Messages in this thread | | | Date | Wed, 22 Jun 2022 10:26:39 +0300 | Subject | Re: [PATCH v8 1/2] drm/msm/dp: force link training for display resolution change | From | Dmitry Baryshkov <> |
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On 16/06/2022 20:09, Kuogee Hsieh wrote: > 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_handle() in favor of directly call > 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 > > Changes in v7: > -- drop 0 assignment at local variable (ret = 0) > > Changes in v8: > -- add patch to remove pixel_rate from dp_ctrl > > 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 | 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..01028b5 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_phy_test_report(&ctrl->dp_ctrl); > else > DRM_ERROR("failed to enable DP link controller\n"); > > @@ -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; > + 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;
Stephen has raised an interesting question. Comparing this to the dp_ctrl_on_stream(), he noticed that we do not halve the pixel clock here (if the wide bus is supported). So, the question is if this is correct or not.
> + > + 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); > + > + 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 */
-- With best wishes Dmitry
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