On Tue, 14 Nov 2023, Ville Syrjala wrote:
> From: Ville Syrjälä
>
> 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: sta...@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
Fingers crossed.
Reviewed-by: Jani Nikula
> ---
> 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(_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(_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(_priv->drm,
> + "[ENCODER:%d:%s] VGA converter detected,
> disabling eDP\n",
> + encoder->base.base.id, encoder->base.name);
> + goto out_vdd_off;
> + }
> }
>
> mutex_lock(_priv->drm.mode_config.mutex);
--
Jani Nikula, Intel
