Some eDP sinks, especially fixed-format eDP-to-HDMI bridge chips with no downstream AUX-capable panel behind them, do not report a non-zero DP_SINK_COUNT even though they participate normally in DPCD capability exchange and link training.
Treating sink_count == 0 as a permanent disconnect is valid for external DisplayPort, but it breaks eDP probe/enable paths in msm_dp_display_prepare_link(). Use the same eDP exemption as drm_dp_read_sink_count_cap() for the raw sink_count checks in this driver, via a small shared helper, so valid eDP outputs are not rejected as disconnected just because the downstream sink does not expose a usable DP_SINK_COUNT. Tested on a Qualcomm QCS6490-based board driving a fixed-format eDP-to-HDMI bridge IC (chrontel,ch7218a). Signed-off-by: Vivek Kumar <[email protected]> --- drivers/gpu/drm/msm/dp/dp_aux.c | 8 ++++++++ drivers/gpu/drm/msm/dp/dp_aux.h | 1 + drivers/gpu/drm/msm/dp/dp_link.c | 10 ++++++++++ 3 files changed, 19 insertions(+) diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c index 3825a2fb48e2..3b5a4da93122 100644 --- a/drivers/gpu/drm/msm/dp/dp_aux.c +++ b/drivers/gpu/drm/msm/dp/dp_aux.c @@ -679,6 +679,14 @@ u32 msm_dp_aux_is_link_connected(struct drm_dp_aux *msm_dp_aux) return status; } +bool msm_dp_aux_is_edp(struct drm_dp_aux *msm_dp_aux) +{ + struct msm_dp_aux_private *aux = + container_of(msm_dp_aux, struct msm_dp_aux_private, msm_dp_aux); + + return aux->is_edp; +} + struct drm_dp_aux *msm_dp_aux_get(struct device *dev, struct phy *phy, bool is_edp, diff --git a/drivers/gpu/drm/msm/dp/dp_aux.h b/drivers/gpu/drm/msm/dp/dp_aux.h index 4be02e8b4d0b..9ab401c8526f 100644 --- a/drivers/gpu/drm/msm/dp/dp_aux.h +++ b/drivers/gpu/drm/msm/dp/dp_aux.h @@ -22,6 +22,7 @@ void msm_dp_aux_hpd_intr_enable(struct drm_dp_aux *msm_dp_aux); void msm_dp_aux_hpd_intr_disable(struct drm_dp_aux *msm_dp_aux); u32 msm_dp_aux_get_hpd_intr_status(struct drm_dp_aux *msm_dp_aux); u32 msm_dp_aux_is_link_connected(struct drm_dp_aux *msm_dp_aux); +bool msm_dp_aux_is_edp(struct drm_dp_aux *msm_dp_aux); struct phy; struct drm_dp_aux *msm_dp_aux_get(struct device *dev, diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c index 34a91e194a12..bf08b5b18097 100644 --- a/drivers/gpu/drm/msm/dp/dp_link.c +++ b/drivers/gpu/drm/msm/dp/dp_link.c @@ -725,6 +725,16 @@ static int msm_dp_link_parse_sink_status_field(struct msm_dp_link_private *link) DRM_ERROR("DP parse sink count failed\n"); return ret; } + + /* + * Some eDP sinks do not report a valid sink count, even though they + * otherwise participate in link training and DPCD capability exchange. + * Treat a zero raw count as a valid non-zero placeholder so we do not + * misclassify the link as disconnected on eDP. + */ + if (msm_dp_aux_is_edp(link->aux) && ret == 0) + ret = 1; + link->msm_dp_link.sink_count = ret; ret = drm_dp_dpcd_read_link_status(link->aux, -- 2.55.0
