[PATCH 11/23] drm/i915: Handle the TCCOLD power-down event

[Imre Deak]

Based on a recent BSpec update (Index/21750) we must handle the TCCOLD
event associated with the DP-alt mode. We can detect this event by
reading an invalid all-1s value from FIA registers.

After detecting TCCOLD we will:
- fall back to TBT-alt mode when attempting to switch to DP-alt mode
- conclude that nothing is connected during live status detection
- WARN when already in unsafe mode, since then TCCOLD is unexpected

Cc: José Roberto de Souza <jose.souza at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/intel_tc.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_tc.c b/drivers/gpu/drm/i915/intel_tc.c
index 84e0c06877ec..d91381c0e87d 100644
--- a/drivers/gpu/drm/i915/intel_tc.c
+++ b/drivers/gpu/drm/i915/intel_tc.c
@@ -49,6 +49,8 @@ u32 intel_tc_port_get_lane_info(struct intel_digital_port *dig_port)
 	enum tc_port tc_port = intel_port_to_tc(dev_priv, dig_port->base.port);
 	u32 lane_info = I915_READ(PORT_TX_DFLEXDPSP);
 
+	WARN_ON(lane_info == -1);
+
 	return (lane_info & DP_LANE_ASSIGNMENT_MASK(tc_port)) >>
 	       DP_LANE_ASSIGNMENT_SHIFT(tc_port);
 }
@@ -107,6 +109,12 @@ static u32 tc_port_live_status_mask(struct intel_digital_port *dig_port)
 	u32 val = I915_READ(PORT_TX_DFLEXDPSP);
 	u32 mask = 0;
 
+	if (val == -1) {
+		DRM_DEBUG_DRIVER("Port %s: PHY in TCCOLD, nothing connected\n",
+				 tc_port_name(dev_priv, tc_port));
+		return mask;
+	}
+
 	if (val & TC_LIVE_STATE_TBT(tc_port))
 		mask |= BIT(TC_PORT_TBT_ALT);
 	if (val & TC_LIVE_STATE_TC(tc_port))
@@ -131,13 +139,21 @@ static bool icl_tc_phy_status_complete(struct intel_digital_port *dig_port)
 	       DP_PHY_MODE_STATUS_COMPLETED(tc_port);
 }
 
-static void icl_tc_phy_set_safe_mode(struct intel_digital_port *dig_port,
+static bool icl_tc_phy_set_safe_mode(struct intel_digital_port *dig_port,
 				     bool enable)
 {
 	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
 	enum tc_port tc_port = intel_port_to_tc(dev_priv, dig_port->base.port);
 	u32 val = I915_READ(PORT_TX_DFLEXDPCSSS);
 
+	if (val == -1) {
+		DRM_DEBUG_DRIVER("Port %s: PHY in TCCOLD, can't set safe-mode to %s\n",
+				 tc_port_name(dev_priv, tc_port),
+				 enableddisabled(enable));
+
+		return false;
+	}
+
 	val &= ~DP_PHY_MODE_STATUS_NOT_SAFE(tc_port);
 	if (!enable)
 		val |= DP_PHY_MODE_STATUS_NOT_SAFE(tc_port);
@@ -147,6 +163,8 @@ static void icl_tc_phy_set_safe_mode(struct intel_digital_port *dig_port,
 	if (enable && wait_for(!icl_tc_phy_status_complete(dig_port), 10))
 		DRM_DEBUG_DRIVER("Port %s: PHY complete clear timed out\n",
 				 tc_port_name(dev_priv, tc_port));
+
+	return true;
 }
 
 /*
@@ -187,7 +205,8 @@ static bool icl_tc_phy_connect(struct intel_digital_port *dig_port)
 		return false;
 	}
 
-	icl_tc_phy_set_safe_mode(dig_port, false);
+	if (!icl_tc_phy_set_safe_mode(dig_port, false))
+		return false;
 
 	if (dig_port->tc_mode == TC_PORT_LEGACY)
 		return true;
-- 
2.17.1