Quoting Kuogee Hsieh (2022-06-14 14:05:02)
> Display resolution change is implemented through drm modeset. Older
> modeset (resolution) has to be disabled first before newer modeset
> (resolution) can be enabled. Display disable will turn off both
> pixel clock and main link clock so that main link have to be
> re-trained during display enable to have new video stream flow
> again. 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 a particular panel links status keep
> staying in sync for some period of time after main link had been shut
> down previously at display disabled. In this case, main link retraining
> will not be executed by irq_hdp_handle(). Hence video stream of newer
> display resolution will fail to be transmitted to panel due to main
> link is not in sync between host and panel.
>
> This patch will bypass irq_hpd_hanle() in favor of directly call
s/hanle/handle/
> dp_ctrl_on_stream() to always perform link training in regardless of
> main link status. So that no unexpected exception resolution change
> failure cases will happen. 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
>
> Changes in v4:
> -- revise commit text
>
> Changes in v5:
> -- fix spelling at commit text
>
> Changes in v6:
> -- split dp_ctrl_on_stream() for phy test case
> -- revise commit text for modeset
>
> Fixes: 62671d2ef24b ("drm/msm/dp: fixes wrong connection state caused by failure of link train")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/msm/dp/dp_ctrl.c | 31 +++++++++++++++++++++++--------
> drivers/gpu/drm/msm/dp/dp_ctrl.h | 3 ++-
> drivers/gpu/drm/msm/dp/dp_display.c | 13 ++++++-------
> 3 files changed, 31 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index af7a80c..cb9c7af 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1807,7 +1807,27 @@ 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_phy_test_report(struct dp_ctrl *dp_ctrl)
> +{
> + int ret = 0;
Drop assignment please.
> + struct dp_ctrl_private *ctrl;
> +
> + ctrl = container_of(dp_ctrl, struct dp_ctrl_private, dp_ctrl);
> +
> + ctrl->dp_ctrl.pixel_rate = ctrl->panel->dp_mode.drm_mode.clock;
> +
> + ret = dp_ctrl_enable_stream_clocks(ctrl);
> + if (ret) {
> + DRM_ERROR("Failed to start pixel clocks. ret=%d\n", ret);
> + return ret;
> + }
> +
> + dp_ctrl_send_phy_test_pattern(ctrl);
None of this code needs to be run in the normal display on case?
> +
> + return 0;
> +}
> +
> +int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl, bool force_link_train)
> {
> int ret = 0;
> bool mainlink_ready = false;
> @@ -1843,12 +1863,7 @@ int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl)
> goto end;
> }
>
> - if (ctrl->link->sink_request & DP_TEST_LINK_PHY_TEST_PATTERN) {
> - dp_ctrl_send_phy_test_pattern(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_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index c388323..b6d25ab 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1688,10 +1689,12 @@ 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);
> + force_link_train = true;
> + }
>
> - dp_display_enable(dp_display, 0);
> + dp_display_enable(dp_display, force_link_train);
Do we need to pass it from here? Why can't dp_display_enable() simply
check for 'state == ST_DISPLAY_OFF' and then force retrain the link?
