drm/i915: New lock to serialize the Host2GuC actions

With the addition of new Host2GuC actions related to GuC logging, there
is a need of a lock to serialize them, as they can execute concurrently
with each other and also with other existing actions.

v2: Use mutex in place of spinlock to serialize, as sleep can happen
    while waiting for the action's response from GuC. (Tvrtko)

v3: To conform to the general rules, acquire mutex before taking the
    forcewake. (Tvrtko)
Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drivers/gpu/drm/i915/i915_guc_submission.c

@@ -87,6 +87,7 @@ static int host2guc_action(struct intel_guc *guc, u32 *data, u32 len)
 	if (WARN_ON(len < 1 || len > 15))
 		return -EINVAL;
 
+	mutex_lock(&guc->action_lock);
 	intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
 
 	dev_priv->guc.action_count += 1;
@@ -125,6 +126,7 @@ static int host2guc_action(struct intel_guc *guc, u32 *data, u32 len)
 	dev_priv->guc.action_status = status;
 
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
+	mutex_unlock(&guc->action_lock);
 
 	return ret;
 }
@@ -1366,6 +1368,7 @@ int i915_guc_submission_init(struct drm_i915_private *dev_priv)
 
 	guc->ctx_pool_vma = vma;
 	ida_init(&guc->ctx_ids);
+	mutex_init(&guc->action_lock);
 	guc_log_create(guc);
 	guc_addon_create(guc);
 

drivers/gpu/drm/i915/intel_guc.h

@@ -157,6 +157,9 @@ struct intel_guc {
 
 	uint64_t submissions[I915_NUM_ENGINES];
 	uint32_t last_seqno[I915_NUM_ENGINES];
+
+	/* To serialize the Host2GuC actions */
+	struct mutex action_lock;
 };
 
 /* intel_guc_loader.c */