[Intel-gfx] [PATCH 2/2] drm/i915/dp: Fix LTTPR vswing/pre-emp setting in non-transparent mode

[Ville Syrjälä]

On Tue, Dec 29, 2020 at 07:22:01PM +0200, Imre Deak wrote:
> The DP PHY vswing/pre-emphasis level programming the driver does is
> related to the DPTX -> first LTTPR link segment only. Accordingly it
> should be only programmed when link training the first LTTPR and kept
> as-is when training subsequent LTTPRs and the DPRX. For these latter
> PHYs the vs/pe levels will be set in response to writing the
> DP_TRAINING_LANEx_SET_PHY_REPEATERy DPCD registers (by an upstream LTTPR
> TX PHY snooping this write access of its downstream LTTPR/DPRX RX PHY).
> The above is also described in DP Standard v2.0 under 3.6.6.1.
> 
> While at it simplify and add the LTTPR that is link trained to the debug
> message in intel_dp_set_signal_levels().
> 
> Fixes: b30edfd8d0b4 ("drm/i915: Switch to LTTPR non-transparent mode link training")
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c       |  2 +-
>  .../drm/i915/display/intel_dp_link_training.c | 19 +++++++++++--------
>  .../drm/i915/display/intel_dp_link_training.h |  3 ++-
>  3 files changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 88a6033d6867..16c563f1a515 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -6057,7 +6057,7 @@ static void intel_dp_process_phy_request(struct intel_dp *intel_dp,
>  
>  	intel_dp_autotest_phy_ddi_disable(intel_dp, crtc_state);
>  
> -	intel_dp_set_signal_levels(intel_dp, crtc_state);
> +	intel_dp_set_signal_levels(intel_dp, crtc_state, DP_PHY_DPRX);
>  
>  	intel_dp_phy_pattern_update(intel_dp, crtc_state);
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> index 7876e781f698..d8c6d7054d11 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -335,21 +335,24 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
>  }
>  
>  void intel_dp_set_signal_levels(struct intel_dp *intel_dp,
> -				const struct intel_crtc_state *crtc_state)
> +				const struct intel_crtc_state *crtc_state,
> +				enum drm_dp_phy dp_phy)
>  {
>  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
>  	u8 train_set = intel_dp->train_set[0];
> +	char phy_name[10];
>  
> -	drm_dbg_kms(&dev_priv->drm, "Using vswing level %d%s\n",
> +	drm_dbg_kms(&dev_priv->drm, "Using vswing level %d%s, pre-emphasis level %d%s, at %s\n",
>  		    train_set & DP_TRAIN_VOLTAGE_SWING_MASK,
> -		    train_set & DP_TRAIN_MAX_SWING_REACHED ? " (max)" : "");
> -	drm_dbg_kms(&dev_priv->drm, "Using pre-emphasis level %d%s\n",
> +		    train_set & DP_TRAIN_MAX_SWING_REACHED ? " (max)" : "",
>  		    (train_set & DP_TRAIN_PRE_EMPHASIS_MASK) >>
>  		    DP_TRAIN_PRE_EMPHASIS_SHIFT,
>  		    train_set & DP_TRAIN_MAX_PRE_EMPHASIS_REACHED ?
> -		    " (max)" : "");
> +		    " (max)" : "",
> +		    intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)));
>  
> -	intel_dp->set_signal_levels(intel_dp, crtc_state);
> +	if (intel_dp_phy_is_downstream_of_source(intel_dp, dp_phy))
> +		intel_dp->set_signal_levels(intel_dp, crtc_state);

The function name is a bit misleading now I guess since we're not
actually setting the signal levels here for the LTTPRs. But since
the debug print is here I guess we want to still call this. And as
usual I can't think of a better name for this, so I'm willing
to accept that slight inconsistency.

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

>  }
>  
>  static bool
> @@ -359,7 +362,7 @@ intel_dp_reset_link_train(struct intel_dp *intel_dp,
>  			  u8 dp_train_pat)
>  {
>  	memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
> -	intel_dp_set_signal_levels(intel_dp, crtc_state);
> +	intel_dp_set_signal_levels(intel_dp, crtc_state, dp_phy);
>  	return intel_dp_set_link_train(intel_dp, crtc_state, dp_phy, dp_train_pat);
>  }
>  
> @@ -373,7 +376,7 @@ intel_dp_update_link_train(struct intel_dp *intel_dp,
>  			    DP_TRAINING_LANE0_SET_PHY_REPEATER(dp_phy);
>  	int ret;
>  
> -	intel_dp_set_signal_levels(intel_dp, crtc_state);
> +	intel_dp_set_signal_levels(intel_dp, crtc_state, dp_phy);
>  
>  	ret = drm_dp_dpcd_write(&intel_dp->aux, reg,
>  				intel_dp->train_set, crtc_state->lane_count);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.h b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> index c3110c032bc2..6a1f76bd8c75 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> @@ -18,7 +18,8 @@ void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
>  			       enum drm_dp_phy dp_phy,
>  			       const u8 link_status[DP_LINK_STATUS_SIZE]);
>  void intel_dp_set_signal_levels(struct intel_dp *intel_dp,
> -				const struct intel_crtc_state *crtc_state);
> +				const struct intel_crtc_state *crtc_state,
> +				enum drm_dp_phy dp_phy);
>  void intel_dp_start_link_train(struct intel_dp *intel_dp,
>  			       const struct intel_crtc_state *crtc_state);
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp,
> -- 
> 2.25.1

-- 
Ville Syrjälä
Intel