drm/i915/guc: Merge communication_stop and communication_disable

The only difference from the GuC POV between guc_communication_stop and
guc_communication_disable is that the former can be called after GuC
has been reset. Instead of having two separate paths, we can just skip
the call into GuC in the disabling path and re-use that.

Note that by using the disable() path instead of the stop() one there
are two additional changes in SW side for the stop path:

- interrupts are now disabled before disabling the CT, which is ok
  because we do not want interrupts with CT disabled;
- guc_get_mmio_msg() is called in the stop case as well, which is ok
  because if there are errors before the reset we do want to record
  them.
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191217012316.13271-1-daniele.ceraolospurio@intel.com

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

@@ -241,12 +241,14 @@ static void ctch_disable(struct intel_guc *guc,
 
 	ctch->enabled = false;
 
+	if (intel_guc_is_running(guc)) {
 		guc_action_deregister_ct_buffer(guc,
 						ctch->owner,
 						INTEL_GUC_CT_BUFFER_TYPE_SEND);
 		guc_action_deregister_ct_buffer(guc,
 						ctch->owner,
 						INTEL_GUC_CT_BUFFER_TYPE_RECV);
+	}
 }
 
 static u32 ctch_get_next_fence(struct intel_guc_ct_channel *ctch)

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

@@ -81,11 +81,6 @@ void intel_guc_ct_fini(struct intel_guc_ct *ct);
 int intel_guc_ct_enable(struct intel_guc_ct *ct);
 void intel_guc_ct_disable(struct intel_guc_ct *ct);
 
-static inline void intel_guc_ct_stop(struct intel_guc_ct *ct)
-{
-	ct->host_channel.enabled = false;
-}
-
 int intel_guc_send_ct(struct intel_guc *guc, const u32 *action, u32 len,
 		      u32 *response_buf, u32 response_buf_size);
 void intel_guc_to_host_event_handler_ct(struct intel_guc *guc);

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

@@ -224,7 +224,7 @@ static int guc_enable_communication(struct intel_guc *guc)
 	return 0;
 }
 
-static void __guc_stop_communication(struct intel_guc *guc)
+static void guc_disable_communication(struct intel_guc *guc)
 {
 	/*
 	 * Events generated during or after CT disable are logged by guc in
@@ -237,20 +237,6 @@ static void __guc_stop_communication(struct intel_guc *guc)
 
 	guc->send = intel_guc_send_nop;
 	guc->handler = intel_guc_to_host_event_handler_nop;
-}
-
-static void guc_stop_communication(struct intel_guc *guc)
-{
-	intel_guc_ct_stop(&guc->ct);
-
-	__guc_stop_communication(guc);
-
-	DRM_INFO("GuC communication stopped\n");
-}
-
-static void guc_disable_communication(struct intel_guc *guc)
-{
-	__guc_stop_communication(guc);
 
 	intel_guc_ct_disable(&guc->ct);
 
@@ -556,7 +542,7 @@ void intel_uc_reset_prepare(struct intel_uc *uc)
 	if (!intel_guc_is_running(guc))
 		return;
 
-	guc_stop_communication(guc);
+	guc_disable_communication(guc);
 	__uc_sanitize(uc);
 }