On Fri, 27 May 2022 at 19:08, Kuogee Hsieh quic_khsieh@quicinc.com wrote:

During display resolution changes display have to be disabled first followed by display enabling with new resolution. At current implementation, display enable function manually kicks up irq_hpd_handle which will read panel link status and start link training if link status is not in sync state. However, there is rare case that panel links status stay in synch which cause link training be skipped. Hence display resolution change failed.

This doesn't describe why resolution change fails if link training is skipped.

This patch force main link always be retrained during display enable procedure to prevent rare failed case from happening. Also this implementation are more efficient than manual kicking off irq_hpd_handle function.

Changes in v2: -- set force_link_train flag on DP only (is_edp == false)

Changes in v3: -- revise commit text -- add Fixes tag

Fixes: 62671d2ef24b ("drm/msm/dp: fixes wrong connection state caused by failure of link train") Signed-off-by: Kuogee Hsieh quic_khsieh@quicinc.com

---

drivers/gpu/drm/msm/dp/dp_ctrl.c | 6 +++--- drivers/gpu/drm/msm/dp/dp_ctrl.h | 2 +- drivers/gpu/drm/msm/dp/dp_display.c | 15 ++++++++------- 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c index af7a80c..bea93eb 100644 --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c @@ -1551,7 +1551,7 @@ static int dp_ctrl_process_phy_test_request(struct dp_ctrl_private *ctrl)

    ret = dp_ctrl_on_link(&ctrl->dp_ctrl);
    if (!ret)

•           ret = dp_ctrl_on_stream(&ctrl->dp_ctrl);
  

•           ret = dp_ctrl_on_stream(&ctrl->dp_ctrl, false);
    else
            DRM_ERROR("failed to enable DP link controller\n");
  
  

@@ -1807,7 +1807,7 @@ static int dp_ctrl_link_retrain(struct dp_ctrl_private *ctrl) return dp_ctrl_setup_main_link(ctrl, &training_step); }

-int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl) +int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl, bool force_link_train) { int ret = 0; bool mainlink_ready = false; @@ -1848,7 +1848,7 @@ int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl) return 0; }

•   if (!dp_ctrl_channel_eq_ok(ctrl))
  

•   if (force_link_train || !dp_ctrl_channel_eq_ok(ctrl))
            dp_ctrl_link_retrain(ctrl);
  
    /* stop txing train pattern to end link training */
  

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.h b/drivers/gpu/drm/msm/dp/dp_ctrl.h index 0745fde..b563e2e 100644 --- a/drivers/gpu/drm/msm/dp/dp_ctrl.h +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.h @@ -21,7 +21,7 @@ struct dp_ctrl { };

int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl); -int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl); +int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl, bool force_link_train); int dp_ctrl_off_link_stream(struct dp_ctrl *dp_ctrl); int dp_ctrl_off_link(struct dp_ctrl *dp_ctrl); int dp_ctrl_off(struct dp_ctrl *dp_ctrl); diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c index c388323..370348d 100644 --- a/drivers/gpu/drm/msm/dp/dp_display.c +++ b/drivers/gpu/drm/msm/dp/dp_display.c @@ -872,7 +872,7 @@ static int dp_display_enable(struct dp_display_private *dp, u32 data) return 0; }

•   rc = dp_ctrl_on_stream(dp->ctrl);
  

•   rc = dp_ctrl_on_stream(dp->ctrl, data);
    if (!rc)
            dp_display->power_on = true;
  
  

@@ -1654,6 +1654,7 @@ void dp_bridge_enable(struct drm_bridge *drm_bridge) int rc = 0; struct dp_display_private *dp_display; u32 state;

•   bool force_link_train = false;
  
    dp_display = container_of(dp, struct dp_display_private, dp_display);
    if (!dp_display->dp_mode.drm_mode.clock) {
  

@@ -1688,10 +1689,14 @@ void dp_bridge_enable(struct drm_bridge *drm_bridge)

    state =  dp_display->hpd_state;

•   if (state == ST_DISPLAY_OFF)
  

•   if (state == ST_DISPLAY_OFF) {
            dp_display_host_phy_init(dp_display);
  
  

•   dp_display_enable(dp_display, 0);
  

•           if (!dp->is_edp)
  

•                   force_link_train = true;
  

•   }
  

•   dp_display_enable(dp_display, force_link_train);
  
    rc = dp_display_post_enable(dp);
    if (rc) {
  

@@ -1700,10 +1705,6 @@ void dp_bridge_enable(struct drm_bridge *drm_bridge) dp_display_unprepare(dp); }

•   /* manual kick off plug event to train link */
  

•   if (state == ST_DISPLAY_OFF)
  

•           dp_add_event(dp_display, EV_IRQ_HPD_INT, 0, 0);
  

•   /* completed connection */
    dp_display->hpd_state = ST_CONNECTED;
  
  

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