[PATCH v2] drm: Print some debug/error info during DP dual mode detect

[Imre Deak]

There's at least one LSPCON device that occasionally returns an unexpected
adaptor ID which leads to a failed detect. Print some debug info to help
debugging this and future cases. Also print an error for an unexpected
adaptor ID, so users can report it.

v2:
- s/adapter/adaptor/ and add code comment about incorrect type 1 adaptor
  IDs. (Ville)

Cc: dri-devel at lists.freedesktop.org
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_dp_dual_mode_helper.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c 
b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
index 488355b..e025639 100644
--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
@@ -142,6 +142,11 @@ static bool is_hdmi_adaptor(const char 
hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
                      sizeof(dp_dual_mode_hdmi_id)) == 0;
 }

+static bool is_type1_adaptor(uint8_t adaptor_id)
+{
+       return adaptor_id == 0 || adaptor_id == 0xff;
+}
+
 static bool is_type2_adaptor(uint8_t adaptor_id)
 {
        return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
@@ -193,6 +198,8 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct 
i2c_adapter *adapter)
         */
        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
                                    hdmi_id, sizeof(hdmi_id));
+       DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
+                     ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
        if (ret)
                return DRM_DP_DUAL_MODE_UNKNOWN;

@@ -210,6 +217,8 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct 
i2c_adapter *adapter)
         */
        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
                                    &adaptor_id, sizeof(adaptor_id));
+       DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
+                     adaptor_id, ret);
        if (ret == 0) {
                if (is_lspcon_adaptor(hdmi_id, adaptor_id))
                        return DRM_DP_DUAL_MODE_LSPCON;
@@ -219,6 +228,15 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct 
i2c_adapter *adapter)
                        else
                                return DRM_DP_DUAL_MODE_TYPE2_DVI;
                }
+               /*
+                * If neither a proper type 1 ID nor a broken type 1 adaptor
+                * as described above, assume type 1, but let the user know
+                * that we may have misdetected the type.
+                */
+               if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
+                       DRM_ERROR("Unexpected DP dual mode adaptor ID %02x\n",
+                                 adaptor_id);
+
        }

        if (is_hdmi_adaptor(hdmi_id))
-- 
2.5.0