[PATCH 2/4] drm/i915: read sink_count dpcd always

[Sivakumar Thulasimani <sivakumar.thulasimani@xxxxxxxxx>]

From: "Thulasimani,Sivakumar" <sivakumar.thulasimani@xxxxxxxxx>

This patch reads sink_count dpcd always and removes its
read operation based on values in downstream port dpcd.

SINK_COUNT dpcd is not dependent on DOWNSTREAM_PORT_PRESENT dpcd.
SINK_COUNT denotes if a display is attached, while
DOWNSTREAM_PORT_PRESET indicates how many ports are available
in the dongle where display can be attached. so it is possible
for sink count to change irrespective of value in downstream
port dpcd.

Here is a table of possible values and scenarios

sink_count      downstream_port
                present
0               0               no display is attached
0               1               dongle is connected without display
1               0               display connected directly
1               1               display connected through dongle

v2: moved out crtc enabled checks to prior patch(Jani)

Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@xxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_dp.c |   21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 76561e0..9e4e27d 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3898,6 +3898,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 	struct drm_device *dev = dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	uint8_t rev;
+	uint8_t reg;
 
 	if (intel_dp_dpcd_read_wake(&intel_dp->aux, 0x000, intel_dp->dpcd,
 				    sizeof(intel_dp->dpcd)) < 0)
@@ -3908,6 +3909,13 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 	if (intel_dp->dpcd[DP_DPCD_REV] == 0)
 		return false; /* DPCD not present */
 
+	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
+					    &reg, 1) < 0)
+			return false;
+
+	if (!DP_GET_SINK_COUNT(reg))
+		return false;
+
 	/* Check if the panel supports PSR */
 	memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
 	if (is_edp(intel_dp)) {
@@ -4427,19 +4435,6 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	if (!(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
 		return connector_status_connected;
 
-	/* If we're HPD-aware, SINK_COUNT changes dynamically */
-	if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11 &&
-	    intel_dp->downstream_ports[0] & DP_DS_PORT_HPD) {
-		uint8_t reg;
-
-		if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
-					    &reg, 1) < 0)
-			return connector_status_unknown;
-
-		return DP_GET_SINK_COUNT(reg) ? connector_status_connected
-					      : connector_status_disconnected;
-	}
-
 	/* If no HPD, poke DDC gently */
 	if (drm_probe_ddc(&intel_dp->aux.ddc))
 		return connector_status_connected;
-- 
1.7.9.5

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