Re: [PATCH 2/7] drm/msm/dp: reduce link rate if failed at link training 1

[khsieh@xxxxxxxxxxxxxx]

On 2021-07-08 00:33, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2021-07-06 10:20:15)
> > Reduce link rate and re start link training if link training 1
> > failed due to loss of clock recovery done to fix Link Layer
> > CTS case 4.3.1.7.  Also only update voltage and pre-emphasis
> > swing level after link training started to fix Link Layer CTS
> > case 4.3.1.6.
> >
> > Signed-off-by: Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/msm/dp/dp_ctrl.c | 86 
> > ++++++++++++++++++++++++++--------------
> >  1 file changed, 56 insertions(+), 30 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c 
> > b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > index 27fb0f0..6f8443d 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > @@ -83,13 +83,6 @@ struct dp_ctrl_private {
> >         struct completion video_comp;
> >  };
> >
> > -struct dp_cr_status {
> > -       u8 lane_0_1;
> > -       u8 lane_2_3;
> > -};
> > -
> > -#define DP_LANE0_1_CR_DONE     0x11
> > -
> >  static int dp_aux_link_configure(struct drm_dp_aux *aux,
> >                                         struct dp_link_info *link)
> >  {
> > @@ -1080,7 +1073,7 @@ static int dp_ctrl_read_link_status(struct 
> > dp_ctrl_private *ctrl,
> >  }
> >
> >  static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
> > -               struct dp_cr_status *cr, int *training_step)
> > +               u8 *cr, int *training_step)
> >  {
> >         int tries, old_v_level, ret = 0;
> >         u8 link_status[DP_LINK_STATUS_SIZE];
> > @@ -1109,8 +1102,8 @@ static int dp_ctrl_link_train_1(struct 
> > dp_ctrl_private *ctrl,
> >                 if (ret)
> >                         return ret;
> >
> > -               cr->lane_0_1 = link_status[0];
> > -               cr->lane_2_3 = link_status[1];
> > +               cr[0] = link_status[0];
> > +               cr[1] = link_status[1];
> >
> >                 if (drm_dp_clock_recovery_ok(link_status,
> >                         ctrl->link->link_params.num_lanes)) {
> > @@ -1188,7 +1181,7 @@ static void 
> > dp_ctrl_clear_training_pattern(struct dp_ctrl_private *ctrl)
> >  }
> >
> >  static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
> > -               struct dp_cr_status *cr, int *training_step)
> > +               u8 *cr, int *training_step)
> >  {
> >         int tries = 0, ret = 0;
> >         char pattern;
> > @@ -1204,10 +1197,6 @@ static int dp_ctrl_link_train_2(struct 
> > dp_ctrl_private *ctrl,
> >         else
> >                 pattern = DP_TRAINING_PATTERN_2;
> >
> > -       ret = dp_ctrl_update_vx_px(ctrl);
> > -       if (ret)
> > -               return ret;
> > -
> >         ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, pattern);
> >         if (ret)
> >                 return ret;
> > @@ -1220,8 +1209,8 @@ static int dp_ctrl_link_train_2(struct 
> > dp_ctrl_private *ctrl,
> >                 ret = dp_ctrl_read_link_status(ctrl, link_status);
> >                 if (ret)
> >                         return ret;
> > -               cr->lane_0_1 = link_status[0];
> > -               cr->lane_2_3 = link_status[1];
> > +               cr[0] = link_status[0];
> > +               cr[1] = link_status[1];
> >
> >                 if (drm_dp_channel_eq_ok(link_status,
> >                         ctrl->link->link_params.num_lanes)) {
> > @@ -1241,7 +1230,7 @@ static int dp_ctrl_link_train_2(struct 
> > dp_ctrl_private *ctrl,
> >  static int dp_ctrl_reinitialize_mainlink(struct dp_ctrl_private 
> > *ctrl);
> >
> >  static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
> > -               struct dp_cr_status *cr, int *training_step)
> > +               u8 *cr, int *training_step)
> >  {
> >         int ret = 0;
> >         u8 encoding = DP_SET_ANSI_8B10B;
> > @@ -1282,7 +1271,7 @@ static int dp_ctrl_link_train(struct 
> > dp_ctrl_private *ctrl,
> >  }
> >
> >  static int dp_ctrl_setup_main_link(struct dp_ctrl_private *ctrl,
> > -               struct dp_cr_status *cr, int *training_step)
> > +               u8 *cr, int *training_step)
> >  {
> >         int ret = 0;
> >
> > @@ -1496,14 +1485,14 @@ static int 
> > dp_ctrl_deinitialize_mainlink(struct dp_ctrl_private *ctrl)
> >  static int dp_ctrl_link_maintenance(struct dp_ctrl_private *ctrl)
> >  {
> >         int ret = 0;
> > -       struct dp_cr_status cr;
> > +       u8 cr_status[2];
> >         int training_step = DP_TRAINING_NONE;
> >
> >         dp_ctrl_push_idle(&ctrl->dp_ctrl);
> >
> >         ctrl->dp_ctrl.pixel_rate = 
> > ctrl->panel->dp_mode.drm_mode.clock;
> >
> > -       ret = dp_ctrl_setup_main_link(ctrl, &cr, &training_step);
> > +       ret = dp_ctrl_setup_main_link(ctrl, cr_status, 
> > &training_step);
> >         if (ret)
> >                 goto end;
>
> Do we need to extract the link status information from deep in these
> functions? Why not read it again when we need to?
>
> > @@ -1634,6 +1623,41 @@ void dp_ctrl_handle_sink_request(struct dp_ctrl 
> > *dp_ctrl)
> >         }
> >  }
> >
> > +static bool dp_ctrl_any_lane_cr_done(struct dp_ctrl_private *ctrl,
> > +                                       u8 *cr_status)
> > +
> > +{
> > +       int i;
> > +       u8 status;
> > +       int lane = ctrl->link->link_params.num_lanes;
> > +
> > +       for (i = 0; i < lane; i++) {
> > +               status = cr_status[i / 2];
> > +               status >>= ((i % 2) * 4);
> > +               if (status & DP_LANE_CR_DONE)
> > +                       return true;
> > +       }
> > +
> > +       return false;
> > +}
> > +
> > +static bool dp_ctrl_any_lane_cr_lose(struct dp_ctrl_private *ctrl,
> > +                                       u8 *cr_status)
> > +{
> > +       int i;
> > +       u8 status;
> > +       int lane = ctrl->link->link_params.num_lanes;
> > +
> > +       for (i = 0; i < lane; i++) {
> > +               status = cr_status[i / 2];
> > +               status >>= ((i % 2) * 4);
> > +               if (!(status & DP_LANE_CR_DONE))
> > +                       return true;
> > +       }
> > +
> > +       return false;
> > +}
>
> Why not use !drm_dp_clock_recovery_ok() for dp_ctrl_any_lane_cr_lose()?
ok,

