This feature is useful for analog connections without EDID:
- Really old monitors with a VGA connector
- Cheap DVI/VGA adapters that don't connect DDC pins
When a connection is established through DAC load detection,
the driver is supposed to fill in the supported modes for the
display, which we already do in amdgpu_dm_connector_get_modes.
Signed-off-by: Timur Kristóf <timur.kris...@gmail.com>
---
.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 ++++++
.../drm/amd/display/dc/link/link_detection.c | 43 +++++++++++++++++++
2 files changed, 55 insertions(+)
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 13823469fa7c..49ee516dc83d 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7077,6 +7077,18 @@ amdgpu_dm_connector_poll(struct amdgpu_dm_connector
*aconnector, bool force)
enum dc_connection_type conn_type = dc_connection_none;
enum drm_connector_status status = connector_status_disconnected;
+ /* When the EDID is missing on an analog connector, that means
+ * we determined the connection using DAC load detection.
+ * In this case do NOT poll the connector do detect disconnect
+ * because that would run DAC load detection again which can cause
+ * visible visual glitches.
+ *
+ * Only allow to poll such a connector again when forcing.
+ */
+ if (!force && link->local_sink && link->local_sink->edid_caps.analog &&
+ !aconnector->drm_edid)
+ return connector->status;
+
mutex_lock(&aconnector->hpd_lock);
if (dc_link_detect_connection_type(aconnector->dc_link, &conn_type) &&
diff --git a/drivers/gpu/drm/amd/display/dc/link/link_detection.c
b/drivers/gpu/drm/amd/display/dc/link/link_detection.c
index fcabc83464af..6dd96e2797f4 100644
--- a/drivers/gpu/drm/amd/display/dc/link/link_detection.c
+++ b/drivers/gpu/drm/amd/display/dc/link/link_detection.c
@@ -1073,6 +1073,20 @@ static bool detect_link_and_local_sink(struct dc_link
*link,
break;
case EDID_NO_RESPONSE:
DC_LOG_ERROR("No EDID read.\n");
+
+ /* Analog connectors without EDID.
+ * This can be an old monitor that actually doesn't
have EDID,
+ * or could be a cheap DVI/VGA adapter that doesn't
connect DDC,
+ * and therefore we can't read the EDID.
+ */
+ if (link->link_enc->connector.id == CONNECTOR_ID_VGA ||
+ link->link_enc->connector.id ==
CONNECTOR_ID_DUAL_LINK_DVII ||
+ link->link_enc->connector.id ==
CONNECTOR_ID_SINGLE_LINK_DVII) {
+ DC_LOG_INFO("%s detected analog display without
EDID\n", __func__);
+ sink->edid_caps.analog = true;
+ break;
+ }
+
/*
* Abort detection for non-DP connectors if we have
* no EDID
@@ -1280,6 +1294,30 @@ static bool link_detect_ddc_probe(struct dc_link *link)
return true;
}
+static bool link_detect_dac_load_detect(struct dc_link *link)
+{
+ struct dc_bios *bios = link->ctx->dc_bios;
+ struct link_encoder *link_enc = link->link_enc;
+ enum engine_id engine_id = link_enc->preferred_engine;
+ enum dal_device_type device_type = DEVICE_TYPE_CRT;
+ enum bp_result bp_result;
+ uint32_t enum_id;
+
+ switch (engine_id) {
+ case ENGINE_ID_DACB:
+ enum_id = 2;
+ break;
+ case ENGINE_ID_DACA:
+ default:
+ engine_id = ENGINE_ID_DACA;
+ enum_id = 1;
+ break;
+ }
+
+ bp_result = bios->funcs->dac_load_detection(bios, engine_id,
device_type, enum_id);
+ return bp_result == BP_RESULT_OK;
+}
+
/**
* Determines if there is an analog sink connected.
*/
@@ -1296,6 +1334,11 @@ static bool link_detect_analog(struct dc_link *link,
enum dc_connection_type *ty
return true;
}
+ if (link_detect_dac_load_detect(link)) {
+ *type = dc_connection_single;
+ return true;
+ }
+
*type = dc_connection_none;
return true;
}
--
2.50.1
