drm/i915/dp: Reset the link params on HPD/connected boot/resume

The max link parameters should be set/reset only on HPD or
connected boot case or on system resume.

Add a flag reset_link_params to intel_dp to decide when
to reset the max link parameters. This prevents the parameters
from getting reset/overwritten through all other
connector->funcs->detect() calls. This is important when link
training fails and the max link params are modified to the
lower fallback values.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1486515251-23469-1-git-send-email-manasi.d.navare@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -4624,12 +4624,16 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 		      yesno(intel_dp_source_supports_hbr2(intel_dp)),
 		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
 
+	if (intel_dp->reset_link_params) {
 		/* Set the max lane count for sink */
 		intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
 
 		/* Set the max link BW for sink */
 		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
 
+		intel_dp->reset_link_params = false;
+	}
+
 	intel_dp_print_rates(intel_dp);
 
 	intel_dp_read_desc(intel_dp);
@@ -5010,6 +5014,8 @@ void intel_dp_encoder_reset(struct drm_encoder *encoder)
 	if (lspcon->active)
 		lspcon_resume(lspcon);
 
+	intel_dp->reset_link_params = true;
+
 	pps_lock(intel_dp);
 
 	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
@@ -5079,6 +5085,7 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
 		      long_hpd ? "long" : "short");
 
 	if (long_hpd) {
+		intel_dp->reset_link_params = true;
 		intel_dp->detect_done = false;
 		return IRQ_NONE;
 	}
@@ -5947,6 +5954,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 		 intel_dig_port->max_lanes, port_name(port)))
 		return false;
 
+	intel_dp->reset_link_params = true;
 	intel_dp->pps_pipe = INVALID_PIPE;
 	intel_dp->active_pipe = INVALID_PIPE;
 

drivers/gpu/drm/i915/intel_drv.h

@@ -933,6 +933,7 @@ struct intel_dp {
 	bool has_audio;
 	bool detect_done;
 	bool channel_eq_status;
+	bool reset_link_params;
 	enum hdmi_force_audio force_audio;
 	bool limited_color_range;
 	bool color_range_auto;