Commit ac1bb495 authored by Timur Kristóf's avatar Timur Kristóf Committed by Alex Deucher
Browse files

drm/amd/display: Use DAC load detection on analog connectors (v2) 



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.

Also, because the load detection causes visible glitches, do not
attempt to poll the connector again after it was detected this
way. Note that it will still be polled after sleep/resume or
when force is enabled, which is okay.

v2:
Add dc_connection_dac_load connection type.
Properly release sink when no display is connected.
Don't print error when EDID isn't read from an analog display.

Signed-off-by: default avatarTimur Kristóf <timur.kristof@gmail.com>
Reviewed-by: default avatarHarry Wentland <harry.wentland@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent d75e45b8

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

+10 −0
Original line number Diff line number Diff line
@@ -7248,6 +7248,16 @@ 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 we determined the connection using DAC load detection,

	 * 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->type == dc_connection_dac_load)

		return connector->status;



	mutex_lock(&aconnector->hpd_lock);



	if (dc_link_detect_connection_type(aconnector->dc_link, &conn_type) &&

drivers/gpu/drm/amd/display/dc/dc_types.h

+2 −1
Original line number Diff line number Diff line
@@ -353,7 +353,8 @@ enum dc_connection_type { 
	dc_connection_none,

	dc_connection_single,

	dc_connection_mst_branch,

	dc_connection_sst_branch

	dc_connection_sst_branch,

	dc_connection_dac_load

};



struct dc_csc_adjustments {

drivers/gpu/drm/amd/display/dc/link/link_detection.c

+60 −1
Original line number Diff line number Diff line
@@ -904,6 +904,37 @@ static bool link_detect_ddc_probe(struct dc_link *link) 
	return true;

}



/**

 * link_detect_dac_load_detect() - Performs DAC load detection.

 *

 * Load detection can be used to detect the presence of an

 * analog display when we can't read DDC. This causes a visible

 * visual glitch so it should be used sparingly.

 */

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;

}



/*

 * detect_link_and_local_sink() - Detect if a sink is attached to a given link

 *
@@ -1118,7 +1149,30 @@ static bool detect_link_and_local_sink(struct dc_link *link, 
			DC_LOG_ERROR("Partial EDID valid, abandon invalid blocks.\n");

			break;

		case EDID_NO_RESPONSE:

			/* Analog connectors without EDID:

			 * - old monitor that actually doesn't have EDID

			 * - cheap DVI-A cable or adapter that doesn't connect DDC

			 */

			if (dc_connector_supports_analog(link->link_id.id)) {

				/* If we didn't do DAC load detection yet, do it now

				 * to verify there really is a display connected.

				 */

				if (link->type != dc_connection_dac_load &&

					!link_detect_dac_load_detect(link)) {

					if (prev_sink)

						dc_sink_release(prev_sink);

					link_disconnect_sink(link);

					return false;

				}



				DC_LOG_INFO("%s detected analog display without EDID\n", __func__);

				link->type = dc_connection_dac_load;

				sink->edid_caps.analog = true;

				break;

			}



			DC_LOG_ERROR("No EDID read.\n");



			/*

			 * Abort detection for non-DP connectors if we have

			 * no EDID
@@ -1307,6 +1361,11 @@ 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_dac_load;

		return true;

	}



	*type = dc_connection_none;

	return true;

}
@@ -1328,7 +1387,7 @@ bool link_detect_connection_type(struct dc_link *link, enum dc_connection_type * 
	}



	/* Ignore the HPD pin (if any) for analog connectors.

	 * Instead rely on DDC.

	 * Instead rely on DDC and DAC.

	 *

	 * - VGA connectors don't have any HPD at all.

	 * - Some DVI-A cables don't connect the HPD pin.