workaround link training problems on s3 resume with alder lake

The firmware from multiple lenovo alder lake machines claim there are
two eDP ports in the video bios table (VBT).

Which results in link training problems on resume from S3 with the
screen continually turning on and off.  Forcing port B to not be
recognised as eDP works around this.  I believe port A is the normal eDP
port.

https://gitlab.freedesktop.org/drm/intel/-/issues/5531
https://gitlab.freedesktop.org/drm/intel/-/issues/4950

diff --git a/sys/dev/pci/drm/i915/display/intel_bios.c b/sys/dev/pci/drm/i915/display/intel_bios.c
index b1fd568..eb3c1cc 100644 (file)
--- a/sys/dev/pci/drm/i915/display/intel_bios.c
+++ b/sys/dev/pci/drm/i915/display/intel_bios.c
@@ -2664,6 +2664,17 @@ bool intel_bios_is_port_edp(struct drm_i915_private *i915, enum port port)
                [PORT_F] = DVO_PORT_DPF,
        };
 
+       /*
+        * XXX on T14 Gen 3 resume
+        * [drm] AUX A/DDI A/PHY A: timeout (status 0x7d4003ff)
+        * [drm] AUX A/DDI A/PHY A: Too many retries, giving up. First error: -60
+        * intel_edp_init_source_oui *ERROR* [drm] *ERROR* Failed to write source OUI
+        * intel_dp_link_training_clock_recovery *ERROR* [drm] *ERROR* failed to enable link training
+        * https://gitlab.freedesktop.org/drm/intel/-/issues/5531
+        */
+       if (IS_ALDERLAKE_P(i915) && port == PORT_B)
+               return false;
+
        if (HAS_DDI(i915)) {
                const struct intel_bios_encoder_data *devdata;