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

[Abhinav Kumar]

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_abhin...@quicinc.com>
---
 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