[Intel-gfx] [PATCH] drm/i915: Don't fallback to ddc probe if downstream port is dummy

[Mika Kuoppala]

If branch device advertise dummy enough sink, bail out early
trusting to sink count instead of falling back to ddc probe
which is deemed to fail.

References: https://bugs.freedesktop.org/show_bug.cgi?id=60263
Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8c70a83..703767e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2786,9 +2786,15 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	if (!(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
 		return connector_status_connected;
 
+	/* Analog or other */
+#define DP_PORT_TYPE_DUMMY 0x2
+
 	/* If we're HPD-aware, SINK_COUNT changes dynamically */
 	hpd = !!(intel_dp->downstream_ports[0] & DP_DS_PORT_HPD);
-	if (hpd) {
+
+	/* ...and if the downstream port type is dummy enough
+	 * dont fall into ddc probe as it will fail */
+	if (hpd || dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_PORT_TYPE_DUMMY) {
 		uint8_t reg;
 		if (!intel_dp_aux_native_read_retry(intel_dp, DP_SINK_COUNT,
 						    &reg, 1))
-- 
1.7.9.5