drm/i915/guc: Prepare to process incoming requests from CT

Requests are read from CT in the irq handler, but actual processing
will be done in the work thread. Processing of specific actions will
be added in the upcoming patches.

v2: don't use GEM_BUG_ON (Chris)
    don't kmalloc too large buffer (Michal)
v3: rebased
v4: don't name it 'dispatch' (Michel) and fix checkpatch
    add some documentation (Michal)

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180326194829.58836-10-michal.wajdeczko@intel.com

drivers/gpu/drm/i915/intel_guc_ct.c

@@ -32,10 +32,17 @@ struct ct_request {
 	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
@@ -47,6 +54,8 @@ void intel_guc_ct_init_early(struct intel_guc_ct *ct)
 
 	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)
@@ -682,13 +691,97 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg)
 	return 0;
 }
 
+static void ct_process_request(struct intel_guc_ct *ct,
+			       u32 action, u32 len, const u32 *payload)
+{
+	switch (action) {
+	default:
+		DRM_ERROR("CT: unexpected request %x %*phn\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));
 
-	/* XXX */
+	request = kmalloc(sizeof(*request) + 4 * msglen, GFP_ATOMIC);
+	if (unlikely(!request)) {
+		DRM_ERROR("CT: dropping request %*phn\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;
 }
 

drivers/gpu/drm/i915/intel_guc_ct.h

@@ -81,6 +81,12 @@ struct intel_guc_ct {
 
 	/** @pending_requests: list of requests waiting for response */
 	struct list_head pending_requests;
+
+	/** @incoming_requests: list of incoming requests */
+	struct list_head incoming_requests;
+
+	/** @worker: worker for handling incoming requests */
+	struct work_struct worker;
 };
 
 void intel_guc_ct_init_early(struct intel_guc_ct *ct);