[PATCH 28/45] drm/msm/dp: add an API to initialize MST on sink side

[Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>]

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@xxxxxxxxxxx>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index e69cdfbbe10484e47475ef189849f8ff6628bd7a..033d238e956263c1212fce45aab01316ef341edb 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -380,6 +380,35 @@ static int msm_dp_display_send_hpd_notification(struct msm_dp_display_private *d
 	return 0;
 }
 
+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_readb(dp->aux, DP_MSTM_CTRL, &old_mstm_ctrl);
+	drm_dp_dpcd_writeb(dp->aux, DP_MSTM_CTRL, 0);
+
+	/* add extra delay if MST state is not cleared */
+	if (old_mstm_ctrl) {
+		drm_dbg_dp(dp->drm_dev, "MSTM_CTRL is not cleared, wait %luus\n",
+			   clear_mstm_ctrl_timeout_us);
+		usleep_range(clear_mstm_ctrl_timeout_us,
+			     clear_mstm_ctrl_timeout_us + 1000);
+	}
+
+	ret = drm_dp_dpcd_writeb(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;
@@ -414,6 +443,9 @@ 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 > DEFAULT_STREAM_COUNT && msm_dp_panel_read_mst_cap(dp->panel))
+		msm_dp_display_mst_init(dp);
+
 	msm_dp_link_reset_phy_params_vx_px(dp->link);
 	rc = msm_dp_ctrl_on_link(dp->ctrl, dp_display->mst_active);
 	if (rc) {

-- 
2.34.1