On Tue, 14 Nov 2023, Ville Syrjala ville.syrjala@linux.intel.com wrote:

From: Ville Syrjälä ville.syrjala@linux.intel.com

Unfortunately even the HPD based detection added in commit cfe5bdfb27fa ("drm/i915: Check HPD live state during eDP probe") fails to detect that the VBT's eDP/DDI-A is a ghost on Asus B360M-A (CFL+CNP). On that board eDP/DDI-A has its HPD asserted despite nothing being actually connected there :( The straps/fuses also indicate that the eDP port is present.

So if one boots with a VGA monitor connected the eDP probe will mistake the DP->VGA converter hooked to DDI-E for an eDP panel on DDI-A.

As a last resort check what kind of DP device we've detected, and if it looks like a DP->VGA converter then conclude that the eDP port should be ignored.

Cc: stable@vger.kernel.org Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9636 Fixes: cfe5bdfb27fa ("drm/i915: Check HPD live state during eDP probe") Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com

Fingers crossed.

Reviewed-by: Jani Nikula jani.nikula@intel.com

---

drivers/gpu/drm/i915/display/intel_dp.c | 28 +++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 54bd0bffa9f0..14ee05fabd05 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -6277,8 +6277,7 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp, * (eg. Acer Chromebook C710), so we'll check it only if multiple * ports are attempting to use the same AUX CH, according to VBT. */

• if (intel_bios_dp_has_shared_aux_ch(encoder->devdata) &&

•    !intel_digital_port_connected(encoder)) {
  

• if (intel_bios_dp_has_shared_aux_ch(encoder->devdata)) { /*
  • If this fails, presume the DPCD answer came
  • from some other port using the same AUX CH.

@@ -6286,10 +6285,27 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp, * FIXME maybe cleaner to check this before the * DPCD read? Would need sort out the VDD handling... */

• drm_info(&dev_priv->drm,
  

• 	 "[ENCODER:%d:%s] HPD is down, disabling eDP\n",
  

• 	 encoder->base.base.id, encoder->base.name);
  

• goto out_vdd_off;
  

• if (!intel_digital_port_connected(encoder)) {
  

• 	drm_info(&dev_priv->drm,
  

• 		 "[ENCODER:%d:%s] HPD is down, disabling eDP\n",
  

• 		 encoder->base.base.id, encoder->base.name);
  

• 	goto out_vdd_off;
  

• }
  

• /*
  

•  * Unfortunately even the HPD based detection fails on
  

•  * eg. Asus B360M-A (CFL+CNP), so as a last resort fall
  

•  * back to checking for a VGA branch device. Only do this
  

•  * on known affected platforms to minimize false positives.
  

•  */
  

• if (DISPLAY_VER(dev_priv) == 9 && drm_dp_is_branch(intel_dp->dpcd) &&
  

•     (intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_TYPE_MASK) ==
  

•     DP_DWN_STRM_PORT_TYPE_ANALOG) {
  

• 	drm_info(&dev_priv->drm,
  

• 		 "[ENCODER:%d:%s] VGA converter detected, disabling eDP\n",
  

• 		 encoder->base.base.id, encoder->base.name);
  

• 	goto out_vdd_off;
  

• }
  

  }

mutex_lock(&dev_priv->drm.mode_config.mutex);