drm/i915/guc: handle GuC messages received with CTB disabled

There is a very small chance of triggering a log flush event when
enabling or disabling CT buffers. Events triggered while CT buffers
are disabled are logged in the SCRATCH_15 register using the same bits
used in the CT message payload. Since our communication channel with
GuC is turned off, we can save the message and handle it after we turn
it back on.
GuC should be idle and not generate more events in the meantime because
we're not talking to it.

v2: clear the mmio register on stop_communication as well (Chris)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190621182123.31368-2-daniele.ceraolospurio@intel.com

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index 08c906abdfa2..d6a75bc3d7f4 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -88,6 +88,9 @@ struct intel_guc {
 		enum forcewake_domains fw_domains;
 	} send_regs;
 
+	/* Store msg (e.g. log flush) that we see while CTBs are disabled */
+	u32 mmio_msg;
+
 	/* To serialize the intel_guc_send actions */
 	struct mutex send_mutex;
 
@@ -181,6 +184,8 @@ static inline bool intel_guc_is_loaded(struct intel_guc *guc)
 static inline int intel_guc_sanitize(struct intel_guc *guc)
 {
 	intel_uc_fw_sanitize(&guc->fw);
+	guc->mmio_msg = 0;
+
 	return 0;
 }