[PATCH v3 19/20] drm/i915/dp: Ack only the handled device service IRQs

[Imre Deak <imre.deak@intel.com>]

Only those IRQs should be acked that are handled, however for SST all
IRQs triggered by the sink are acked. This can be a problem for flags
that are reserved/reading zero at a given moment, but become used for
some purpose - with a side-effect if set - in a future DPCD revision.

Fix the above by acking only those device service IRQs that will be
handled. While at it add asserts that only the known/acked device
service IRQs are handled both in the MST and SST case.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 05e3071f33e27..866aeeb8f4614 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4916,6 +4916,14 @@ intel_dp_mst_disconnect(struct intel_dp *intel_dp)
 	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst.mgr, intel_dp->is_mst);
 }
 
+#define INTEL_DP_DEVICE_SERVICE_IRQ_MASK_SST	(DP_AUTOMATED_TEST_REQUEST | \
+						 DP_CP_IRQ | \
+						 DP_SINK_SPECIFIC_IRQ)
+
+#define INTEL_DP_DEVICE_SERVICE_IRQ_MASK_MST	(DP_CP_IRQ | \
+						 DP_DOWN_REP_MSG_RDY | \
+						 DP_UP_REQ_MSG_RDY)
+
 static bool
 intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *esi)
 {
@@ -5013,6 +5021,8 @@ static bool intel_dp_get_and_ack_sink_irq_esi_sst(struct intel_dp *intel_dp, u8
 		    encoder->base.base.id, encoder->base.name,
 		    esi);
 
+	esi[1] &= INTEL_DP_DEVICE_SERVICE_IRQ_MASK_SST;
+
 	if (mem_is_zero(&esi[1], 3))
 		return true;
 
@@ -5557,6 +5567,8 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 		if (mem_is_zero(ack, sizeof(ack)))
 			break;
 
+		drm_WARN_ON(display->drm, ack[1] & ~INTEL_DP_DEVICE_SERVICE_IRQ_MASK_MST);
+
 		if (!intel_dp_ack_sink_irq_esi(intel_dp, ack))
 			drm_dbg_kms(display->drm, "Failed to ack ESI\n");
 
@@ -5841,6 +5853,8 @@ static void intel_dp_handle_device_service_irq(struct intel_dp *intel_dp, u8 irq
 {
 	struct intel_display *display = to_intel_display(intel_dp);
 
+	drm_WARN_ON(display->drm, irq_mask & ~INTEL_DP_DEVICE_SERVICE_IRQ_MASK_SST);
+
 	if (irq_mask & DP_AUTOMATED_TEST_REQUEST)
 		intel_dp_test_request(intel_dp);
 
-- 
2.49.1