[PATCH v4 29/39] drm/msm/dp: add an API to initialize MST on sink side

[Yongxing Mou <yongxing.mou@oss.qualcomm.com>]

From: Abhinav Kumar <quic_abhinavk@quicinc.com>

If the DP controller is capable of supporting multiple streams
then initialize the DP sink in MST mode by programming the DP_MSTM_CTRL
DPCD register to enable MST mode.

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 57 ++++++++++++++++++++++++++++++++-----
 1 file changed, 50 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 8ae690ce2b9f..abf26951819a 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -14,6 +14,7 @@
 #include <linux/string_choices.h>
 #include <drm/display/drm_dp_aux_bus.h>
 #include <drm/display/drm_hdmi_audio_helper.h>
+#include <drm/display/drm_dp_mst_helper.h>
 #include <drm/drm_edid.h>
 
 #include "msm_drv.h"
@@ -270,6 +271,40 @@ static int msm_dp_display_lttpr_init(struct msm_dp_display_private *dp, u8 *dpcd
 	return lttpr_count;
 }
 
+static void msm_dp_display_mst_init(struct msm_dp_display_private *dp)
+{
+	const unsigned long clear_mstm_ctrl_timeout_us = 100000;
+	u8 old_mstm_ctrl;
+	struct msm_dp *msm_dp = &dp->msm_dp_display;
+	int ret;
+
+	/* clear sink MST state */
+	drm_dp_dpcd_read_byte(dp->aux, DP_MSTM_CTRL, &old_mstm_ctrl);
+
+	ret = drm_dp_dpcd_write_byte(dp->aux, DP_MSTM_CTRL, 0);
+	if (ret < 0) {
+		DRM_ERROR("failed to clear DP_MSTM_CTRL, ret=%d\n", ret);
+		return;
+	}
+
+	/* add extra delay if MST old state is on*/
+	if (old_mstm_ctrl) {
+		drm_dbg_dp(dp->drm_dev, "wait %luus to set DP_MSTM_CTRL set 0\n",
+			   clear_mstm_ctrl_timeout_us);
+		usleep_range(clear_mstm_ctrl_timeout_us,
+			     clear_mstm_ctrl_timeout_us + 1000);
+	}
+
+	ret = drm_dp_dpcd_write_byte(dp->aux, DP_MSTM_CTRL,
+				     DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
+	if (ret < 0) {
+		DRM_ERROR("sink MST enablement failed\n");
+		return;
+	}
+
+	msm_dp->mst_active = true;
+}
+
 static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
 {
 	struct drm_connector *connector = dp->msm_dp_display.connector;
@@ -288,14 +323,19 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
 	if (rc)
 		goto end;
 
-	drm_edid = drm_edid_read_ddc(connector, &dp->aux->ddc);
-	drm_edid_connector_update(connector, drm_edid);
+	if (!(dp->max_stream > 1) || !drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd)) {
+		drm_edid = drm_edid_read_ddc(connector, &dp->aux->ddc);
+		drm_edid_connector_update(connector, drm_edid);
 
-	if (!drm_edid) {
-		DRM_ERROR("panel edid read failed\n");
-		/* check edid read fail is due to unplug */
-		if (!msm_dp_aux_is_link_connected(dp->aux))
-			return -ETIMEDOUT;
+		if (!drm_edid) {
+			DRM_ERROR("panel edid read failed\n");
+			/* check edid read fail is due to unplug */
+			if (!msm_dp_aux_is_link_connected(dp->aux))
+				return -ETIMEDOUT;
+		}
+
+		if (rc)
+			goto end;
 	}
 
 	msm_dp_link_process_request(dp->link);
@@ -317,6 +357,9 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
 	 */
 	msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
 
+	if (dp->max_stream > 1 && drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd))
+		msm_dp_display_mst_init(dp);
+
 	msm_dp_link_reset_phy_params_vx_px(dp->link);
 
 end:

-- 
2.43.0