[PATCH 1/2] drm/i915/dp_mst: Fix forced link retrain handling in MST HPD IRQ handler

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

Handling of a forced link retraining debugfs request via the DP MST HPD
IRQ handler is incorrectly skipped, if the IRQ handler doesn't see any
HPD IRQs raised by the sink. Fix this by ensuring that the request is
always handled (in the Fixes: commit below by directly calling
intel_dp_check_link_state(), later by the same call moved to
intel_dp_handle_link_service_irq()).

Cc: Luca Coelho <luciano.coelho@intel.com>
Fixes: db4855d90363 ("drm/i915/dp_mst: Reuse intel_dp_check_link_state() in the HPD IRQ handler")
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index fbb5e2f9c2414..2ae030eda73ee 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5575,11 +5575,13 @@ static bool
 intel_dp_check_mst_status(struct intel_dp *intel_dp)
 {
 	struct intel_display *display = to_intel_display(intel_dp);
+	bool force_retrain = intel_dp->link.force_retrain;
 	bool reprobe_needed = false;
 
 	for (;;) {
 		u8 esi[4] = {};
 		u8 ack[4] = {};
+		bool new_irqs;
 
 		if (!intel_dp_get_sink_irq_esi(intel_dp, esi)) {
 			drm_dbg_kms(display->drm,
@@ -5595,20 +5597,28 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 
 		intel_dp_mst_hpd_irq(intel_dp, esi, ack);
 
-		if (mem_is_zero(ack, sizeof(ack)))
-			break;
+		new_irqs = !mem_is_zero(ack, sizeof(ack));
 
 		drm_WARN_ON(display->drm, ack[1] & ~INTEL_DP_DEVICE_SERVICE_IRQ_MASK_MST);
 		drm_WARN_ON(display->drm, ack[3] & ~INTEL_DP_LINK_SERVICE_IRQ_MASK_MST);
 
-		if (!intel_dp_ack_sink_irq_esi(intel_dp, ack))
+		if (new_irqs && !intel_dp_ack_sink_irq_esi(intel_dp, ack))
 			drm_dbg_kms(display->drm, "Failed to ack ESI\n");
 
 		if (ack[1] & (DP_DOWN_REP_MSG_RDY | DP_UP_REQ_MSG_RDY))
 			drm_dp_mst_hpd_irq_send_new_request(&intel_dp->mst.mgr);
 
+		if (force_retrain) {
+			/* Defer forced retraining to the regular link status check. */
+			ack[3] |= LINK_STATUS_CHANGED;
+			force_retrain = false;
+		}
+
 		if (intel_dp_handle_link_service_irq(intel_dp, ack[3]))
 			reprobe_needed = true;
+
+		if (!new_irqs)
+			break;
 	}
 
 	return !reprobe_needed;
-- 
2.49.1