[PATCH v2 25/38] drm/msm/dp: add an API to initialize MST on sink side

[Yongxing Mou]

From: Abhinav Kumar <quic_abhin...@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_abhin...@quicinc.com>
Signed-off-by: Yongxing Mou <quic_yong...@quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
b/drivers/gpu/drm/msm/dp/dp_display.c
index 
5c8b38babc778f3575ab26ae4238b5f9fdb65b51..88cae0ca66015377e59bee757462edeae5ae91bf
 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"
@@ -390,6 +391,35 @@ 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_readb(dp->aux, DP_MSTM_CTRL, &old_mstm_ctrl);
+       drm_dp_dpcd_writeb(dp->aux, DP_MSTM_CTRL, 0);
+
+       /* 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_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;
@@ -431,6 +461,9 @@ 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->mst_supported && 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);
        rc = msm_dp_ctrl_on_link(dp->ctrl, dp_display->mst_active);
        if (rc) {

-- 
2.34.1