each_entry(req, &ct->pending_requests, link) {
+		if (unlikely(fence != req->fence)) {
+			CT_DEBUG_DRIVER("CT: request %u awaits response\n",
+					req->fence);
+			continue;
+		}
+		if (unlikely(datalen > req->response_len)) {
+			DRM_ERROR("CT: response %u too long %*ph\n",
+				  req->fence, 4 * msglen, msg);
+			datalen = 0;
+		}
+		if (datalen)
+			memcpy(req->response_buf, msg + 3, 4 * datalen);
+		req->response_len = datalen;
+		WRITE_ONCE(req->status, status);
+		found = true;
+		break;
+	}
+	spin_unlock(&ct->lock);
+
+	if (!found)
+		DRM_ERROR("CT: unsolicited response %*ph\n", 4 * msglen, msg);
+	return 0;
+}
+
+static void ct_process_request(struct intel_guc_ct *ct,
+			       u32 action, u32 len, const u32 *payload)
+{
+	struct intel_guc *guc = ct_to_guc(ct);
+
+	CT_DEBUG_DRIVER("CT: request %x %*ph\n", action, 4 * len, payload);
+
+	switch (action) {
+	case INTEL_GUC_ACTION_DEFAULT:
+		if (unlikely(len < 1))
+			goto fail_unexpected;
+		intel_guc_to_host_process_recv_msg(guc, *payload);
+		break;
+
+	default:
+fail_unexpected:
+		DRM_ERROR("CT: unexpected request %x %*ph\n",
+			  action, 4 * len, payload);
+		break;
+	}
+}
+
+static bool ct_process_incoming_requests(struct intel_guc_ct *ct)
+{
+	unsigned long flags;
+	struct ct_incoming_request *request;
+	u32 header;
+	u32 *payload;
+	bool done;
+
+	spin_lock_irqsave(&ct->lock, flags);
+	request = list_first_entry_or_null(&ct->incoming_requests,
+					   struct ct_incoming_request, link);
+	if (request)
+		list_del(&request->link);
+	done = !!list_empty(&ct->incoming_requests);
+	spin_unlock_irqrestore(&ct->lock, flags);
+
+	if (!request)
+		return true;
+
+	header = request->msg[0];
+	payload = &request->msg[1];
+	ct_process_request(ct,
+			   ct_header_get_action(header),
+			   ct_header_get_len(header),
+			   payload);
+
+	kfree(request);
+	return done;
+}
+
+static void ct_incoming_request_worker_func(struct work_struct *w)
+{
+	struct intel_guc_ct *ct = container_of(w, struct intel_guc_ct, worker);
+	bool done;
+
+	done = ct_process_incoming_requests(ct);
+	if (!done)
+		queue_work(system_unbound_wq, &ct->worker);
+}
+
+/**
+ * DOC: CTB GuC to Host request
+ *
+ * Format of the CTB GuC to Host request message is as follows::
+ *
+ *      +------------+---------+---------+---------+---------+---------+
+ *      |   msg[0]   |   [1]   |   [2]   |   [3]   |   ...   |  [n-1]  |
+ *      +------------+---------+---------+---------+---------+---------+
+ *      |   MESSAGE  |       MESSAGE PAYLOAD                           |
+ *      +   HEADER   +---------+---------+---------+---------+---------+
+ *      |            |    0    |    1    |    2    |   ...   |    n    |
+ *      +============+=========+=========+=========+=========+=========+
+ *      |     len    |            request specific data                |
+ *      +------+-----+---------+---------+---------+---------+---------+
+ *
+ *                   ^-----------------------len-----------------------^
+ */
+
+static int ct_handle_request(struct intel_guc_ct *ct, const u32 *msg)
+{
+	u32 header = msg[0];
+	u32 len = ct_header_get_len(header);
+	u32 msglen = len + 1; /* total message length including header */
+	struct ct_incoming_request *request;
+	unsigned long flags;
+
+	GEM_BUG_ON(ct_header_is_response(header));
+
+	request = kmalloc(sizeof(*request) + 4 * msglen, GFP_ATOMIC);
+	if (unlikely(!request)) {
+		DRM_ERROR("CT: dropping request %*ph\n", 4 * msglen, msg);
+		return 0; /* XXX: -ENOMEM ? */
+	}
+	memcpy(request->msg, msg, 4 * msglen);
+
+	spin_lock_irqsave(&ct->lock, flags);
+	list_add_tail(&request->link, &ct->incoming_requests);
+	spin_unlock_irqrestore(&ct->lock, flags);
+
+	queue_work(system_unbound_wq, &ct->worker);
+	return 0;
+}
+
+static void ct_process_host_channel(struct intel_guc_ct *ct)
+{
+	struct intel_guc_ct_channel *ctch = &ct->host_channel;
+	struct intel_guc_ct_buffer *ctb = &ctch->ctbs[CTB_RECV];
+	u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */
+	int err = 0;
+
+	if (!ctch_is_open(ctch))
+		return;
+
+	do {
+		err = ctb_read(ctb, msg);
+		if (err)
+			break;
+
+		if (ct_header_is_response(msg[0]))
+			err = ct_handle_response(ct, msg);
+		else
+			err = ct_handle_request(ct, msg);
+	} while (!err);
+
+	if (GEM_WARN_ON(err == -EPROTO)) {
+		DRM_ERROR("CT: corrupted message detected!\n");
+		ctb->desc->is_in_error = 1;
+	}
+}
+
+/*
+ * When we're communicating with the GuC over CT, GuC uses events
+ * to notify us about new messages being posted on the RECV buffer.
+ */
+static void intel_guc_to_host_event_handler_ct(struct intel_guc *guc)
+{
+	struct intel_guc_ct *ct = &guc->ct;
+
+	ct_process_host_channel(ct);
+}
+
+/**
+ * intel_guc_ct_enable - Enable buffer based command transport.
+ * @ct: pointer to CT struct
+ *
  * Shall only be called for platforms with HAS_GUC_CT.
- * @guc:	the guc
- * return:	0 on success
- *		non-zero on failure
+ *
+ * Return: 0 on success, a negative errno code on failure.
  */
-int intel_guc_enable_ct(struct intel_guc *guc)
+int intel_guc_ct_enable(struct intel_guc_ct *ct)
 {
-	struct drm_i915_private *dev_priv = guc_to_i915(guc);
-	struct intel_guc_ct_channel *ctch = &guc->ct.host_channel;
+	struct intel_guc *guc = ct_to_guc(ct);
+	struct drm_i915_private *i915 = guc_to_i915(guc);
+	struct intel_guc_ct_channel *ctch = &ct->host_channel;
 	int err;
 
