drm/amd/display: improve dpia pre-train

[WHY]
We see unstable DP LL 4.2.1.3 test result with dpia pre-train. It is
because the outbox interrupt mechanism can not handle HPD
immediately and require some improvement.

[HOW]
1. not enable link if hpd_pending is true.
2. abort pre-train if training failed and hpd_pending is true.
3. check if 2 lane supported when it is alt mode

Reviewed-by: Wenjing Liu <[email protected]>
Reviewed-by: Meenakshikumar Somasundaram <[email protected]>
Signed-off-by: Peichen Huang <[email protected]>
Signed-off-by: Tom Chung <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Peichen Huang

drivers/gpu/drm/amd/display/dc/dio/dcn31/dcn31_dio_link_encoder.c

@@ -653,8 +653,9 @@ void dcn31_link_encoder_get_max_link_cap(struct link_encoder *enc, struct dc_lin
 		if (!query_dp_alt_from_dmub(enc, &cmd))
 			return;
 
-		if (cmd.query_dp_alt.data.is_usb &&
-		    cmd.query_dp_alt.data.is_dp4 == 0)
+		if (cmd.query_dp_alt.data.is_dp_alt_disable == 0 &&
+				cmd.query_dp_alt.data.is_usb &&
+				cmd.query_dp_alt.data.is_dp4 == 0)
 			link_settings->lane_count = MIN(LANE_COUNT_TWO, link_settings->lane_count);
 
 		return;

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

@@ -2548,6 +2548,15 @@ void link_set_dpms_on(
 	if (pipe_ctx->stream->dpms_off)
 		return;
 
+	/* For Dp tunneling link, a pending HPD means that we have a race condition between processing
+	 * current link and processing the pending HPD. If we enable the link now, we may end up with a
+	 * link that is not actually connected to a sink. So we skip enabling the link in this case.
+	 */
+	if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA && link->is_hpd_pending) {
+		DC_LOG_DEBUG("%s, Link%d HPD is pending, not enable it.\n", __func__, link->link_index);
+		return;
+	}
+
 	/* Have to setup DSC before DIG FE and BE are connected (which happens before the
 	 * link training). This is to make sure the bandwidth sent to DIG BE won't be
 	 * bigger than what the link and/or DIG BE can handle. VBID[6]/CompressedStream_flag

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c

@@ -2312,6 +2312,14 @@ bool dp_verify_link_cap_with_retries(
 		} else {
 			link->verified_link_cap = last_verified_link_cap;
 		}
+
+		/* For Dp tunneling link, a pending HPD means that we have a race condition between processing
+		 * current link and processing the pending HPD. Since the training is failed, we should just brak
+		 * the loop so that we have chance to process the pending HPD.
+		 */
+		if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA && link->is_hpd_pending)
+			break;
+
 		fsleep(10 * 1000);
 	}