[PATCH 06/20] drm/i915/dp: Handle the DOWNSTREAM_PORT_STATUS_CHANGED event

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

From: Imre Deak <imre.deak@gmail.com>

Handle the DOWNSTREAM_PORT_STATUS_CHANGED event a branch device can use
to indicate the state change of a DFP connector on the branch device.
The event is signaled in the DP_LANE_ALIGN_STATUS_UPDATED DPCD register
setting a clear-on-read flag and triggering an HPD IRQ. Accordingly keep
a cached version of the flag, updating it whenever
DP_LANE_ALIGN_STATUS_UPDATED is read. Schedule a full connector
detection from the HPD IRQ handler if the cached flag is set and clear
the cached flag at the start of detection.

Signed-off-by: Imre Deak <imre.deak@gmail.com>
---
 .../gpu/drm/i915/display/intel_display_types.h   |  1 +
 drivers/gpu/drm/i915/display/intel_dp.c          | 16 +++++++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 30c7315fc25e3..039a65a6b68d4 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1669,6 +1669,7 @@ struct intel_dp {
 	int link_rate;
 	u8 lane_count;
 	u8 sink_count;
+	bool downstream_port_changed;
 	bool needs_modeset_retry;
 	bool use_max_params;
 	u8 dpcd[DP_RECEIVER_CAP_SIZE];
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index c2eadfa060c2d..7d8421649be0d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5164,7 +5164,14 @@ intel_dp_read_link_status(struct intel_dp *intel_dp, u8 link_status[DP_LINK_STAT
 		ret = drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
 						       link_status) == 0;
 
-	return ret;
+	if (!ret)
+		return false;
+
+	if (link_status[DP_LANE_ALIGN_STATUS_UPDATED - DP_LANE0_1_STATUS] &
+	    DP_DOWNSTREAM_PORT_STATUS_CHANGED)
+		WRITE_ONCE(intel_dp->downstream_port_changed, true);
+
+	return true;
 }
 
 static bool
@@ -5484,6 +5491,11 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
 
 	intel_dp_check_link_state(intel_dp);
 
+	if (READ_ONCE(intel_dp->downstream_port_changed)) {
+		WRITE_ONCE(intel_dp->downstream_port_changed, false);
+		reprobe_needed = true;
+	}
+
 	intel_psr_short_pulse(intel_dp);
 
 	if (intel_alpm_get_error(intel_dp)) {
@@ -5509,6 +5521,8 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	if (drm_WARN_ON(display->drm, intel_dp_is_edp(intel_dp)))
 		return connector_status_connected;
 
+	WRITE_ONCE(intel_dp->downstream_port_changed, false);
+
 	intel_lspcon_resume(dig_port);
 
 	if (!intel_dp_get_dpcd(intel_dp))
-- 
2.44.2