-	GEM_BUG_ON(!HAS_GUC_CT(dev_priv));
+	GEM_BUG_ON(!HAS_GUC_CT(i915));
 
 	err = ctch_open(guc, ctch);
 	if (unlikely(err))
@@ -435,21 +874,24 @@ int intel_guc_enable_ct(struct intel_guc *guc)
 
 	/* Switch into cmd transport buffer based send() */
 	guc->send = intel_guc_send_ct;
+	guc->handler = intel_guc_to_host_event_handler_ct;
 	DRM_INFO("CT: %s\n", enableddisabled(true));
 	return 0;
 }
 
 /**
- * Disable buffer based command transport.
+ * intel_guc_ct_disable - Disable buffer based command transport.
+ * @ct: pointer to CT struct
+ *
  * Shall only be called for platforms with HAS_GUC_CT.
- * @guc: the guc
  */
-void intel_guc_disable_ct(struct intel_guc *guc)
+void intel_guc_ct_disable(struct intel_guc_ct *ct)
 {
-	struct drm_i915_private *dev_priv = guc_to_i915(guc);
-	struct intel_guc_ct_channel *ctch = &guc->ct.host_channel;
+	struct intel_guc *guc = ct_to_guc(ct);
+	struct drm_i915_private *i915 = guc_to_i915(guc);
+	struct intel_guc_ct_channel *ctch = &ct->host_channel;
 
-	GEM_BUG_ON(!HAS_GUC_CT(dev_priv));
+	GEM_BUG_ON(!HAS_GUC_CT(i915));
 
 	if (!ctch_is_open(ctch))
 		return;
@@ -458,5 +900,6 @@ void intel_guc_disable_ct(struct intel_guc *guc)
 
 	/* Disable send */
 	guc->send = intel_guc_send_nop;
+	guc->handler = intel_guc_to_host_event_handler_nop;
 	DRM_INFO("CT: %s\n", enableddisabled(false));
 }