drm/dp: Add helpers to identify downstream facing port types

Add a few helpers to let us better identify which kind of DFP
we're dealing with.

v2: Use Returns: for kdoc (Lyude)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904115354.25336-7-ville.syrjala@linux.intel.com
Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index c21bbfc3d71474a9d644afe66594aec96df30b36..56a3ba1477133ab8bd2491f8fbbd2d940b333c53 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -363,6 +363,66 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
 }
 EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
 
+static bool is_edid_digital_input_dp(const struct edid *edid)
+{
+       return edid && edid->revision >= 4 &&
+               edid->input & DRM_EDID_INPUT_DIGITAL &&
+               (edid->input & DRM_EDID_DIGITAL_TYPE_MASK) == DRM_EDID_DIGITAL_TYPE_DP;
+}
+
+/**
+ * drm_dp_downstream_is_type() - is the downstream facing port of certain type?
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ *
+ * Caveat: Only works with DPCD 1.1+ port caps.
+ *
+ * Returns: whether the downstream facing port matches the type.
+ */
+bool drm_dp_downstream_is_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+                              const u8 port_cap[4], u8 type)
+{
+       return drm_dp_is_branch(dpcd) &&
+               dpcd[DP_DPCD_REV] >= 0x11 &&
+               (port_cap[0] & DP_DS_PORT_TYPE_MASK) == type;
+}
+EXPORT_SYMBOL(drm_dp_downstream_is_type);
+
+/**
+ * drm_dp_downstream_is_tmds() - is the downstream facing port TMDS?
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ * @edid: EDID
+ *
+ * Returns: whether the downstream facing port is TMDS (HDMI/DVI).
+ */
+bool drm_dp_downstream_is_tmds(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+                              const u8 port_cap[4],
+                              const struct edid *edid)
+{
+       if (dpcd[DP_DPCD_REV] < 0x11) {
+               switch (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_TYPE_MASK) {
+               case DP_DWN_STRM_PORT_TYPE_TMDS:
+                       return true;
+               default:
+                       return false;
+               }
+       }
+
+       switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
+       case DP_DS_PORT_TYPE_DP_DUALMODE:
+               if (is_edid_digital_input_dp(edid))
+                       return false;
+               fallthrough;
+       case DP_DS_PORT_TYPE_DVI:
+       case DP_DS_PORT_TYPE_HDMI:
+               return true;
+       default:
+               return false;
+       }
+}
+EXPORT_SYMBOL(drm_dp_downstream_is_tmds);
+
 /**
  * drm_dp_send_real_edid_checksum() - send back real edid checksum value
  * @aux: DisplayPort AUX channel

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 86461a40066b2cb9a042aebc4b530d07f162b34c..4f946826dfce3bd131d875e0e6d286b0c09614d7 100644 (file)
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1638,6 +1638,11 @@ bool drm_dp_send_real_edid_checksum(struct drm_dp_aux *aux,
 int drm_dp_read_downstream_info(struct drm_dp_aux *aux,
                                const u8 dpcd[DP_RECEIVER_CAP_SIZE],
                                u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS]);
+bool drm_dp_downstream_is_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+                              const u8 port_cap[4], u8 type);
+bool drm_dp_downstream_is_tmds(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+                              const u8 port_cap[4],
+                              const struct edid *edid);
 int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
                                const u8 port_cap[4]);
 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],