[Intel-gfx] [PATCH v2 4/4] drm/i915/icl: Add fallback detection method for TypeC legacy ports

[Imre Deak]

Add a fallback detection method for TypeC legacy ports in case the
VBT port information used to detect normally such ports is
incorrect.

For the fallback method we use the TypeC legacy mode specific HPD
interrupt flag which should only be raised for a legacy port.

WARN if the VBT port info is incorrect.

In a case where we'd detect the port in a contradicting way both as a
legacy and also as a USB DP and/or TBT alternate port treat the port
as legacy (by also emitting a WARN from icl_update_tc_port_type).

v2:
- Repurpose the detection as a fallback method instead of using
  it only for the DP legacy case. By now we should normally use VBT to
  detect DP legacy ports as well.

Suggested-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: José Roberto de Souza <jose.souza at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com> (v1)
---
 drivers/gpu/drm/i915/intel_dp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index b2a3012478ca..d00af92cd089 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5220,8 +5220,14 @@ static bool icl_tc_port_connected(struct drm_i915_private *dev_priv,
 	bool is_legacy, is_typec, is_tbt;
 	u32 dpsp;
 
-	is_legacy = intel_dig_port->tc_legacy_port ||
-		I915_READ(SDEISR) & SDE_TC_HOTPLUG_ICP(tc_port);
+	/*
+	 * WARN if we got a legacy port HPD, but VBT didn't mark the port as
+	 * legacy. Treat the port as legacy from now on.
+	 */
+	if (WARN_ON(!intel_dig_port->tc_legacy_port &&
+		    I915_READ(SDEISR) & SDE_TC_HOTPLUG_ICP(tc_port)))
+		intel_dig_port->tc_legacy_port = true;
+	is_legacy = intel_dig_port->tc_legacy_port;
 
 	/*
 	 * The spec says we shouldn't be using the ISR bits for detecting
-- 
2.13.2