drm/i915/guc: Start protecting access to CTB descriptors

We want to stop using guc.send_mutex while sending CTB messages
so we have to start protecting access to CTB send descriptor.

For completeness protect also CTB receive descriptor.

Add spinlock to struct intel_guc_ct_buffer and start using it.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210603051630.2635-15-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c

@@ -89,6 +89,8 @@ static void ct_incoming_request_worker_func(struct work_struct *w);
  */
 void intel_guc_ct_init_early(struct intel_guc_ct *ct)
 {
+	spin_lock_init(&ct->ctbs.send.lock);
+	spin_lock_init(&ct->ctbs.recv.lock);
 	spin_lock_init(&ct->requests.lock);
 	INIT_LIST_HEAD(&ct->requests.pending);
 	INIT_LIST_HEAD(&ct->requests.incoming);
@@ -473,17 +475,22 @@ static int ct_send(struct intel_guc_ct *ct,
 	GEM_BUG_ON(len & ~GUC_CT_MSG_LEN_MASK);
 	GEM_BUG_ON(!response_buf && response_buf_size);
 
+	spin_lock_irqsave(&ct->ctbs.send.lock, flags);
+
 	fence = ct_get_next_fence(ct);
 	request.fence = fence;
 	request.status = 0;
 	request.response_len = response_buf_size;
 	request.response_buf = response_buf;
 
-	spin_lock_irqsave(&ct->requests.lock, flags);
+	spin_lock(&ct->requests.lock);
 	list_add_tail(&request.link, &ct->requests.pending);
-	spin_unlock_irqrestore(&ct->requests.lock, flags);
+	spin_unlock(&ct->requests.lock);
 
 	err = ct_write(ct, action, len, fence);
+
+	spin_unlock_irqrestore(&ct->ctbs.send.lock, flags);
+
 	if (unlikely(err))
 		goto unlink;
 
@@ -819,6 +826,7 @@ static int ct_handle_request(struct intel_guc_ct *ct, const u32 *msg)
 void intel_guc_ct_event_handler(struct intel_guc_ct *ct)
 {
 	u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */
+	unsigned long flags;
 	int err = 0;
 
 	if (unlikely(!ct->enabled)) {
@@ -827,7 +835,9 @@ void intel_guc_ct_event_handler(struct intel_guc_ct *ct)
 	}
 
 	do {
+		spin_lock_irqsave(&ct->ctbs.recv.lock, flags);
 		err = ct_read(ct, msg);
+		spin_unlock_irqrestore(&ct->ctbs.recv.lock, flags);
 		if (err)
 			break;
 

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h

@@ -27,11 +27,13 @@ struct intel_guc;
  * record (command transport buffer descriptor) and the actual buffer which
  * holds the commands.
  *
+ * @lock: protects access to the commands buffer and buffer descriptor
  * @desc: pointer to the buffer descriptor
  * @cmds: pointer to the commands buffer
  * @size: size of the commands buffer
  */
 struct intel_guc_ct_buffer {
+	spinlock_t lock;
 	struct guc_ct_buffer_desc *desc;
 	u32 *cmds;
 	u32 size;