> And then move dp_ctrl_any_lane_cr_done() next to
> drm_dp_clock_recovery_ok() and call it drm_dp_clock_recovery_any_ok()?
no understand how it work, can you elaborate it more?
> > +
> >  int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> >  {
> >         int rc = 0;
> > @@ -1641,7 +1665,7 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> >         u32 rate = 0;
> >         int link_train_max_retries = 5;
> >         u32 const phy_cts_pixel_clk_khz = 148500;
> > -       struct dp_cr_status cr;
> > +       u8 cr_status[2];
> >         unsigned int training_step;
> >
> >         if (!dp_ctrl)
> > @@ -1681,19 +1705,18 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> >                 }
> >
> >                 training_step = DP_TRAINING_NONE;
> > -               rc = dp_ctrl_setup_main_link(ctrl, &cr, 
> > &training_step);
> > +               rc = dp_ctrl_setup_main_link(ctrl, cr_status, 
> > &training_step);
> >                 if (rc == 0) {
> >                         /* training completed successfully */
> >                         break;
> >                 } else if (training_step == DP_TRAINING_1) {
> >                         /* link train_1 failed */
> > -                       if 
> > (!dp_catalog_link_is_connected(ctrl->catalog)) {
> > +                       if 
> > (!dp_catalog_link_is_connected(ctrl->catalog))
> >                                 break;
> > -                       }
> >
> >                         rc = dp_ctrl_link_rate_down_shift(ctrl);
> >                         if (rc < 0) { /* already in RBR = 1.6G */
> > -                               if (cr.lane_0_1 & DP_LANE0_1_CR_DONE) 
> > {
> > +                               if (dp_ctrl_any_lane_cr_done(ctrl, 
> > cr_status)) {
> >                                         /*
> >                                          * some lanes are ready,
> >                                          * reduce lane number
> > @@ -1709,12 +1732,15 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> >                                 }
> >                         }
> >                 } else if (training_step == DP_TRAINING_2) {
> > -                       /* link train_2 failed, lower lane rate */
> > -                       if 
> > (!dp_catalog_link_is_connected(ctrl->catalog)) {
> > +                       /* link train_2 failed */
> > +                       if 
> > (!dp_catalog_link_is_connected(ctrl->catalog))
> >                                 break;
> > -                       }
> >
> > -                       rc = dp_ctrl_link_lane_down_shift(ctrl);
> > +                       if (dp_ctrl_any_lane_cr_lose(ctrl, cr_status))
> > +                               rc = 
> > dp_ctrl_link_rate_down_shift(ctrl);
> > +                       else
> > +                               rc = 
> > dp_ctrl_link_lane_down_shift(ctrl);
> > +
> >                         if (rc < 0) {
> >                                 /* end with failure */
> >                                 break; /* lane == 1 already */
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
> > Forum,
> > a Linux Foundation Collaborative Project