[Freedreno] [PATCH v3] drm/msm/dp: force link training for display resolution change

[Dmitry Baryshkov]

On Fri, 27 May 2022 at 19:08, Kuogee Hsieh <quic_khsieh at 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 at 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;
>
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>


-- 
With best wishes
Dmitry