[PATCH] drm/i915/icl+: Prevent using non-TypeC AUX channels on TypeC ports

[Imre Deak]

Using an AUX channel which by default belongs to a non-TypeC PHY won't
work on a TypeC PHY, since - as a side-effect besides providing an AUX
channel - the AUX channel power well affects power manangement specific
to the TypeC subsystem. Using a TypeC AUX channel on a non-TypeC PHY
would probably also cause problems, so for simplicity prevent both.

This fixes at least an ICL-Y machine in CI, which has a buggy VBT
setting AUX-B as an alternative channel for port C.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_bios.c | 30 +++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index 839124647202..ab360e31e351 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -1543,6 +1543,8 @@ static void sanitize_aux_ch(struct drm_i915_private *dev_priv,
 {
 	struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
 	enum port p;
+	bool aux_is_tc;
+	bool phy_is_tc;
 
 	if (!info->alternate_aux_channel)
 		return;
@@ -1571,6 +1573,34 @@ static void sanitize_aux_ch(struct drm_i915_private *dev_priv,
 
 		info->supports_dp = false;
 		info->alternate_aux_channel = 0;
+
+		return;
+	}
+
+	p = (enum port)info->alternate_aux_channel;
+	aux_is_tc = intel_phy_is_tc(dev_priv,
+				    intel_port_to_phy(dev_priv, p));
+	phy_is_tc = intel_phy_is_tc(dev_priv,
+				    intel_port_to_phy(dev_priv, port));
+	if (aux_is_tc != phy_is_tc) {
+		/*
+		 * Using an AUX channel which by default belongs to a TypeC
+		 * PHY can't be used for non-TypeC PHYs and vice-versa. The
+		 * reason is that TypeC AUX power wells can only be enabled in
+		 * the current TypeC mode of the PHY and have an effect on power
+		 * management specific to the TypeC subsystem.
+		 */
+		drm_dbg_kms(&dev_priv->drm,
+			    "port %c on a %s PHY trying to use the %s AUX CH 0x%x, "
+			    "disabling port %c DP support\n",
+			    port_name(port),
+			    phy_is_tc ? "TypeC" : "non-TypeC",
+			    aux_is_tc ? "TypeC" : "non-TypeC",
+			    info->alternate_aux_channel,
+			    port_name(port));
+
+		info->supports_dp = false;
+		info->alternate_aux_channel = 0;
 	}
 }
 
-- 
2.20.1